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Pb‐free perovskites are novel compounds that are currently being studied, essentially for their photovoltaic applications. In this article, the hybrid organic–inorganic perovskite for photovoltaic applications is studied. In fact, the structural and electronic properties of the perovskite FABI3 (B = Sn, Ge, or Pb and FA = formamidinium: CH(NH2)2) applying the density functional theory method executed in the Quantum Espresso framework are studied and discussed. The band structures of these perovskites have been presented; it is shown that these perovskites have a semiconductor nature, with a bandgap value of 1.36 eV for FASnI3, 1.72 eV for FAGeI3, and 1.61 eV for FAPbI3. Also, the density of states and partial density of states have been presented and discussed for each of these materials. Indeed, the structural properties of these perovskites are investigated and demonstrated that the optimized value of the lattice parameter is 6.35 Å for the FASnI3, while for the FAGeI3, this value is 6.3 Å and 6.5 Å for FAPbI3. Moreover, the impact of the lattice parameter on the bandgap value of FABI3 (B = Sn, Ge, or Pb) has been investigated, and it has been demonstrated that as the lattice parameter increases, the bandgap increases. The results of this work can be utilized as a guideline for the development of new efficient, lead‐free perovskite devices, including tandem solar cells. [ABSTRACT FROM AUTHOR]

Following the 2nd release of the "Emerging PV reports," the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer‐reviewed articles in academic journals since August 2021. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open‐circuit voltage, short‐circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application, and are put into perspective using, e.g., the detailed balance efficiency limit. The 3rd installment of the "Emerging PV reports" extends the scope toward triple junction solar cells. [ABSTRACT FROM AUTHOR]

Following the 1st release of the "Emerging photovoltaic (PV) reports", the best achievements in the performance of emerging photovoltaic devices in diverse emerging photovoltaic research subjects are summarized, as reported in peer‐reviewed articles in academic journals since August 2020. Updated graphs, tables, and analyses are provided with several performance parameters, e.g., power conversion efficiency, open‐circuit voltage, short‐circuit current density, fill factor, light utilization efficiency, and stability test energy yield. These parameters are presented as a function of the photovoltaic bandgap energy and the average visible transmittance for each technology and application and are put into perspective using, e.g., the detailed balance efficiency limit. The 2nd instalment of the "Emerging PV reports" extends the scope toward tandem solar cells and presents the current state‐of‐the‐art in tandem solar cell performance for various material combinations. [ABSTRACT FROM AUTHOR]

The external quantum efficiency (EQE), also known as incident‐photon‐to‐collected‐electron spectra are typically used to access the energy dependent photocurrent losses for photovoltaic devices. The integral over the EQE spectrum results in the theoretical short‐circuit current under a given incident illumination spectrum. Additionally, one can also estimate the photovoltaic bandgap energy (Eg) from the inflection point in the absorption threshold region. The latter has recently been implemented in the "Emerging PV reports," where the highest power conversion efficiencies are listed for different application categories, as a function of Eg. Furthermore, the device performance is put into perspective thereby relating it to the corresponding theoretical limit in the Shockley–Queisser (SQ) model. Here, the evaluation of the EQE spectrum through the sigmoid function is discussed and proven to effectively report the Eg value and the sigmoid wavelength range λs, which quantifies the steepness of the absorption onset. It is also shown how EQE spectra with large λs indicate significant photovoltage losses and present the corresponding implications on the photocurrent SQ model. Similarly, the difference between the photovoltaic and optical bandgap is analyzed in terms of λs. [ABSTRACT FROM AUTHOR]

Emerging photovoltaics (PVs) focus on a variety of applications complementing large scale electricity generation. Organic, dye‐sensitized, and some perovskite solar cells are considered in building integration, greenhouses, wearable, and indoor applications, thereby motivating research on flexible, transparent, semitransparent, and multi‐junction PVs. Nevertheless, it can be very time consuming to find or develop an up‐to‐date overview of the state‐of‐the‐art performance for these systems and applications. Two important resources for recording research cells efficiencies are the National Renewable Energy Laboratory chart and the efficiency tables compiled biannually by Martin Green and colleagues. Both publications provide an effective coverage over the established technologies, bridging research and industry. An alternative approach is proposed here summarizing the best reports in the diverse research subjects for emerging PVs. Best performance parameters are provided as a function of the photovoltaic bandgap energy for each technology and application, and are put into perspective using, e.g., the Shockley–Queisser limit. In all cases, the reported data correspond to published and/or properly described certified results, with enough details provided for prospective data reproduction. Additionally, the stability test energy yield is included as an analysis parameter among state‐of‐the‐art emerging PVs. [ABSTRACT FROM AUTHOR]

The Tantalum oxide material (Ta2O5) as tunnel oxide in comparison with the Silicon dioxide (SiO2) Tunnel oxide is proposed. The lower bandgap and high refractive index of Ta2O5 has several advantages over SiO2. The Ta2O5 is used as Anti-Reflecting coating earlier, but also has capability to behave as the tunneling oxide. In the ultrathin region, the Tantalum oxide (Ta2O5) potentially produces extremely high tunneling and high electric field. The greater electrical intensity increases both the transportation of carrier and passivation quality of designed c-Si structure. The carrier selectivity is also increased due to very high capacitive nature. The performance measurement is done in ASTM certified AM1.5G environment using Silvaco ATLAS 2D TCAD tool. The comparison has been made between Ta2O5 and SiO2, to show the advantage of Ta2O5 over SiO2. The lower bandgap of 4.8eV and higher affinity of 3.19 of Ta2O5 as compared to SiO2 proves to be better material as tunneling oxide. The bandgap and electric field region of both the materials have been studied. In first approach to use Ta2O5 as tunneling oxide, the power conversion 28.42% is obtained for 0.1nm thickness of the Ta2O5. External and internal quantum efficiencies are well above 80% and 90% respectively. The characteristics of the Ta2O5 tunneling based solar cell are compared with the previous reported solar cell. [ABSTRACT FROM AUTHOR]

Adding dilute concentrations of nitrogen (N) or bismuth (Bi) into conventional III–V semiconductor alloys causes a large bowing of the bandgap energy due to the modification of the electronic band structure. This behaviour has attracted significant interest due to the resulting optical and electronic properties. Firstly, the authors present theoretical band structure models for GaAs‐based dilute nitride, dilute bismide and dilute bismide‐nitride alloys and then use them within current continuity equations to show the photovoltaic behaviour. To describe the band structures of these highly mismatched III–V semiconductor alloys, the authors introduce a 10‐, 12‐ and 14‐band k⋅p Hamiltonian for dilute nitride, dilute bismide and dilute bismide‐nitride semiconductors, respectively. The authors then use this approach to analyse GaBiAs multi‐quantum well p‐i‐n structures for photovoltaic performance. Through theoretical analysis the authors can: (i) elucidate important trends in the properties and photovoltaic performance of GaBiAs QW structures and (ii) comment generally on the suitability of GaBiAs alloys and heterostructures for applications in multi‐junction solar cells. In particular, the authors identify and quantify the limitations associated with current GaBiAs solar cells, and describe the improvements in performance that can be expected pending further development of this emerging class of devices. [ABSTRACT FROM AUTHOR]

Although the power conversion efficiency (PCE) of colloidal quantum dot solar cells (CQDSCs) has increased sharply, researchers are struggling with the lack of comprehensive device efficiency optimization strategies, which retards significant progress in CQDSC improvement. This paper addresses this critical issue through analyzing the impact of colloidal quantum dot (CQD) carrier hopping mobility, bandgap energy, illumination intensity, and electrode/CQD interface on device performance to develop a guiding criterion for CQDSC PCE optimization. This general strategy has been used for the successful fabrication of high-efficiency CQDSCs yielding certified PCEs as high as 11.28 %. A major experimental finding of this work is that the widely used constant photocurrent density ( J ph) assumption is invalid as J ph is external-voltage dependent due to the low carrier hopping mobility. Furthermore, the theoretical model developed herein predicts the nonmonotonic dependence of CQDSC PCE on carrier hopping mobility and bandgap energy, which were also demonstrated with the high-efficiency CQDSCs. These results constitute a revision basis of the widespread belief that higher mobility and lower bandgap energy correspond to a higher CQDSC efficiency. Furthermore, electrode/CQD interface-dependent surface recombination velocities were investigated in the framework of our abovementioned theoretical model using lock-in carrierography, a contactless, large-area frequency-domain photocarrier diffusion-wave imaging methodology that elucidated the carrier collection process at the electrodes through open-circuit voltage distribution imaging. Lock-in carrierography eliminates the limitations of today's widely used small-spot (<0.1 cm2) testing methods which, however, raise questionable overall solar cell performance and stability estimations. [ABSTRACT FROM AUTHOR]

In the research of non-toxic perovskite for photovoltaic applications, the chalcogen impurities (S, Se, Te) effects on electronic, optical, and thermoelectric properties of AgTaO 3 were carried out using the density functional theory. The calculated results revealed that the bandgap is inversely proportional to the increase of the chalcogens' concentrations due to the improvement of the charge carrier's mobility. Therefore, the absorption and optical conductivity edges are extended into the visible spectrum, especially for A g T a O 2.9584 T e 0.0416 perovskite due to its suitable bandgap value. Additionally, Te-doped AgTaO 3 has the highest Seebeck coefficient values while the electrical and thermal conductivities values increased with increasing temperature for all studied compounds. Our findings suggest that all compounds are a potential candidate in photovoltaic device applications. • The effects of chalcogen impurities (S, Se, Te) on electronic, optical, and thermoelectric properties of AgTaO 3 are studied. • The results revealed that the doping with chalcogen elements resulted in a drastic reduction of the high electronic bandgap. • The absorption and optical conductivity edges are extended into the visible spectrum. • Te-doped AgTaO 3 has the highest Seebeck coefficient values while the electrical and thermal conductivities values. [ABSTRACT FROM AUTHOR]

Highlights: [•] Photovoltaic conversion of sunlight is promising as a carbon-free-energy-source. [•] An optimized multi-junction photovoltaic cell was attempted and reached. [•] 58% efficiency can be reached with five junctions. [ABSTRACT FROM AUTHOR]

A single crystal of the non-centrosymmetric low-temperature modification of Tl 2 CdSnSe 4 (space group I 4 ‾ 2m) was grown, for the first time, and its electronic and optical properties were studied from both experimental and theoretical viewpoints. The Tl 2 CdSnSe 4 crystal was grown from the solution-melt by vertical Bridgman-Stockbarger method. Centimeter dimensions of the crystal allow its application in practice. The bandgap energy, E g = 1.32 eV, estimated from the optical absorption coefficient agrees well with the value of E g = 1.29 eV calculated from the photosensitivity measurements. X-ray photoelectron spectroscopy (XPS) was used to investigate the electronic structure and charge states of atoms composing the crystal under consideration. To detect the best agreement of the curve of total densities of states (DOS) with the experimental XPS spectrum of valence electrons of Tl 2 CdSnSe 4 , we performed theoretical calculations within a density functional theory (DFT) framework treating different models for exchange correlation (XC) potential. Our findings yield that the best agreement of the experimental and theoretical distributions of the valence electronic states is derived when using in the computation procedure for XC potential the modified Becke-Johnson potential in the form of Tran-Blaha (TB-mBJ), which involves also the Hubbard parameter U for strongly correlated d electrons and spin-orbit coupling (SOC) effect (TB-mBJ + U + SOC model). Based on this approach, we calculated partial densities of states, energy band dispersion, and main optical constants of Tl 2 CdSnSe 4. Importantly, the TB-mBJ + U + SOC model reveals the E g value which is close to those determined experimentally; therefore, scissors correction adjustment is not required when performing DFT calculations of the optical constants in such a case. The present experimental XPS measurements of the treated with middle-energy Ar+-ions Tl 2 CdSnSe 4 crystal surface and the theoretical DFT calculations data indicate, in spite of its rather hazardous chemical elements, thallium and cadmium, the crystal surface is rather stable and, coupled with suitable energy band gap, makes quaternary selenide under discussion a very promising material for using in thin film solar cells and optoelectronics as well as in highly efficient photocatalytic devices. Image 1 • For the first time, a crystal of non-centrosymmetric Tl 2 CdSnSe 4 (space group I 4 ‾ 2m) was grown. • Electronic structure of Tl 2 CdSnSe 4 crystal was studied by XPS. • Total and partial densities of states are calculated withinDFT framework. • Calculations within TB-mBJ + SOC + U model are in agreement with XPS measurements. • Principal optical constants of Tl 2 CdSnSe 4 are explored in detail. [ABSTRACT FROM AUTHOR]

Photoanode materials with optimized particle sizes, excellent surface area and dye loading capability are preferred in good-performance dye sensitized solar cells. Herein, we report on an efficient dye-sensitized mesoporous photoanode of Ti doped zinc oxide (Ti-ZnO) through a facile hydrothermal method. The crystallinity, morphology, surface area, optical and electrochemical properties of the Ti-ZnO were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction. It was observed that Ti-ZnO nanoparticles with a high surface area of 131.85 m2 g−1 and a controlled band gap, exhibited considerably increased light harvesting efficiency, dye loading capability, and achieved comparable solar cell performance at a typical nanocrystalline ZnO photoanode. [ABSTRACT FROM AUTHOR]