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In this work, the device modeling of n-i-p architecture based on FTO/WSe2/ CsSn x Ge 1 - x I 3 x = 0.5 /Spiro-OMeTAD/Au was performed using solar cell capacitance simulator-one dimensional (SCAPS-1D) tool. All simulations were performed in the 1.5G AM sunlight spectrum. The effect of various parameters such as defect density, thickness of absorber layer and work function of contact electrode have been investigated. The effect of temperature, series and shunt resistance have also been analyzed. After optimization of photovoltaic parameters, we obtained power conversion efficiency 18.51%, fill factor 79.41%, open circuit voltage (Voc) 0.8458 V and short-circuit current density (Jsc) 27.562 mA/cm2. The modeling of CsSn x Ge 1 - x I 3 x = 0.5 based devices open the door for the fabrication of feasible and highly efficient perovskite solar cells. [ABSTRACT FROM AUTHOR]

The photovoltaic performances of n-i-p or inverted p-i-n BaSi2 homojunction solar cells are limited by the parasitic high light absorption of n-BaSi2 or p-BaSi2 window layer. In this work, diverse electron transport materials (ETMs) and hole transport materials (HTMs) are employed instead of BaSi2 as window layers to promote the performances of BaSi2 solar cells, and the effects of different ETMs and HTMs were simulated and comprehensively studied. For n-ETM/i-BaSi2/p-BaSi2 solar cells, the solar cell with ZnO exhibits the highest efficiency of 28.21%. As increasing the thicknesses of ETM layer from 5 nm to 100 nm, the efficiency for n-BaSi2/i-BaSi2/p-BaSi2 solar cell decreases seriously from 24.52% to 15.99%, while the solar cells with wide band gap ETMs including SnO2, TiO2 and ZnO show neglectable change in performances. The performances n-ETM/i-BaSi2/p-BaSi2 solar cells are affected by donor like defects more than acceptor like defects in i-BaSi2. For p-HTM/i-BaSi2/n-BaSi2 solar cells, employing Cu2O, CuI, CuSCN or NiO as HTM layer produces evident valence band discrepancies at HTM/i-BaSi2 interfaces. Heavy doping in HTM layer is necessary desired to overcome the energy band barriers. As increasing the thicknesses of HTM layer from 5 nm to 100 nm, the efficiency for p-BaSi2/i-BaSi2/n-BaSi2 solar cell also decreases from 24.52% to 15.99%, while the solar cells with wide band gap HTMs including CuI, CuSCN and NiO show neglectable change, and the efficiency for p-Cu2O/i-BaSi2/n-BaSi2 solar cells decreases slightly from 25.86% to 24.88%. The performances of p-HTM/i-BaSi2/n-BaSi2 solar cells are affected by acceptor like defects more than donor like defects in i-BaSi2. [ABSTRACT FROM AUTHOR]

• DFT and TD-DFT modelling and extensive analysis of eight carbazole-based molecules as HTMs in perovskite solar cells. • Deep HOMO energy levels guarantee proper alignment with the perovskite material. • Acceptor core groups enhance charge transport properties. • Flatness is beneficial when the core consisted of two cycles, particularly for MP 2 P 2 M. • MP 2 P 2 M is distinguished by its superior charge transfer properties. This study mainly focuses on DFT and TD-DFT modelling and extensive analysis of eight carbazole-based molecules (MM, MPM, MP 2. 5 M, MP 2. 6 M, MP 3. 5 M, MPPM, MP 2 P 2 M, and MP 3 P 3 M) as Hole Transporting Materials in Perovskite Solar cells. These compounds have in common the arm N3,N3,N6,N6-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine (M) characterized by its strong ability to carry holes, low cost, and good stability. The molecule MM presents two arms without acceptor core, while other compounds present two arms separated by different acceptor cores: phenyl, biphenyl, pyridine or bipyridine. All under-probe compounds were favored candidates for HTMs in perovskite solar cells due to their excellent HOMO delocalization, reduced hole reorganization energies, lower chemical reactivity, longer radiative lifetimes, and spontaneous solvation processes. Flatness proved beneficial when the core consisted of two cycles, particularly for MP 2 P 2 M. The results showed that the HOMO levels were primarily influenced by M fragments in most of the molecules, while the LUMO levels were distributed across both the carbazole units and the cores. All molecules exhibited a more stable LUMO compared to that of Spiro-OMETAD, with MP 2 P 2 M showing a notably stable level, resulting in a narrower gap. The study found that, except for MP 2 P 2 M, these materials did not interfere with the perovskite layer and effectively filled pores. The incorporation of acceptor core groups improved the conjugation backbone and electronic states, significantly enhancing charge transport properties, particularly in molecules with a double ring structure. Furthermore, adding a pyridine center greatly increased solubility, especially in MP 3 P 3 M, suggesting that acceptor core inclusion benefits the solubility of the investigated HTMs. The use of two rings core was shown to enhance light harvesting efficiency, boost photocurrent generation, and improve charge transfer performance, particularly in MP 2 P 2 M, which is distinguished by its superior flatness, solubility, and charge transfer properties. [ABSTRACT FROM AUTHOR]

In just a few years, the efficiency of perovskite-based solar cells (PSCs) has risen to 25.8%, making them competitive with current commercial technology. Due to the inherent advantage of perovskite thin films that can be fabricated using simple solution techniques at low temperatures, PSCs are regarded as one of the most important low-cost and mass-production prospects. The lack of stability, on the other hand, is one of the major barriers to PSC commercialization. The goal of this review is to highlight the most important aspects of recent improvements in PSCs, such as structural modification and fabrication procedures, which have resulted in increased device stability. The role of different types of hole transport layers (HTL) and the evolution of inorganic HTL including their fabrication techniques have been reviewed in detail in this review. We eloquently emphasized the variables that are critical for the successful commercialization of perovskite devices in the final section. To enhance perovskite solar cell commercialization, we also aimed to obtain insight into the operational stability of PSCs, as well as practical information on how to increase their stability through rational materials and device fabrication. [ABSTRACT FROM AUTHOR]

Perovskite Solar Cells (PSCs) being the most advanced photovoltaic technology today have attracted global attention due to its solution processability and cost effectiveness. In this paper, we reported the performance of perovskite solar cells by integrating Reduced Graphene Oxide (rGO) as a buffer layer. The combined effect of Ultraviolet visible (UV-vis) spectroscopy, X-ray Diffractometer (XRD), Raman spectroscopy, Scanning Electron Microscopy (SEM), Four Point Probe and Solar Simulator were used to explore the absorbance, crystallinity, morphological, resistivity and current voltage behavior of the photoanodes and devices. The rGO was deposited on top the mesoporous Titanium dioxide (m-TiO2) (Device B), on methylammonium lead triiodide (CH3NH3PbI3) perovskite absorber (Device C) and on m-TiO2 & CH3NH3PbI3 perovskite absorber (Device D). The reference device (Device A) was fabricated without rGO as a bench mark for comparison. From the results obtained, the devices with rGO show significant improvement over the device lacking rGO. The reference device gave a Short Circuit Current Density (Jsc) of 8.151 mAcm-2, Open Circuit Voltage (Voc) of 0.575 V, Fill Factor (FF) of 74.4 % and Power Conversion Efficiency (PCE) of 3.49 %. The best performing device was the one with rGO incorporated on both m-TiO2 and CH3NH3PbI3. The device gave a Jsc of 8.737 mAcm-2, Voc of 0.836 V, FF of 68.1% and PCE of 4.98 %. The device experienced an enhancement of ~7.20 % and 42.69 % in Jsc and PCE over the pristine device. This investigation aids the fundamental understanding of the effect of Graphene Materials (GRMs) on the optoelectronic properties of PSCs, and it further confirms the promising prospects of achieving low-cost, efficient and stable PSCs for commercialization with graphene materials. [ABSTRACT FROM AUTHOR]

• Five Phenothiazine-based hole transporting molecules were designed for efficient perovskite solar devices. • DFT calculations, structural geometrical analysis, and electronic properties were performed. • The molecules were found to be better hole-transporters for perovskite building blocks. • Improved VOC and power conversion efficiencies, indicating potential for future efficient PSCs devices. Perovskite solar cells are the emerging photovoltaics devices due to their high efficiency because of broad range light absorption and better charge carrier and separation properties. However, in the past few decades their material degradation and instability in the device operation accompanying low power conversion efficiency were the major drawbacks. To address these shortcomings, here we designed five Phenothiazine based novel hole-transporting molecules of d -Pi-A type with improved photovoltaic parameters for efficient perovskite solar devices. Detailed DFT calculation analysis with MPW1PW91 functions and 6–31 G basis set were performed for all molecules. Structural geometrical analysis along with density of states and transition density matrix analysis were extensively performed. Their electronic properties including HOMO and LUMO energies including energy gap, electron affinity, and ionization potential were also explored to elucidate the charge transfer characteristics. The lower values of reorganization in relation to reference molecules show that all designed molecules are better hole-transporters for perovskite building blocks. Lastly the devices photovoltaic parameter calculations for all the designed systems revealed that their Fill factor (FF), VOC and resultant power conversion efficiencies were significantly improved (18.63–22.81 % than its reference counterpart with PCE of 16.7 %) demonstrating their great potential for the future efficient PSCs devices. [ABSTRACT FROM AUTHOR]

Six materials were used as an interlayer at the anode side (anode interlayer [AIL]) of an archetypical planar heterojunction organic solar cell (OSC). In addition to two conventional wide bandgap hole transport materials (HTMs), tris(4‐carbazol‐9‐ylphenyl)amine (TCTA) and trans‐4,4′‐bis[N‐(naphthalen‐1‐yl)‐N‐phenylamino]stilbene (NPAE), we explore four narrow bandgap materials, bis(biphenylaminospiro)‐fumaronitrile (PhSPFN), bis(N‐(naphthalen‐1‐yl)‐N‐phenylamino)anthraquinone (NPAAnQ), bis‐(di(2‐fluorophenyl)aminospiro)‐fumaronitrile (FPhSPFN), and bis[4‐(N‐(pyren‐1‐yl)‐N‐phenylamino)phenyl]fumaronitrile (PyPAFN), the energy levels of which essentially align with the ones of SubPc, the active light‐absorbing material of the OSC study herein. By using a narrow bandgap AIL, universally enhanced short‐circuit current density and power conversion efficiencies (PCEs) have been achieved. In addition, one of these materials, FPhSPFN, results in a PCE of 5.13%, which is the highest reported value for SubPc solar cells with a similar architecture. This is ascribed to the formation of an otherwise passive exciton‐blocking interface. Furthermore, this demonstrates that charge selectivity by way of a high‐lying lowest unoccupied molecular orbital (LUMO) energy level is not a prerequisite for successful AIL design. As such, in terms of energy level alignment and bandgap energies, we establish a viable alternative approach toward interface and interlayer material design. [ABSTRACT FROM AUTHOR]

The strategy of ion doping in metal oxide is generally used to enhance the photoanode film feature, attain a suitable energy band and enhance carrier mobility. Here, a rare earth element erbium was doped into TiO 2 electron transport layer (ETL) by adding erbium trinitrate into the titanium precursor solution. In the present investigation, an attempt has been made to fabricate perovskite sensitized erbium doped TiO 2 nanoparticle (Er3+@TNPs) photoanode solar cell with different hole transport materials (HTMs) and graphite coated counter electrode. The perovskite sensitized solar cell (PSSC) built with CH 3 NH 3 SnI 3 sensitized Er3+@TNPs photoanode and spiro-MeOTAD HTM shows an impressive photovoltaic performance had the power conversion efficiency (PCE) of 11.54% when compared to the undoped TiO 2 photoanode PSSC. The results of this investigation indicate that the rare earth ion doping could be a promising method for producing effective ETL and enhanced performance PSSCs. • This work is mainly focused to increase the power conversion efficiency of photovoltaic devices using efficient photoanode structure, competence perovskite material with spiro-MeOTAD hole transport material. • The results showed in the present investigation, the device structure and the materials used in this study, significantly satisfied our focus of interest. [ABSTRACT FROM AUTHOR]

• Overview of CzDMPA based hole transporting materials (HTMs) for perovskite solar cells (PCSs) is discussed. • Classification of DMPA-containing carbazole based HTMs is given. • Research trends in synthetic pathways and structure-property relationship are reviewed. • Photovoltaic performance and stability in PCSs are summarized. Perovskite solar cells (PSC) based on metal-organic halide perovskites have emerged as one of the most promising photovoltaic technologies. Power conversion efficiency (PCE) has increased remarkably over the last few years from less than 10% up to certified efficiencies exceeding 23%. Selective interfacial layers play a critical role in charge extraction processes. In order to obtain high efficiencies, a hole transporting material (HTM) is required. Huge research efforts have been made to design efficient and low-cost materials. Carbazole-based HTMs are among the most promising new HTMs, in particular when they are substituted with dimethoxydiphenylamine (DMPA) units. This review gives an overview of the different classes of DMPA-containing carbazole-based HTMs and highlights the synthetic pathways, the structure-property relationship and the photovoltaic performances obtained in PSC devices. The relevance of structural variations and chemical doping processes is discussed with regard to efficiency and stability issues. [ABSTRACT FROM AUTHOR]

Abstract: The photovoltaic characteristics of CsBi3I10‐based solar cells with three dopant‐free hole‐conducting polymers are investigated. The effect on charge generation and charge recombination in the solar cells using the different polymers is studied and the results indicate that the choice of polymer strongly affects the device properties. Interestingly, for the solar cell with poly[[2,3‐bis(3‐octyloxyphenyl)‐5,8‐quinoxalinediyl]‐2,5‐thiophenediyl] (TQ1), the photon‐to‐current conversion spectrum is highly improved in the red wavelength region, suggesting that the polymer also contributes to the photocurrent generation in this case. This report provides a new direction for further optimization of Bi–halide solar cells by using dopant‐free hole‐transporting polymers and shows that the energy levels and the interaction between the Bi–halide and the conducting polymers are very important for solar cell performance. [ABSTRACT FROM AUTHOR]

In this study, six small carbazole-based molecules are investigated for usage as hole transport materials (HTMs) in perovskite solar cells. Among these compounds, two molecules based on 9-(4-(thiophen-2-yl)phenyl)-9H-carbazole thiophene-phenyle and carbazole (M 1 and M 2) were already synthesized, and four new molecules are designed by substituting carbazole, in positions 3,6 and 2,7, with methoxyphenyl (P 1 and P 2) and dimethoxyphenylamine (E 1 and E 2). Theoretical methods used in the calculations included density functional theory and time-dependent density functional theory. FMOs of all under-probe molecules are well positioned to ensure accurate alignment and prevent charge recombination at the perovskite material interface. The molecules' absorbance in the area below 404 nm shows that HTMs cannot compete with perovskite materials in an inverted configuration of a device. Reorganization energies indicate that M 1 , P 1,2 and E 1,2 are more favourable to be HTM, while M 2 shows a favourable electron transfer; it can be used as an electron transfer material (ETM). The results demonstrate that hole-electron couples can easily separate for any under-exanimated molecules, simplifying hole transport and enhancing the short-circuit (J SC). Additionally, DMPA-based molecules (E 1,2) may display chemical instability because of their poor hardness and the local distribution of charge in electrostatic potential maps. [ABSTRACT FROM AUTHOR]

We demonstrate for the first-time liquid exfoliated few layers of 2D Black phosphorus (BP) nanosheets as a hole transporting material (HTM) for perovskite based solar cells. The photoelectron spectroscopy in air (PESA) measurements confirm the low laying valence band level of BP nanosheets (−5.2 eV) favourable for hole injection from CH 3 NH 3 PbI 3 (MAPbI 3 ). Our results show that ∼25% improvement in power conversion efficiency (PCE) of η = 16.4% for BP nanosheets + Spiro-OMeTAD as an HTM as compared to spiro-OMeTAD (η = 13.1%). When BP nanosheets are exclusively utilised as an HTM, a PCE of η = 7.88% is noted, an improvement over the 4% PCE values observed for HTM free devices. Photoluminescence (PL) quenching of MAPbI 3 and impedance measurements further confirm the charge extraction ability of BP nanosheets. The structural and optical characterization of liquid exfoliated BP nanosheets is discussed in detail with the aid of transmission electron microscopy, Raman spectroscopy, absorption spectroscopy and photo-electron spectroscopy. [ABSTRACT FROM AUTHOR]

All-solid-state organic-inorganic halide perovskite solar cells (PSCs) have attracted wide attention due to the rapid progress of power conversion efficiency in recent years. Hole transport material (HTM) in PSCs plays the role of extracting and transporting photo-excited holes. Anisotropy of carrier mobility is one important property for semiconductors, however, which still remains unclear for the dominant HTM spiro-OMeTAD used in PSCs. Based on Density Functional Theory (DFT) and Marcus theory, we for the first time conducted investigations on the anisotropy of carrier mobility along representative crystal planes of spiro-OMeTAD by recombination energy λ and electronic coupling integral V . Results indicate that the holes and electrons show transport orientations consistency parallel to the (010), (101) and (111) crystal planes while inconsistency was found parallel to (100), (110), (011) and (001) crystal planes (with an angle ranged from 40° to 70° between the hole and electron transport directions). Our work embodies the theoretical significance of controllable and oriented fabrication of HTM in PSCs. [ABSTRACT FROM AUTHOR]

The organometal perovskite solar cells have shown stupendous development and have reached a power conversion efficiency (PCE) of 22.1%. However, the toxicity of lead in perovskite solar cells is a major challenge towards their incorporation into photovoltaic devices and thus needs to be addressed. Tin perovskite (CH3NH3SnI3) have attracted a lot of attention recently and could be a viable alternative material to replace lead perovskite in thin film solar cells. A detail understanding of effects of each component of a solar cell on its output performance is needed to further develop the technology. In this work, we performed a numerical simulation of a planar heterojunction tin based perovskite solar cell using SCAPS (Solar Cell Capacitance Simulator). Results revealed that thickness and defect density of the absorber material strongly influence the PCE of the device. Various types of hole transporting material (HTM) were compared and analysed to improve the performance of the solar cell. Parameters such as hole mobility and acceptor density of HTM also signified dependence on PCE of the device. These results indicate the possibility to design, fabricate and enhance the performance of tin based perovskite solar cells. [ABSTRACT FROM AUTHOR]

Emerging development in perovskite sensitized solar cell have ushered in a transformative shift in the evolution of efficient and low-cost solar cell technologies. The improvement represents significant progress in the performance of sensitized solar cells since their breakthrough in 1991. Existing unexplored opportunities with these new developments depicts potential platform to achieve higher efficiency. Earlier development in solid state dye sensitized solar cells (DSSCs) has led to the incorporation of novel semiconductor nanocrystalline quantum dots (QDs) and perovskite as alternative sensitizer to improve device stability and enhance absorption coefficient. The attractiveness of perovskite CH3NH3PbI3 as sensitizer for solar cell incorporates its cost-effectiveness and light-harvesting capability which has shown consistent improvement in device performance in recent years. The incorporation of metal chalcogenides into solid-state dye sensitized solar cells showed significant improvement in power conversion efficiency (PCE) of 18.05%. With CH3NH3PbX3 (X=Cl, Br, or I) as an alternative to dye, device performance has shown to be promising although emerging challenges require a prioritized concern. In this review, recent exciting improvements in the performance of perovskite solar cells were discussed and the fundamental mechanisms incorporated into the structural evolution leading to PCE of 20.8%. In addition, prospects overriding present challenges were proposed for future work toward practical realization of highly- efficient solar cell upon optimization. [ABSTRACT FROM AUTHOR]

One of the main obstacles to perovskite solar cells (PSCs) entering the market is the doping-induced degradation of expensive hole transport materials (HTMs), which results in poor device stability. Although lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-tert-butylpyridine (4-tBp) as additives are commonly used in HTMs, they often lead to low device stability and reproducibility due to their hygroscopic and volatile nature. In this study, we incorporated the dilithium phthalocyanine (Li 2 Pc) molecule into the Spiro-OMeTAD precursor solution with Li-TFSI and 4-tBp to produce triple-cation PSCs with an n–i–p configuration operating with high efficiency and stability. The addition of the Li 2 Pc molecule not only improves the perovskite/Spiro-OMeTAD interface but also increases the π–π stacking in the thin-film phase according to the absorption and Raman results. Based on space-charge-limited current, photoluminescence, time-resolved photoluminescence and lifetime analysis measurements, charge transfer is improved with the Li 2 Pc molecule and charge recombination losses are reduced. As a result, the control device showed a power conversion efficiency (PCE) of 20.0% with J SC = 24.6 mA/cm2 and fill factor (FF) = 72.7%, whereas the Li 2 Pc-doped device exhibited an improved PCE of 20.6% with J SC = 25.0 mA/cm2 and FF = 73.6%. The addition of Li 2 Pc resulted in more stable and high-efficiency solar cells that maintained approximately 90% of the initial efficiency after 40 days. [Display omitted] • The addition of the Li 2 Pc molecule can increase the π–π stacking in the thin-film phase. • Li 2 Pc can effectively passivate the defects at the triple-cation perovskite/Spiro-OMeTAD interface. • The efficiency of triple-cation perovskite solar cell is increased from 20.0% to 20.6%. • The device with Li 2 Pc retained about 90% of the initial efficiency after 40 days compared to the control device. [ABSTRACT FROM AUTHOR]

Effective engineering of surface ligands in semiconductor nanocrystals can facilitate the electronic interaction between the individual nanocrystals, making them promising for low-cost optoelectronic applications. Here, the use of high purity Cu2ZnSnS4 (CZTS) nanocrystals as the photoactive layer and hole-transporting material is reported in low-temperature solution-processed solar cells. The high purity CZTS nanocrystals are prepared by engineering the surface ligands of CZTS nanocrystals, capped originally with the long-chain organic ligand oleylamine. After ligand removal, CZTS nanocrystals show substantial improvement in photoconductivity and mobility, displaying also an appreciable photoresponse in a simple heterojunction solar cell architecture. More notably, CZTS nanocrystals exhibit excellent hole-transporting properties as interface layer in perovskite solar cells, yielding power conversion efficiency (PCE) of 15.4% with excellent fill factor (FF) of 81%. These findings underscore the importance of removing undesired surface ligands in nanocrystalline optoelectronic devices, and demonstrate the great potential of CZTS nanocrystals as both active and passive material for the realization of low-cost efficient solar cells. [ABSTRACT FROM AUTHOR]

Due to their uncommon electronic properties, carbon-based nanomaterials have led to extensive research efforts in the field of photovoltaic energy conversion in the last two decades. Initially exploiting carbon nanotubes, carbon-based solar cells have now largely taken benefit from graphene and its various forms to demonstrate significant improvements in almost all device functions including charge generation, charge collection, and charge transport. More recently, hybrid metalorganic halide perovskites became one of the most promising materials for third generation solar cells, with efficiencies now competing with thin film technologies. While several issues remain to be addressed regarding device operation and stability, the incorporation of carbon-based nanostructures was rapidly proposed, and significant advances have been achieved so far. In this work, we review the recent progresses made in the specific field of graphene-based perovskite solar cells. We especially emphasize the relevance of the approach applied to hole and electron transport media (HTM and ETM), electrodes, as well as approaches aiming at improving the stability of the device. Tandem architectures based on graphene interlayers will also be discussed, illustrating the broad potentialities of graphene materials in the development of the perovskite-based photovoltaic technology. [ABSTRACT FROM AUTHOR]

An attempt has been made to fabricate methyl ammonium tin chloride (CHNHSnCl) perovskite-sensitized TiO nanostructure photoanode solar cell with hole transport material (HTM) spiro-MeOTAD and graphite-coated counter electrode (CE). The TiO nanoparticles (TNPs), TiO nanoleaves (TNLs), and TNLs with MgO core/shell photoanodes were prepared to fabricate perovskite-sensitized solar cells (PSSCs). The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The photovoltaic characteristics of the PSSCs, photocurrent density ( J ), open-circuit voltage ( V ), fill factor (FF), and power conversion efficiency (PCE) were determined under illumination of AM 1.5 G. Electrochemical impedance spectroscopy (EIS) analysis was carried out to study the charge transport and lifetime of charge carriers at the photoanode-sensitizer-electrolyte interface of the PSSCs. The PSSC made with CHNHSnCl perovskite-sensitized TNL-MgO core/shell photoanode and spiro-MeOTAD HTM shows an impressive photovoltaic performance, with J = 17.24 mA/cm, V = 800 mV, FF = 73 %, and PCE = 9.98 % under 100 mW/cm light intensity. The advent of such simple solution-processed mesoscopic heterojunction solar cells paves the way to realize low-cost and high-efficiency solar cells. By the aid of electrochemical impedance spectroscopy, it is revealed that the core/shell structure can increase an interfacial resistance of the photoanode-CHNHSnCl interface and retard an electron recombination process in the photoanode-sensitizer-HTM interface. [ABSTRACT FROM AUTHOR]

Hybrid organometal halide perovskites have attracted much attention these past four years as the new active layer for photovoltaic applications. Researches are now intensively focused on the stability issues of these solar cells, the process of fabrication and the design of innovative materials to produce efficient perovskite devices. In this review, we highlight the recent progress demonstrated in 2015 in the design of new π-conjugated organic materials used as hole transporters in such solar cells. Indeed, several of these "synthetic metals" have been proposed to play this role during the last few years, in an attempt to replace the conventional 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) reference. Organic compounds have the benefits of low production costs and the abundance of raw materials, but they are also crucial components in order to address some of the stability issues usually encountered by this type of technology. We especially point out the main design rules to reach high efficiencies. [ABSTRACT FROM AUTHOR]

• Perovskite solar cells with device structure of FTO/TiO 2 /MAPbI 3 /GO + spiro-MeOTAD/Au has been developed. • GO + spiro-MeOTAD has been used as HTM. • PCE of 8.3% has been achieved using GO + spiro-MeOTAD as HTM. • The insertion of GO enhanced the stability of the perovskite solar cells. Herein, we reported the fabrication of perovskite solar cells (PSCs) with device architecture of FTO/TiO 2 /MAPbI 3 /GO + spiro-MeOTAD/Au. Graphene oxide (GO) was synthesized by Hummer's method which was further incorporated with spiro-MeOTAD to develop the stable PSCs. The fabricated PSCs device exhibited good efficiency of 8.3% using GO + spiro-MeOTAD/Au as hole-transport material (HTM) whereas control device (without GO) showed efficiency of 6.95%. PSCs device (with GO + spiro-MeOTAD) also exhibited good stability up to 168 h under controlled humidity (∼40–50%). [ABSTRACT FROM AUTHOR]

Hybrid organometal halide perovskites have attracted much attention these past four years as the new active layer for photovoltaic applications. Researches are now intensively focused on the stability issues of these solar cells, the process of fabrication and the design of innovative materials to produce efficient perovskite devices. In this review, we highlight the recent progress demonstrated in 2015 in the design of new π-conjugated organic materials used as hole transporters in such solar cells. Indeed, several of these “synthetic metals” have been proposed to play this role during the last few years, in an attempt to replace the conventional 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (Spiro-OMeTAD) reference. Organic compounds have the benefits of low production costs and the abundance of raw materials, but they are also crucial components in order to address some of the stability issues usually encountered by this type of technology. We especially point out the main design rules to reach high efficiencies.

In this study, DFT calculations carried out using Carbazole-based HTMs substituted with dimethoxy phenylamine units (DMPA) in positions 2,3,6,7 and 9 are coupled with the experimental results drawn from the literature. The most important challenge for us is to establish a link between the optoelectronic and structural properties of molecules and their performance as HTMs. In this work, we find that the important structural effect is generated by the pyridinic nucleus. The substituents linked to the nitrogen atom of carbazole do not contribute to HOMO or LUMO in most of the studied HTMs. Hence, apart from the illustrated performances, parameters as the contribution of such substituents to being attached to the perovskite, or to the cohesion of the HTM's molecules contributing to the perovskite stability all prove decisive. The 2,7 substitution favors more stabilization of LUMOs when compared to 3,6 substitution, which leads to a narrow gap for 2,7 homologous. This makes these 2,7-substituted molecules good candidates as light absorbent in Organic Solar cells. The differences in the solar cell performances using these HTMs is mostly linked to the effect of these groups on their intermolecular interactions on one hand, and on the interfacial contact between HTMs and perovskite on the other hand. [ABSTRACT FROM AUTHOR]

Copper oxide (CuxO) films are considered to be an attractive hole-transporting material (HTM) in the inverted planar heterojunction perovskite solar cells due to their unique optoelectronic properties, including intrinsic p-type conductivity, high mobility, low-thermal emittance, and energy band level matching with the perovskite (PS) material. In this study, the potential of reactive sputtered CuxO thin films with a thickness of around 100 nm has been extensively investigated as a promising HTM for effective and stable perovskite solar cells. The as-deposited and annealed films have been characterized by using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Photoluminescence (PL), UV-Vis spectroscopy, and Hall-effect measurement techniques. The significant change in structural and optoelectronic properties has been observed as an impact of the thermal annealing process. The phase conversion from Cu2O to CuO, including grain size increment, was observed upon thermal annealing. The transmittance and optical bandgap were found to vary with the films' crystallographic transformation. The predominant p-type conductivity and optimum annealing time for higher mobility have been confirmed from the Hall measurement. Films' optoelectrical properties were implemented in the complete perovskite solar cell for numerical analysis. The simulation results show that a 40 min annealed CuxO film yields the highest efficiency of 22.56% with a maximum open-circuit voltage of 1.06 V. [ABSTRACT FROM AUTHOR]

Planar perovskite solar cells were fabricated on F-doped SnO2 (FTO) coated glass substrates, with 4,4'-((1E,1'E)-((1,2,4-thiadiazole-3,5-diyl)bis(azaneylylidene))bis(methaneylylidene))bis(N,N-di-p-tolylaniline) (bTAThDaz) as hole transport material. This imine was synthesized in one step reaction, starting from commercially available and relatively inexpensive reagents. Electrochemical, optical, electrical, thermal and structural studies including thermal images and current-voltage measurements of the full solar cell devices characterize the imine in details. HOMO-LUMO of bTAThDaz were investigated by cyclic voltammetry (CV) and energy-resolved electrochemical impedance spectroscopy (ER-EIS) and were found at −5.19 eV and −2.52 eV (CV) and at −5.5 eV and −2.3 eV (ER-EIS). The imine exhibited 5% weight loss at 156 °C. The electrical behavior and photovoltaic performance of the perovskite solar cell was examined for FTO/TiO2/perovskite/bTAThDaz/Ag device architecture. Constructed devices exhibited good time and air stability together with quite small effect of hysteresis. The observed solar conversion efficiency was 14.4%. [ABSTRACT FROM AUTHOR]