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Using a one-dimensional solar cell capacitance simulator (SCAPS-1D), the initial simulation study is carried out by using inorganic Pb-free RbGeI3-based perovskite layer along with 2,2′,7,7′- tetrakis [N, N-di4-methoxyphenylamino]-9,9′-spirobifluorene (Spiro-OMeTAD) as a hole transport layer (HTL) and titanium dioxide (TiO2) as an electron transport layer (ETL), which shows a device efficiency of 13.11%. In addition, we investigated the impact of the conduction band offset (CBO) between the ETL and absorber layer, and the valence band offset (VBO) between the absorber and HTL. Band offsets play a critical role in carrier recombination at the interfaces, which determines the open-circuit voltage (Voc). Our study found that extremely negative and positive band offsets lead to reduced PV performance. The optimum position of CBO with respect to the perovskite layer is found to be − 0.2 to − 0.1 eV, while the optimum position of VBO is found to be − 0.1 to 0.0 eV. When ETL is replaced by ZnSe and HTL by CuSCN, the device shows an improved power conversion efficiency (PCE) of 15.82%, as predicted by band offset engineering. The effect of thickness and defect density of perovskite layer, back contact work function, series resistance, shunt resistance, and temperature on the performance of perovskite solar cell (PSC) has been analyzed. The optimized device exhibited a PCE of 17.93%, fill factor (FF) of 74.96%. Thus, the proposed simulation study promotes RbGeI3 as a promising candidate for the absorbing layer and provides significant insight that will help to find out the suitable ETL and HTL combination. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have gained popularity in recent times due to their high-power conversion efficiency (PCE) and cost-effective manufacturing. Heterojunction devices are emerging as an interesting topic for researchers. In this study, a comparison is made between the experimental performance and their numerical simulations using the solar cell capacitance simulator (SCAPS-1D) software of CsPbI3/CsPbBr3 perovskite bilayer and CsPbI3 single-layer perovskite solar cell. It is evident from the experimental results that the incorporation of CsPbBr3 layer enhances the PCE from 4.92 to 9.9% under solar illumination. Further, an ideally optimized device was made using SCAPS-1D by varying the thickness, defect density, back metal contact and temperature. The influence of series and shunt resistances (Rseries and Rshunt) was theoretically investigated and discussed using the SCAPS-1D program to model the electrical characteristics of the cell as a function of active layer composition. Without these parasitic resistances, the results of the ideal device do not resemble the experimentally calculated values. By feeding the experimentally calculated Rseries and Rshunt values to SCAPS-1D, we can analyse the primary constraints of the device's current voltage characteristics. Ultimately, it is established that the heterojunction device can help in enhancing the performance of PSCs. [ABSTRACT FROM AUTHOR]

Lead-based perovskite solar cells have experienced tremendous growth and achieved an outstanding power conversion efficiency (PCE) of 27.4% during the last decade. However, lead poisoning has remained a matter of concern for commercialization. Therefore, researchers are looking for alternative perovskite materials free from lead. Cesium-based perovskite material CsGeIXBr3−X may be a promising alternative due to its favorable optical conductivity and light absorption coefficient. To understand the atomic level calculation of perovskite solar cells (PSCs), a detailed model of interaction between the electrons and the interface is strongly anticipated. The optoelectronic property of the perovskite absorber layer has the most significant impact on device performance. Using Density functional theory (DFT), we can precisely predict the behavior of charge transport layers, including the active perovskite layer. In this work, we have done first-principles calculations based on DFT to analyze the electronic and optical properties of lead-free full inorganic CsGeIXBr3−X perovskite compounds. In addition, we incorporate DFT-extracted values of the electronic band gap, the effective density of states, and the optical absorption spectrum in the Solar cell capacitance simulator (SCAPS-1D) program to understand the device performance with the variation of thickness and total defect density of the perovskite layer. We obtained the value of the energy bandgap as 1.363 eV for CsGeI3, 1.5795 eV for CsGeI2Br, 1.7493 eV for CsGeIBr2 and 1.885 eV for CsGeBr3. The CsGeI3-based device performs best and achieves maximum power conversion efficiency (PCE) of 27.63%. It was observed that while increasing the doping concentration of Br in CsGeIXBr3−X perovskites, the bond length decreases, and consequently, the bandgap increases. Also, as the doping concentration increases, a substantial blue shift was observed in the calculated optical conductivity and absorption spectra. [ABSTRACT FROM AUTHOR]