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The replacement of small cations with bulkier organic cations containing long alkyl chains or benzene rings to form a thin two-dimensional (2D) perovskite passivation layer on three-dimensional (3D) perovskite (2D/3D) has become a promising strategy for improving both the efficiency and stability of perovskite solar cells (PSCs). The 2D layer defines the interfacial chemistry and physics at the 2D/3D bilayer and endows the 2D/3D structure with better chemical and thermal stability. Herein, 2D/3D (CF3-PEA)2FA0.85MA0.15Pb2I7/FA0.85MA0.15PbI3 planar heterojunction perovskite was produced using a facile interfacial ion exchange process. The 2D (CF3-PEA)2FA0.85MA0.15Pb2I7 capping layer can not only passivate the FA0.85MA0.15PbI3 film but also act as super-hydrophobic layer to inhibit water diffusion and significantly enhance the stability. The 2D capping layer can also establish a unique graded band structure at the perovskite/Spiro-OMeTAD interface and lead to p-type doping for Spiro-OMeTAD layer which is beneficial for efficient charge transport. Optimized PSCs based on this 2D/3D heterojunction yield a champion power conversion efficiency (PCE) of 23.1% and improved stability. The device maintains 84% output for 2400 h aging under ambient environmental conditions without encapsulation, and maintains 81% for 200 h under illumination with encapsulation. This work will inspire the design of more fluorinated 2D perovskite interfaces for advanced photovoltaics and beyond.

Solar energy is the centre of attention and major need of the world. The advancement in the photovoltaic devices plays the key role in the path of solar energy applications. The progress in the perovskite solar cell technologies in the direction of their theoretical power conversion efficiency necessitates elusive control above the carrier dynamics all over the whole device. In the present investigation, a comparative study via SCAPS simulation has been done for the optimization of the device in the light of high power conversion efficiency of organic–inorganic perovskite-based photovoltaic solar cells. Perovskite absorber layers CH3NH3PbI3 and CH3NH3SnI3 are sandwiched in between the TiO2 as electron transport layer (ETL) and spiro-OMeTAD as hole transport layer (HTL) to design the hetrostructures for the simulation. We have achieved enhancement in the power conversion efficiencies of both the devices as compared to the reported experimental and theoretical studies previously.

Lead free and environment friendly, light absorbing material is in high demand for the photovoltaic perovskite solar cell devices. The double perovskite La2NiMnO6 have the centre of attention for this demand. The present review is focused to discuss briefly the progress and challenges in the structural and magnetic properties of La2NiMnO6 in bulk, nano and thin film phases. The structural changes of La2NiMnO6 are highly interesting and have the direct correlation with the magnetic properties. On the basis of these transformations in the structure, efforts have been made to discuss several scientific progresses into technical novelties. This short review article is critically dedicated on reviewing the progresses, openings, and upcoming challenges in perovskite solar cell devices.

Nowadays solar cell is one of the best techniques for energy harvesting, we are using CH3NH3PbI3 perovskite material for solar cells applications. One of the most exciting developments in photovoltaics over recent years has been the emergence of perovskite (CH3NH3PbI3) as a promising new material for low-cost, high-efficiency photovoltaics. In this paper, we are assuming the layer of perovskite free from defects. A solar cell simulation software GPVDM, which works as a popular solar cell simulation tool (AMPS: Analysis of microelectronic and photonic structures) was used. The simulation model solves drift–diffusion of electron and hole, carrier continuity equations in position space to describe the movement of charge within the device, poison’s equation, and recombination of charge carriers.

In the conventional sandwich structure of perovskite solar cells (PSCs) with the metallic electrodes, the parasitic absorption losses due to the presence of glass substrate, conductive metal oxides and other functional layers below the perovskite film reduce a certain portion of photons that can be harvested by the perovskite absorber. The carbon quantum dots (CQDs) with down-converting properties can absorb high-energy UV light and convert them into the photons with lower energy lying in the visible light region. The CQDs can be used to enhance the light harvesting power of the PSCs so that the negative effect due to the parasitic absorption can be suppressed. In this work, a coating layer composed of CQDs is deposited on the illuminated side of the glass substrate. In contrast to our previous report, the deionized water (DIW) is used to disperse the CQDs instead of dispersing CQDs in the matrix of PMMA and chlorobenzene (CB). By using the new approach, the preparation of CQD coatings is more efficient and the use of toxic CB can be avoided. After systematic optimization of the preparation parameters, it is found that using water as the dispersion medium for CQDs can also yield the effective coatings for PSCs to enhance their light absorption power.

In this paper, using finite element method (FEM) as a three-dimensional simulation, the light trapping mechanism due to the use of plasmonic core/shell nanorod (PLCS-NR) array as well as its effect on absorption, generation, transfer of carriers and power conversion efficiency (PCE) in a perovskite solar cell (PSC) has been investigated. The short-circuit current density ( J sc ) increased due to the increase in the carrier generation rate in a PSC with a light-trapping architecture under the normal-angle sunlight (AM1.5G). Moreover, by choosing gold (Au) and silver (Ag) as the core and CuSCN as the shell in the PLCS-NR, the active layer (AL) absorption is increased compared to the planar structure. Using this proposed structure in the PSC can help improve the recombination rate and reduce it. The simulation results show that the device performance is highly dependent on the core and shell materials, and the height of the PLCS-NRs. Overall, an optimum height of 120 nm, a core radius of 10 nm, and Ag as the core were achieved for the PLCS-NRs in the PSC with J sc of 23.12 mA/cm2, the open-circuit voltage ( V oc ) of 1 V, and the PCE of 19.33%.

The development of dopant-free organic hole transport materials (HTMs) is critical to the commercialization of perovskite solar cells (PSCs). Indeed, dopants are the key determinants of reducing photovoltaic stability. Here, we designed and synthesized three mexylaminotriazine molecular glass derivatives containing triphenylamino moieties with an easy and low-cost process. All three compounds show good solubility and film-forming ability, and they show promising results as HTMs in PSCs. The PSCs fabricated with these mexyaminotriazine-substituted HTMs reach efficiencies up to (PCE) of 12.50% (12.40% stabilized Furthermore, we also measured the long-term stability of PSCs using these HTMs and the devices showed no significant decrease of their initial PCE after storage in the dark under an atmospheric environment with a relative humidity range of 40 to 50% for over 1000 h. This work indicates that methylaminotriazine derivatives are potential hole transport layer candidates for PSCs and provides strategic guidance for the further design of dopant-free HTMs.

Photoelectrochemical (PEC) water splitting over TiO2 photoanodes is a promising strategy for hydrogen production due to its eco-friendly, energy-saving, and low-cost nature. However, the intrinsic drawbacks of TiO2, i.e., the too wide band gap and rapid exciton recombination, significantly limit further enhancement of its performance. Herein, we report a TiO2 nanotube array (TNA), which is implanted by Cu ions and decorated by polymeric carbon nitride (PCN) nanosheets, as a photoanode for the high-efficiency PEC water splitting. In such designed material, Cu-ion implantation can effectively tailor the electronic structure of TiO2, thus narrowing the band gap and enhancing the electronic conductivity. Meanwhile, the PCN decoration induces TiO2/PCN heterojunctions, enhancing the visible light absorption and accelerating the exciton separation. Upon this synergistic effect, the modified TNA photoanode shows significantly improved PEC capability. Its photocurrent density, solar-to-hydrogen efficiency, and applied bias photon-to-current efficiency achieve 1.89 mA cm-2 at 1.23 VRHE (V vs reversible hydrogen electrode), 2.31%, and 1.20% at 0.46 VRHE, respectively. Importantly, this modified TNA supported on a meshlike Ti substrate can be readily integrated with a perovskite solar cell to realize unassisted PEC water splitting.

[6, 6]-phenyl C61butyric acid methyl ester (PC61BM) is a common fullerene derivative widely employed as an electron transport layer in inverted perovskite solar cells. However, major challenges such as interfacial recombination, current leakage and low mobility results in poor photovoltaic performance and stability for PC61BM-based devices. To overcome these issues, we demonstrated, for the first time, doping of the PC61BM with fullerene C60 to tailor the properties of the PC61BM. This doping approach helped to realize superior power conversion efficiency of perovskite solar cell with 17.46% versus pristine device with 14.20%. The C60 doped PC61BM reinforced the surface morphology of the PC61BM layer with reduced roughness and better coverage, up-shift of Fermi Level, higher electrical conductivity, higher maximum charge carrier generation rate, and higher charge collection probability. All these improvements contributed to reduced charge leakage at the interface, reduced charge recombination and promoted efficient charge transfer, transport, and collection. Furthermore, the enhanced hydrophobicity of the C60 doped PC61BM enabled superior ambient device stability compared to the pristine device. This work facilitates a simple and effective route to tailor perovskite solar cell performance towards higher efficiency and better stability.

Concentrated photovoltaic (CPV) has been identified as an effective method to further enhance the efficiency of photovoltaic cells. Previous studies on CPV mainly focused on III-V multi-junction cells. Nevertheless, III-V CPV technology is mainly used in niche applications due to its high cost. Here, we use metal-halide perovskite solar cell (PSC) to demonstrate a concentrated photovoltaic-thermoelectric tandem device. The thermoelectric generator (TEG) is utilized to reduce the effect of heat generation under concentrated solar irradiance. Our tandem system achieved a peak power conversion efficiency (PCE) of 25.0% at a solar concentration of 3 suns. This efficiency exceeded that of the single PSC by ~4.7%. Our work proves that by controlling the heat flow in concentrated PSC-TEG tandem system, the redundant heat produced by upper PSC can be effectively reused. This tandem structure provides a promising approach to improve the efficiency and stability of PSC under low-concentrated solar irradiation.

Titanium dioxide (TiO2) nanoparticles (NPs) were synthesized through solvothermal route by changing the rate of hydrolysis in the catalytic process. In order to change the hydrolysis rate, the concentration of acetic acid, as additive, was varied as 2 M, 3 M and 4 M. The synthesized NPs were examined by various physico-chemical characterization techniques. The powder X-ray diffraction (PXRD) analysis of the NPs reveals only the anatase phase of TiO2. The spherical shaped morphology of the NPs was observed in the high-resolution transmission electron microscopy (HR-TEM) analysis. The optical behaviour such as absorption, bandgap, diffuse reflectance and photoluminescence (PL) emission of the NPs were studied. The material's nature and behaviors were scrutinized and they were employed as photoanode in dye sensitized solar cell (DSSC) and as electron transport layer (ETL) in carbon-based perovskite solar cell (C-PSC). The charge transfer at the interface of the devices was studied with electrochemical impedance spectroscopy (EIS). The fabricated DSSC and C-PSC show highest power conversion efficiency (PCE) of 6.1% and 10.6%, respectively. The highest current collection was detected in C-PSC and the results are discussed in detail.

Cu2ZnSnS4 nanocrystal is a highly potential inorganic hole conducting material for perovskite solar cells employing low temperature carbon electrodes, which exhibit great prospect in future commercialization. However, Cu2ZnSnS4 nanocrystals are most commonly synthesized using the hot-injection method, which is not suitable for mass production. Here, a scalable one-step heating up synthesis method is demonstrated to successfully produce Cu2ZnSnS4 nanocrystals. First, the reaction time is optimized to be 60 min after evaluating the performances of perovskite solar cell employing the small-batch synthesized Cu2ZnSnS4 nanocrystals with different reaction time. Then, gram-scale Cu2ZnSnS4 nanocrystals are successfully synthesized under the optimized reaction time. Using these gram-scale synthesized Cu2ZnSnS4 nanoparticles, the best-performing perovskite solar cell can demonstrate a power conversion efficiency of 16.10%.

All-inorganic halide perovskite solar cells (PSCs) have acquired great progress, especially CsPbI2Br. However, their photoelectric conversion efficiency (PCE) remains far below the theoretical predictions. Non-radiative recombination is one of the important issues affecting the photoelectric performance of the PSCs, and the defective lead ions derived from the evaporation of halide ions in the inorganic perovskite are the principal non-radiative recombination centers. Herein, the non-radiative recombination is effectively suppressed by introducing the N-methyl-2-pyrrolidone (NMP) as a Lewis base molecule to passivate the defective lead ions. Therefore, by adjusting the dosage of NMP, the smooth and pinhole-free CsPbI2Br perovskite film is obtained and the optimized device exhibits a champion PCE of 16.77% with an excellent fill factor (FF) of 0.80. This work proves the effectiveness of passivation using Lewis base molecules to prevent non-radiative recombination defects in inorganic perovskite.

Various shaped nanostructures have been continually used in the antireflection of organic-inorganic hybrid perovskite solar cells. A full understanding of the shape-dependent light trapping behavior is the basis for finding the excellent broadband and omnidirectional photovoltaic performance. Hence, three-dimensional models of silica sphere, hemisphere, moth-eye and cone nanostructured perovskite solar cells were performed at omnidirectional angle in this work. We proposed electric field intensity per volume as a key parameter, verifying the transition of light trapping modes of several curved nanostructures from normal incidence to oblique incidence. As the incident angle increases, the antireflection effect of four curved structures becomes increasingly crucial, and the differences among them are also greater. Consequently, the moth-eye nanostructured perovskite solar cell has achieved the best photovoltaic performance considering omnidirectional incidence. The short-circuit current density is increased by 8.4% at normal incidence and increased by 36.4% at 60° incidence compared to the planar reference. Our work offers the theoretical analysis for omnidirectional antireflection structure optimization, and provides guidance for the experimental research and production of potential antireflection structures of solar cell.

Two-dimensional Ruddlesden–Popper (2DRP) metal halides have attracted extensive attention in photovoltaic applications due to their high stability, low self-doping levels and long-lived free carriers. Among them, (PA)2(MA)2Pb3I10 presents itself as a superior candidate, demonstrating greater moisture resistance and improved heat and light stability over many other 2DRP metal halides. This study takes on the opportunity to search for lead-free alternatives by investigating the optoelectronic and carrier transport properties, as well as the photovoltaic performance of such (PA)2(MA)2M3I10 type metal halides as the photovoltaic absorber, where M = Pb, Cd, Cr, Cu, Ge, Mn, Ni, Sn, Yb, Zn. Our results indicate that the bandgap of (PA)2(MA)2M3I10 can be tuned to the optimum photovoltaic application range of 0.9–1.6 eV, along with improved optical and enhanced photo-response capacity, when Sn, Cd, Mn, Ge, and Zn are used to replace Pb. In particular, (PA)2(MA)2Zn3I10 possesses the largest Stokes shift and Huang-Rhys factor, while showing the best photoluminescence tendency and broadest emission nature. (PA)2(MA)2Ge3I10 displays the most excellent of carrier transport capacities with high mobilities of 73 cm2 V−1 s−1 and 43 cm2 V−1 s−1 for electron and hole carriers, respectively, which are even comparable to that of 3D counterparts. Furthermore, (PA)2(MA)2Zn3I10 is predicted to have the highest power conversion efficiency of 23.36% based on an empirical energy loss (0.5 eV), which is quite close to the Shockley–Queisser limit, thereby featuring it as a suitable absorber for photovoltaic applications. These findings shed light on new strategies for designing and developing lead-free 2DRP metal halides targeted at future applications in photovoltaic solar cell devices.

In the current investigation, the plasmonic nano-cubes were used to improve the absorption of an organic-inorganic hybrid crystalline-based CH3NH3PbX3 perovskite solar cell. One of the critical challenges of plasmonic nanoparticles is their parasitic absorption that would compensate or even surpass the effect of plasmonic nanoparticles. So, the effects of parasitic absorption inside the nanoparticles were evaluated. By incorporating the plasmonic effect of nano-cubes, the parasitic absorption of Al and Ag nano-cubes and the absorption spectrum of the perovskite absorber were calculated. The parasitic absorption of nano-cubes was subtracted, and net absorption was obtained before calculating the photocurrents. Optimization is done to find the best nano-cubes edges and the period of the unit cell. Using Al and Ag nano-cubes increases the photocurrent increase to 23 mA/cm2, and 22 mA/cm2 in a cell with a thickness of 200 nm, respectively. The photocurrent of the reference cell is 17.70 mA/cm2. So, the enhancement factors of 29%, and 24.3% were obtained for them in comparison to the reference cell, respectively. Moreover, the boosted photon absorption was confirmed through the electrical field distribution and the profiles of generation rate. The results can be used to establish some guidelines for a realistic understanding of plasmonic resonance-based photovoltaic devices.

To boost the photoelectrochemical water oxidation performance of hematite photoanodes, high temperature annealing has been widely applied to enhance crystallinity, to improve the interface between the hematite-substrate interface, and to introduce tin-dopants from the substrate. However, when using additional dopants, the interaction between the unintentional tin and intentional dopant is poorly understood. Here, using germanium, we investigate how tin diffusion affects overall photoelectrochemical performance in germanium:tin co-doped systems. After revealing that germanium is a better dopant than tin, we develop a facile germanium-doping method which suppresses tin diffusion from the fluorine doped tin oxide substrate, significantly improving hematite performance. The NiFeOx@Ge-PH photoanode shows a photocurrent density of 4.6 mA cm−2 at 1.23 VRHE with a low turn-on voltage. After combining with a perovskite solar cell, our tandem system achieves 4.8% solar-to-hydrogen conversion efficiency (3.9 mA cm−2 in NiFeOx@Ge-PH/perovskite solar water splitting system). Our work provides important insights on a promising diagnostic tool for future co-doping system design., Germanium (Ge) has potential as a dopant suitable for the hematite-based photoelectrochemical water splitting system. Here, the authors report the fabrication of Ge doped porous hematite and demonstrate an efficient tandem system of Ge doped porous hematite and the perovskite solar cell.

Tungsten oxide (WOx) has been widely investigated due to mainly its optoelectronic properties. This study primarily aimed to examine the influence of oxygen concentration on the structural and optical properties of WOx films. Herein, WOx thin films have been prepared by reactive sputtering method at low power (50 W) while controlling the Ar:O2 gas flow rate to vary oxygen concentration. Energy Dispersive X-ray (EDX) analysis reveals that the oxygen concentration depends on the gas flow rate. Such oxygen concentration changes affect the film’s thickness, confirmed by the field emission scanning electron microscope (FESEM). Atomic force microscopy (AFM) analysis ensures the dependency of surface roughness of the films on the oxygen concentration. The developed films exhibit the amorphous state as validated by X-ray Diffraction (XRD) analysis. The Ultraviolet–Visible (UV–Vis) spectroscopy measurement was also conducted to determine transmittance and absorbance of the film, which further allows realizing necessary optical parameters, such as absorption coefficient, skin depth, energy bandgap, refractive index, extinction coefficient, etc. The oxygen concentration-dependent optical parameters are investigated in the spectral range of UV to near-infrared regions to ensure the use of WOx for optoelectronic device applications. Finally, we considered the optimized WOx film as a potential electron transport layer (ETL) to realize an efficient perovskite solar cell. The optics and optimization of this solar cell were studied by finite-difference time-domain (FDTD) simulations. The investigation allows us to calculate the maximum quantum efficiency (QE) and short-circuit current density (JSC) of ~90% and 22.1 mA/cm2, respectively.

One of the key parts of perovskite solar cells which has great influence on their performance and stability is hole transporting layer. Spiro-OMeTAD is extensively used as organic hole transporting material in perovskite solar cells. However, Spiro-OMeTAD is expensive and has low chemical stability. In this study, the solution processed Sb2S3 and Cu3SbS4 nanocrystals have been synthesized and then the n-i-p mesoscopic perovskite solar cells have been fabricated using Spiro-OMeTAD, Sb2S3 and Cu3SbS4 nanocrystals as hole transporting layer at ambient air condition. It is shown that the conduction and valence band levels of the synthesized Sb2S3 and Cu3SbS4 nanocrystals are in the proper positions for using them as hole transporting layer in the perovskite solar cells. The perovskite solar cells fabricated using the Sb2S3 and Cu3SbS4 nanocrystals as hole transporting layer show maximum power conversion efficiency of 8.2% and 13%. Moreover, the non-encapsulated perovskite solar cell with the Cu3SbS4 nanocrystals demonstrates 75% of its initial efficiency while the perovskite solar cell with Spiro-OMeTAD demonstrates 50% of its initial efficiency after 90 days under controlled humidity (

Perovskite solar cells show excellent power conversion efficiencies, long carrier diffusion lengths and low recombination rates. This encourages a view that intragrain defects are electronically benign with little impact on device performance. In this study we varied the methylammonium (MA)/formamidinium (FA) composition in MA1–xFAxPbI3 (x = 0–1), and compared the structure and density of the intragrain planar defects with device performance, otherwise keeping the device nominally the same. We found that charge carrier lifetime, open-circuit voltage deficit and current density–voltage hysteresis correlate empirically with the density and structure of {111}c planar defects (x = 0.5–1) and {112}t twin boundaries (x = 0–0.1). The best performance parameters were found when essentially no intragrain planar defects were evident (x = 0.2). Similarly, reducing the density of {111}c planar defects through MASCN vapour treatment of FAPbI3 (x ≈ 1) also improved performance. These observations suggest that intragrain defect control can provide an important route for improving perovskite solar cell performance, in addition to well-established parameters such as grain boundaries and interfaces. The role of intragrain planar defects in halide perovskite solar cell devices remains elusive. Now, Li et al. tune the composition of the perovskite layer to minimize the planar defect density and observe an improvement in the device performance.

Mixed halide perovskites with the ability to tune bandgaps exhibit attractive applications in tandem solar cells, building integrated photovoltaic and wavelength-tunable light-emitting devices. However, halide demixing under illumination or in the dark with a charge-carrier injection in both hybrid and inorganic perovskites results in bandgap instability and current-density-voltage (J-V) hysteresis, which can significantly hamper their application. Here, we demonstrate that halide segregation and J-V hysteresis in mixed halide inorganic CsPbIBr2 solar cells can be effectively mitigated by introducing an intermediate phase-enhanced Ostwald ripening through the control of the chemical composition in the CsPbIBr2 precursor solution. Excess amounts of either PbBr2 or CsI are incorporated into originally even molar amounts of PbBr2 and CsI precursor solutions. With the PbBr2-excess, we observed an enlarged perovskite grain size, no detectable halide phase segregation at the grain boundaries nor the perovskite/TiO2 interface, an increased minority carrier lifetime, a reduced J-V hysteresis, and an improved solar-cell performance. However, different CsI:PbBr2 stoichiometric ratios were found to have different effects on the performance of the perovskite solar cell. The excessive lead phase is reactive with the dimethyl sulfoxide (DMSO) in the precursor solution to form the Pb(I, Br)2-DMSO complex and the quasi-two-dimensional (2D) CsPb2(I, Br)5, which are conducive to Ostwald maturation and defect extinction. Finally, the CsPbIBr2 solar cell with a PbBr2-excess precursor composition reaches a power conversion efficiency (PCE) of 9.37% (stabilized PCE of 8.48%) and a maximum external quantum efficiency of over 90%.

Upscaling perovskite solar cell fabrication is one of the key challenges in the pathway for commercialization. The slow evaporation of frequently used solvents (DMF or DMSO) limits the fast perovskite layer crystallization, hindering their implementation in large scale deposition methods. Alternatively, methylamine-based precursors have demonstrated rapid crystallization, leading to uniform and specular films. Nonetheless, their application has been limited to MAPbI3 perovskites with limited efficiency and stability. In this work, we report the requirements for stabilizing α-phase of mixed cation perovskites with high amount of formamidinium by using a methylamine-based precursor. We found that even though, there are many methods for incorporating the methylamine (MA) in precursors or films; the MA content determines stabilization of the α-phase and therefore the viscous-solution route is the only method to incorporate high amounts of MA. At low amounts of MA, perovskite tend to crystallize in 1D dimensional FA3(MA)PbI5 phases due to the incomplete solvation of the PbI6− clusters. In contrast, high MA ratio induces a full solvation of the clusters, leading to a rapid crystallization and a full stabilization of the active 3D α-phase. These results open a window in the development and understanding of new precursors for the fabrication of high efficient, stable and scalable perovskite devices.

In recent years perovskite solar cells (PSC) is emerging as dominant technology among the photovoltaic world. The higher power conversion efficiency, facile deposition & fabrication techniques are making them favorable for many commercial purposes. Till now, the efficiency of 25.2% had been achieved for solid and up to 19.5% for flexible perovskite solar cells. This advancement in perovskite photovoltaic technology is achieved via massive research over the engineering of different layers of the device. Charge transporting layer (CTL) is one of the most important layers, its modification, deposition, passivation and optimization are the main challenges to be considered while experimenting. They are the interfaces among the contacts and the active layer, so, are crucial as they had to efficiently extract and transport the charges along with minimizing the traps between these layers. Here, the charge transporting layers based upon the nanomaterials of carbon and its derivatives are reported for different types of perovskite solar cells. These carbon-based nanomaterials not only enhance the power conversion efficiency and stability, but it also reduces the hysteresis loss. These materials include graphene-based materials, carbon nano tubes based and fullerene-based nanomaterials as CTL for perovskite solar cells. This review reports the use of carbon-based CTL in different forms for different types of perovskite solar cell applications.

Cesium lead iodide (CsPbI3) based perovskite solar cell (PSC) with inorganic electron and hole transport layers is simulated using SCAPS 1D to find optimum performance conditions for an all-inorganic PSC with maximum stability and efficiency. In this study, the absorption spectrum and bandgap of CsPbI3 absorber layer are computed with the help of density functional theory and the resulting spectrum is used as an input for device simulation. Further improvement of device performance is done by optimizing the work function of back electrode, absorber thickness, doping density as well as defect density. Under optimized conditions, a conversion efficiency of 11.99% is obtained with gold (Au) as back contact metal. The efficiency is enhanced to 15.6% for the FTO/ZnO/CsPbI3/CuSbS2/Se configuration, which uses Se instead of Au as back contact metal, indicating the possibility of replacing the expensive Au with Se as back contact metal in PSCs. The photovoltaic performance parameters achieve their maximum value at an absorber thickness of 547 nm and defect and dopant density of 2.07 × 1014 cm−3 and 1 × 1015 cm−3 respectively. The study shows that the PCE of inorganic CsPbI3 based PSCs can be improved significantly by introducing a low cost back contact metal Se and using inorganic transport materials, ZnO and CuSbS2.

Defect passivation has shown an essential role in improving the efficiency and stability of perovskite solar cells (PSCs). Herein, an efficient and low-cost π-conjugated sulfamic acid additive, 4-aminobenzenesulfonic acid (4-ABSA), is used to realize durable defect passivation of PSCs. The incorporation of 4-ABSA not only constructs a compact and smooth perovskite film but is also capable of passivating both negative- and positive-charged defects derived from under-coordinated lead and halogen ions. Besides, the π-conjugated system in 4-ABSA can induce preferred perovskite crystal orientation and stabilize the coordination effect between 4-ABSA and perovskite grains. As a result, the inverted planar PSC incorporated with 4-ABSA additives demonstrates an improved power conversion efficiency (PCE) from 18.25 to 20.32%. Moreover, this 4-ABSA passivation agent also enhances the stability of devices, which retains 83.5% of its initial efficiency under ambient condition at 60 °C after 27 days. This work provides a π-conjugated sulfamic acid for durable defect passivation of perovskite optoelectronic devices.

Organic-inorganic lead halide perovskite solar cells (PSCs) are highly efficient, flexible, lightweight, and even tolerant to radiation, such as protons, electron beams (EB), and γ-rays, all of which makes them plausible candidates for use in space satellites and spacecrafts. However, the mechanisms of radiation damage of each component of PSC [an organic hole transport material (HTM), a perovskite layer, and an electron transport material (ETM)] are not yet fully understood. Herein, we investigated the EB irradiation effect (100 keV, up to 2.5 × 1015 cm-2) on binary-mixed A site cations and halide perovskite (MA0.13FA0.87PbI2.61Br0.39, MA:methylammonium cation and FA:formaminidium cation), a molecular HTM of doped SpiroOMeTAD, and an inorganic ETM of mesoporous TiO2. Despite the decreased power conversion efficiency of PSCs upon EB exposure, the photoconductivities of the perovskite, HTM, and ETM layers remained intact. In contrast, significant dedoping of HTM was observed, as confirmed by steady-state conductivity, photoabsorption, and X-ray photoelectron spectroscopy measurements. Notably, this damage could be healed by exposure to short-wavelength light, leading to a partial recovery of the PSC efficiency. Our work exemplifies the robustness of perovskite against EB and the degradation mechanism of the overall PSC performance.

The perovskite solar cell technologies are the hope of satisfying the huge demand of tomorrow’s energy requirements. The inorganic, organic and mixed perovskite materials are the backbone of modern solar cells. The energy band gap and refractive index of perovskites help in selecting proper materials for solar cell, solid-state lighting and lasing applications. In this paper, various perovskite materials and different energy band gap–refractive index relations have been studied. A simple empirical relationship between energy gap ‘Eg’ and refractive index ‘n’ for perovskites has been developed and proposed. Using this relationship, refractive indices of 33 different perovskites have been calculated and compared with their reported values. Also, the refractive indexes of about 140 new perovskites have been predicted and reported probably for the first time. The researchers interested in refractive index calculation may use the proposed relation and need not to worry for complex experimental setup.

Tougher solar cell interfaces The low formation energies of the active layers in perovskite solar cells lead to low-toughness materials that are compliant and soft, which limits their interface stability and long-term reliability. Dai et al. show that treatment with iodine-terminated self-assembled monolayers that react with surface hydroxyl groups (which ultimately creates unwanted charge traps and voids) leads to a 50% increase of adhesion toughness between the electron transport layer and a mixed-composition perovskite thin film. The projected point at which 80% of the operating efficiency in perovskite solar cells was still retained increased from ∼700 to 4000 hours for 1-sun exposure with continuous maximum power point tracking. Science , this issue p. 618

The high trap-state density and low conductivity in compact TiO2 (c-TiO2) layer limits the power conversion efficiency (PCE) of organic-inorganic hybrid perovskite solar cells (HPSCs). Metal doping in c-TiO2 has been proven to be a successful strategy for enhancing the PCE of HPSCs. Herein, Zr is incorporated in the c-TiO2 layer with different doping concentrations, and its impact on the photovoltaic performance of methylammonium lead iodide (MAPbI3) HPSCs is investigated. Inclusion of Zr enhances the charge carrier collection at TiO2/perovskite junction as well as conductivity of TiO2 layer. It is demonstrated that Zr-doping reduces the dark current significantly by suppressing non-geminated recombinations, leakage path, and electron trap-states. As a result, the HPSCs with optimum Zr-doping (10 vol%) exhibits open-circuit voltage (VOC) of 1.076 V, short-circuit current density (JSC) of 23.57 mA cm−2, and PCE of 18.16% under one-sun illumination conditions. UV absorption confirms the increase in bandgap upon Zr-doping that leads to favorable band alignment with the perovskite layer. Further, the engineered solar cells are probed for current density-voltage (J-V) hysteresis, operational stability, leakage current, intensity-dependence behavior, and electrochemical impedance spectroscopy (EIS).

All-inorganic lead-free CsSnBr3 is attractive for applications in solar cells due to its nontoxicity and stability, but the device performance to date has been poor. Besides the intrinsic properties, impurities induced from electrodes may significantly influence the device performance. Here, we systematically studied the stability, transition energy levels, and diffusion of impurities from the most commonly used electrodes (Au, Ag, Cu, graphite, and graphene) in CsSnBr3 based on density functional theory calculations. Our results reveal that, whereas graphite and graphene electrodes exhibit negligible influence on CsSnBr3 due to the relatively high formation energies for carbon impurities in CsSnBr3, atoms from the metal electrodes can effectively diffuse into CsSnBr3 along interstice and form electrically active impurities in CsSnBr3. In this case, a significant amount of donor interstitial impurities, such as $$Ag_i^ +$$ A g i + , $$Cu_i^ +$$ C u i + , and $$Au_i^ +$$ A u i + , will be formed under p-type conditions, whereas the Sn-site substitutional acceptor impurities, namely $$Au_{Sn}^{2 - }$$ A u S n 2 − , $$Ag_{Sn}^{2 - }$$ A g S n 2 − , and $$Cu_{Sn}^{2 - }$$ C u S n 2 − , are the dominant impurities, especially under n-type conditions. In particular, except for $$Au_i^ +$$ A u i + , all these major impurities from the metal electrodes act as nonradiative recombination centers in CsSnBr3 and significantly degrade the device performance. Our work highlights the distinct behaviors of the electrode impurities in CsSnBr3 and their influence on the related devices and provides valuable information for identifying suitable electrodes for optoelectronic applications.

The crystal structure, electronic and optical properties of lead-free mixed halide inorganic perovskites, CsSnI3–xBrx (x = 0, 1, 2, 3), were studied within the framework of density functional theory. The effective electron-electron exchange correlation functional and, modified Becke–Johnson potential, were used for calculations of electronic and optical properties. The calculated optical parameters and the density of electronic states indicate that the CsSnI3–xBrx system has a property favorable for application in solar cells.

Achieving long‐term device stability is one of the most challenging issues that impede the commercialization of perovskite solar cells (PSCs). Recent studies have emphasized the significant role of the cathode interfacial layer (CIL) in determining the stability of inverted p‐i‐n PSCs. However, experimental investigations focusing on the influence of the CIL on PSC degradation have not been systematically carried out to date. In this study, a comparative analysis was performed on the PSC device stability by using four different CILs including practical oxides like ZnO and TiOx. A new implemented co‐doping approach was found to results in high device performance and enhanced device stability. The PSC with a thick film configuration of chemically modified TiOx CIL preserves over 77 % of its initial efficiencies of 17.24 % for 300 h under operational conditions without any encapsulation. The PSCs developed are among the most stable reported for methylammonium lead iodide (MAPbI3) perovskite compositions., In for the CIL: Highly stable inverted perovskite solar cells (PSCs) are assembled by using chemically modified titanium suboxide (TiOx) as the cathode interfacial layer (CIL). Codoping enhances the electrical properties of the TiOx CIL, providing better inner encapsulation with thick film configuration. The PSCs exhibit significantly improved operational stability, maintaining >77 % of their initial efficiencies for up to 300 h without encapsulation.

ABX3 perovskites offer the advantage of manipulating its properties by introducing multiple cations in B-site. Over the years, researchers used mixed B-site perovskites in oxide electronics to tune their electrical, magnetic properties. Here we used the triple cations at B-site in formamidinium based organometallic halide perovskite solar cell (PSC) in order to improve its degradation behavior with respect to heat and moisture. We synthesized halide based two hybrid perovskites viz., formamidinium sodium bismuth lead iodide [NH2CHNH2(Na0.25Bi0.25)Pb0.5I3] and formamidinium potassium bismuth lead iodide [NH2CHNH2(K0.25Bi0.25)Pb0.5I3] using solution chemistry. In order to decrease the content of toxic lead in these perovskites, trivalent bismuth was incorporated in the Pb-site. Monovalent sodium and potassium were used to maintain the charge neutrality of B-site, which has the formal valence of + 2 in these ABI3 type perovskites. Both of these perovskites showed reasonable optical band gaps with good charge carrier lifetime suggesting it as potential candidates for solar energy conversion and provisionally we achieved power conversion efficiency η = 0.52%. Moreover, superior thermal and moisture stability in these perovskites were observed in periodical structural and spectral analysis carried out by XRD, UV–Vis spectroscopy, time-correlated single photon counting (TCSPC) over the period of one month. Furthermore, ultrafast carrier dynamics in these perovskites were unraveled using femtosecond transient absorption studies. Our transient absorption kinetics data suggested more auger recombination and faster free electron-hole recombination process in FKBPI compared to FNBPI, which corroborates well with better energy conversion efficiency obtained in FNBPI based solar cell.

Compositional engineering with the addition of organic and inorganic cations is regarded as an effective way to improve the performance of perovskite solar cells (PSCs). However, exploration of triple-mixed cations in PSCs is still in its initial stage. In this study, triple cations of MA+, FA+, and Gua+ are mixed into perovskite and moulded into a 3D structure by the two-step deposition method, thus proving the feasibility of the triple-cation-based perovskite layer. Through the results of X-ray diffraction (XRD), scanning electron microscope (SEM), and Photoluminescence (PL) tests, Guay(FAMA)1-yPbIxCl3-x perovskite crystallisation was observed. The triple-mixed, cation-based perovskite film exhibits improved crystal quality, larger grain size, and fewer trap densities, all of which are positive for final power conversion efficiency (PCE) and stability. Based on the optimised MA+ and FA+ component ratio, the PSC showed the best performance with a GuaI doping concentration of 10%. The introduction of GuaI further improves the performance of devices by the passivation of defects and suppression of nonradiative recombination. The final PSCs displayed the best PCE (21.3%), as well as enhanced stability.

Here, we report on three new triphenylamine-based enamines synthesized by condensation of an appropriate primary amine with 2,2-diphenylacetaldehyde and characterized by experimental techniques and density functional theory (DFT) computations. Experimental results allow highlighting attractive properties including solid-state ionization potential in the range of 5.33-5.69 eV in solid-state and hole mobilities exceeding 10(-3) cm(2)/V.s, which are higher than those in spiro-OMeTAD at the same electric fields. DFT-based analysis points to the presence of several conformers close in energy at room temperature. The newly synthesized hole-transporting materials (HTMs) were used in perovskite solar cells and exhibited performances comparable to that of spiro-OMeTAD. The device containing one newly synthesized hole-transporting enamine was characterized by a power conversion efficiency of 18.4%. Our analysis indicates that the perovskite-HTM interface dominates the properties of perovskite solar cells. PL measurements indicate smaller efficiency for perovskite-to-new HTM hole transfer as compared to spiro-OMeTAD. Nevertheless, the comparable power conversion efficiencies and simple synthesis of the new compounds make them attractive candidates for utilization in perovskite solar cells.

The CuSCN-containing perovskite solar cells (PSCs) are presently of great research focus due to the high carrier mobility and well-aligned work function of the CuSCN hole-transporting layer. The improvement of photovoltaic performance and stability is still an important subject in the practical applications of CuSCN-containing PSCs. Herein, a facile approach to improve the efficiency and stability of CuSCN-containing PSCs is developed by spin-coating the triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode, such as linear macromolecule poly-TPD and branched macromolecule CRA-TPA. The maximum power conversion efficiency (PCE) of CuSCN-containing PSCs is increased by linear triphenylamine-based macromolecule poly-TPD to 10.36% while the PCE value of CuSCN-containing PSCs, being modified by branched triphenylamine-based macromolecule CRA-TPA, reaches up to 11.97%. Evidently, the PCE values are nearly two times higher than 5.95% of CuSCN-containing control device. The photovoltaic improvement of macromolecule-modified CuSCN-containing PSCs is mainly caused by the strong hole-transporting capacity of triphenylamine-based macromolecules inducing the reduction of charge recombination, which is derived from the reduced potential barrier of hole transportation including the flatness and coverage improvement in the triphenylamine-based macromolecular functional layer. In addition, the stability of macromolecule-modified CuSCN-containing PSCs is significantly improved due to the protection of triphenylamine-based macromolecular layer on the perovskite film, so that the unencapsulated macromolecule-modified CuSCN-containing PSC device can keep over 70–80% of initial PCE value after 20-day exposure under ambient environment (relative humidity (RH) = 50%, 25°C). This work provides a facile approach to enhance the efficiency and stability of CuSCN-containing PSCs through the modification of triphenylamine-based macromolecules between the CuSCN hole-transporting layer and metallic electrode.

Tin (Sn2+) and strontium (Sr2+), two potential alternatives to lead (Pb2+) in perovskite formation, were explored in transforming calcium carbonate (CaCO3) into a leaving group in a cation exchange reaction. This is the first part of a sequential ion exchange process in transforming calcite into a Pb-free perovskite material for perovskite solar cell applications. Calcite, a polymorph of CaCO3, was successfully transformed into strontianite (SrCO3) through a cation exchange reaction. In the Sn substitution reaction on the other hand, no SnCO3 formation was noted. Instead, oxides of Sn were formed. The wider spaces in between Ca2+ cations in (100) orientation account for the higher atomic Sn2+ and Sr2+ concentrations as compared to (001) orientation, where the cation movement is restricted. X-ray absorption and photoelectron spectroscopies were used to investigate the ion-exchange transformation of calcite towards the formation of an intermediate carbonate material. Graphic abstract

In this paper, we numerically investigated the effect of Bismuth iodide ( BiI 3 ) interfacial layer with different hole transport layer (HTL) candidates (including Spiro - O M e T A D , Cu 2 O , C u I , CuAlO 2 , CuSbS 2 , SrCu 2 O 2 , C u S C N , P T A A , P 3 H T ) in FAPI based perovskite (i.e., F A 0.85 Cs 0.15 P b I 0.85 Br 0.15 3 solar cells using Solar cell simulator capacitance software (SCAPS-1D). Our results reveal that the addition of a thin BiI 3 layer at the interface between the Perovskite active layer and the HTL efficiently improves hole extraction by defect passivation (i. e., reducing charge recombination and ion migration), which in turn enhances device performance compared to a typical reference architecture. The final optimized device photovoltaic parameters with interfacial layer confirm that the Cu -based HTL’s, especially Cu 2 O ( PCE = 24.07 % ) , and SrCu 2 O 2 ( PCE = 23.91 % ) HTL’s are more suitable for the F A 0.85 Cs 0.15 P b I 0.85 Br 0.15 3 solar cells than other HTL alternatives, including Spiro - O M e T A D due to higher hole mobility and the valence-band offset alignment between Perovskite/HTL interface. Also, the influence of several metal electrodes A g , C r , C u , A u , N i , P t is carefully studied with and without the BiI 3 interlayer. It is demonstrated that the energy band misalignment between the HTL and the metallic top electrode restricts charge collection, which is directly associated with low work functions. As a consequence, high work function electrodes such as Au , N i , and Pt have to be preferred in the presence or absence of the interlayer. The last section addresses the influence of the active layer, BiI 3 interlayer thicknesses on device performance and also the effect of parasitic resistances ( R series and R shunt ) were studied. From this analysis, BiI 3 interfacial layer seems highly beneficial for improving the performance of experimental perovskite solar cells.

Today Perovskite solar cell (PSC) has achieved efficiency close to 26%, surpassing the efficiencies of well- known Dye-Sensitized Solar cells (DSSC), CdTe-based solar cells, etc. Ease of preparing perovskite solutions and convenient deposition technique has given them added advantage over other contemporary competitors. This has also made them an economically feasible option. Since the inception of PSCs in 2009, a lot of improvements have been done in various aspects like composition, synthesis technique, fabrication method, and interface study. However, today it is crucial to think about the commercialization of PSCs. In this direction, the stability of PSCs has been a long-standing question. This review focuses on the key aspects of perovskite stability. Challenges posed by environmental factors like moisture, oxygen, temperature, and light are still unanswered. The lead toxicity of PSCs demands a potential substitute of lead with no compromise in their efficiency. The lead-free approach of PSCs and their commercialization has been discussed separately. A suitable emphasis has been given to the encapsulation of solar cells, as we find it a necessary part of the future commercialization process. This review has been addressed with an ideology to provide overall knowledge on the stability issues and challenges concerned with the PSCs, to attract young research community towards this emerging field.

Black orthorhombic (B-γ) CsSnI3 with low toxicity and excellent optoelectronic properties is a promising candidate for perovskite solar cell (PSC). However, the performance of the B-γ CsSnI3-based ...

Based on first-principles calculations, we propose a novel two-dimensional (2D) germanium carbide, tetrahex-GeC2, and determine its electronic and optical properties. Each Ge atom binds to four C atoms, in contrast to the known 2D hexagonal germanium carbides. Monolayer tetrahex-GeC2 possesses a narrow direct band gap of 0.89 eV, which can be effectively tuned by applying strain and increasing the thickness. Its electron mobility is extraordinarily high (9.5 × 104 cm2/(V s)), about 80 times that of monolayer black phosphorus. The optical absorption coefficient is ∼106 cm-1 in a wide spectral range from near-infrared to near-ultraviolet, comparable to perovskite solar cell materials. We obtain high cohesive energy (5.50 eV/atom), excellent stability, and small electron/hole effective mass (0.19/0.10 m0). Tetrahex-GeC2 turns out to be a very promising semiconductor for nanoelectronic, optoelectronic, and photovoltaic applications.

Halide exchange offers a versatile way to modify the properties of halide perovskites, but it is particularly challenging to slow the reaction rate to restrain defect growth in the products. Herein, we propose a slow halide exchange strategy to simultaneously fine-tune the optical and microstructural characteristics of CsPbIBr2 films by physically pairing CsPbIBr2 and CH3NH3PbI3 films. Once a proper heating treatment is applied, halide exchange of Br− and I− ions between the films is activated, and the reaction rate can be well controlled by the heating recipe, in which a high temperature can accelerate the exchange reaction, while a low temperature slows or stops it. By using an optimal halide exchange temperature (110°C) and time (2 h), the parent CsPbIBr2 film was transformed into high-quality CsPbI1+xBr2−x film, featuring an extended absorption onset from 590 to 625 nm, coarsened grains, improved crystallinity, reduced surface roughness, suppressed halide phase segregation, and identical stability to the pristine film. Accordingly, the efficiency of a carbon-based, all-inorganic perovskite solar cell (PSC) was boosted to 10.94%, which was much higher than that of the pristine CsPbIBr2 film (8.21%). The CsPbI1+xBr2−x PSC also possessed excellent tolerance against heat and moisture stresses.

We report on the successful growth optimization of an inorganic p-type copper oxide (Cu2O) thin films for various energy applications. First, Cu2O thin films of a typical thickness of 100 nm are deposited on fluorine-doped tin oxide (FTO) coated glass substrates by DC-reactive magnetron sputtering, followed by their in-depth characterization with different techniques, including scanning electron and atomic force microscopies, UV-Vis, X-ray diffraction and photoelectron spectroscopies, to probe their structural, optical, and morphological properties. Surface topology analysis revealed homogeneous, compact, and uniform sputtered deposited films. The as deposited films layers have shown a preferential crystal orientation of (111) and a stoichiometry of CuO, at the surface, which is believed to be mainly due to the oxidization effect of the non-capsulated surface, while a short-duration argon etching (~ 5 s) has revealed the growth of Cu2O films stoichiometry. Finally, during the reactive plasma deposition, films were grown under nitrogen gas flow to improve their hole-mobility, followed by a systematic annealing at various temperatures ranging from 100 to 250 °C to improve their crystalline structure. Hall effect measurement confirmed that the Cu2O thin film are p-type, with extremely high electronic properties, including an electrical conductivity of 2.6 × 102 S/cm, a hole mobility of about 30 cm2/Vs and a charge carrier density around 5 × 1019 cm-3, making them a serious candidate for a hole transport layer in perovskite solar cells.

Perovskite solar cells have continued to fascinate over the past decade due to fast increasing power conversion efficiency and very low fabrication cost but still suffered from poor stability. Interface engineering is evolved to be one of the most promising solutions to the instability problem. In this work, we perform a first-principles study on the MAPbI3/CsPbI3 interface system, aiming at clarifying the underlying mechanism of interfacial enhancement of solar cell performance. We devise the atomistic modeling of superlattices as increasing the number of included unit cells and carry out structural optimizations, revealing that the binding strength between the perovskite layers becomes stronger while the band gap decreases as the supercell size increases. Using enough large supercells of the interface system, we further estimate the formation energies of the interfacial vacancy defects and activation barriers for vacancy-mediated I atom migrations. Our calculations show the shallow transition states for most of the defects and the higher activation barriers for I atom migrations across the interface, providing an evidence of performance enhancement by the interface formation. By giving an insightful understanding of the MAPbI3/CsPbI3 heterojunction, this work definitely contributes to the design of interface systems for high-performance solar cells.

Pyridine molecules have been widely used to improve the performances of perovskite solar cells (PSCs). However, the effects of pyridine molecular structure, especially the functional group, on the defects passivation of perovskite solar cell have a lack of investigation. In this work, we introduced three pyridine molecules as additives into perovskite layer, including pyridine (PY), 4-methyl-pyridine (MP) and 4-tertbutyl pyridine (TBP), to investigate the influences of the molecular structure on the surface-defect passivation and long-term stability of perovskite solar cells. In fact, the pyridine molecules play two roles in the perovskite films. On the one hand, due to the different molecular structure, these pyridine molecules present differences in electron-pair-donor abilities (TBP > MP > PY), and then affect the interaction of pyridine molecule with Pb2+ in perovskite. Importantly, with the increase of interaction between different functional groups and Pb2+, the defect passivation effect was enhanced. What’s more, the crystal quality and light harvesting ability of the corresponding perovskite layer are improved by large crystal size and slow growth process. Consequently, PSCs with TBP, MP and PY respectively obtained a power conversion efficiency of 17.03%, 15.49% and 14.34%, which are higher than that of without additive (13.34%). On the other hand, owing to the hydrophobicity of groups, the pyridine molecules can enhance the moisture stability of devices. Significantly, the device based on the TBP-modified perovskite film exhibited improved moisture stability among the four type devices, owing to the best characteristic of the tertiary-butyl group with hydrophobicity in TBP.

Ferroelectric materials are promising for solar energy conversion due to the unique spontaneous polarization effect, leading to effective control of electron-hole recombination and potentially high power conversion efficiency of perovskite solar cells. Herein, the ultrathin ferroelectric hafnia alumina (HfAlO) films were obtained by atomic layer deposition and applied to modify the electron transport layer of PSCs. The XPS and AFM characterizations indicate that the Hf0.39Al0.10O films feature smooth, dense, and compact surface morphology. For the devices incorporating the ultrathin HfAlO films, the oriented ferroelectric effect-induced spontaneous polarization and internal electric field are crucial factors to enhance the charge separation during charge transfer. Accordingly, the short circuit current, open-circuit voltage, and power conversion efficiency (PCE) are increased by 11.8%, 9.0%, and 29.8%, respectively. Moreover, the HfAlO incorporating devices retained ~ 80% of the original PCE after 500 h ageing, much better than that of the pristine devices showing the retention of only ~ 50% of the original PCE.

This study entails a theoretical investigation of the effect of the hole transport layer (HTL) and electron transport layer (ETL) materials on a lead-free perovskite solar cell based on methylammonium tin iodide (CH3NH3SnI3). The simulations of the solar cells were conducted with the aid of the one-dimensional solar cell capacitance simulator, SCAPS-1D. The initial primary cell with the following architectural design: glass/FTO/WS2/CH3NH3SnI3/P3HT/Au, was simulated to yield a modest power conversion efficiency (PCE) of 10.47%. In an attempt to improve the PCE of this device, several materials were tested as the HTL, and their effects on the PCE were simulated. Subsequently, various ETL materials were tested with what were found to be the best possible HTL materials. The PCE of the primary device increased from 10.47% to over 16% with the utilization of 2,2′,7,7′-tetrakis [N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD), copper(I) oxide (Cu2O), copper(I) thiocyanate (CuSCN), copper(I) iodide (CuI), and poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno-[3,2-b]thiophene) (D-PBTTT-14) as HTLs. Tungsten disulfide (WS2) was shown to be the best suitable ETL material. The density of defects of the absorber for the devices with tungsten disulfide as the ETL and Cu2O, D-PBTTT-4, CuSCN, spiro-OMeTAD, and CuI as the HTLs, was best at 1.5 × 1017 cm−3, while for the primary device, the best value of the density of defects was 1.5 × 1014 cm−3. Furthermore, the energy barriers at the interface for primary and optimum devices was examined. Additionally, the effect of the external operating temperature on the performance of the devices was investigated. The simulation results allow one to propose the best HTL and ETL materials for high performance of lead-free perovskite solar cells, based on tin.

Formamidinium lead iodide (FAPbI3) is a category of perovskite material with an ideal band gap and high thermal stability, which can be efficiently prepared by two-step spin-coating. Spin-coating organic salts and transforming intermediate phase at the second step involves a components' reaction and state transition, thus playing a crucial role in the film quality formed afterward and optoelectronic properties of the fabricated perovskite solar cells (PSCs). In this paper, a cooling stage (CO) is used to post-treat the as-prepared precursor after the second spin-coating. The procedure of intermediate phase transferring to other state is found to be retarded; hence, the appearing velocity of perovskite nucleation is decreased. As a result, components react more adequately and larger perovskite grains with fewer defects are obtained; charge transport as well as carrier recommbination behaviors are therefore optimized. The PSCs based on the CO process achieved a champion power conversion efficiency (PCE) of 21.51% with enhanced stability. Moreover, CO treatment is observed to be beneficial for improving the film quality of perovskite in large-area preparation, which we anticipate can be further extended to the commercialized application of PSCs.

This article represents the study of physical, optical, and electrical properties Cesium Titanium (IV) based single halide Perovskite absorbing materials for the optimum photovoltaic application. The validity of the selected base parameters for the basic and absorbing materials of the proposed solar cell structure FTO/TiO2/Cs2TiX6/CuSCN/Ag where X is Br−, I−, Cl−, and F− has been used for that study. This article using the solar cell capacitance simulator—one-dimension (SCAPS-1D), has revealed the optimal solar cell device performance for the Perovskite materials (Cs2TiBr6, Cs2TiI6, Cs2TiCl6, and Cs2TiF6) thickness at 1.5, 1.0, 1.0, and 2.5 μm, respectively. The optimum device temperature and absorbing layer defect density was found to be 20 °C and 1010 cm−3 for all the four absorbing layer. The resonance time period and the indirect band gap for the Cs2TiBr6, Cs2TiI6, Cs2TiCl6, and Cs2TiF6 absorbing layer-based solar cell device is 0.53, 0.51, 0.51, 0.40, and 2.2, 2.1, 2.9, and 2.6 eV, respectively.

Perovskite solar cells have been studied extensively in the area of perovskite solar cells because they have a comparatively free hysteresis. Through fabrication of a perovskite solar cell based on a vanadium oxide buffer, this study clarified the mechanism of electron and hole transport in the laminated layer upon irradiation with light. The power conversion efficiency (PCE) of the Vanadium (Ⅳ) oxide (VO2) sputtering process device was approximately 13% and with the spin-coating process was 8.5%. To investigate the physicochemical origin of such PCE differences depending on the process type, comprehensive band alignment and band structure analyses of the actual cell stacks were performed using X-ray photoelectron spectroscopy depth measurements. Accordingly, it was found that the inconsistent valence band offset between the perovskite absorption layer and V2O5 layer as a function of the VO2 process type caused a difference in the hole transport, resulting in the difference in the efficiency.