A cesium tin–germanium triiodide (CsSnGeI₃) perovskite-based solar cell (PSC) has been reported to achieve a high-power-conversion efficiency (PCE > 7%) and extreme air stability. A thorough understanding of the role of the interfaces in the perovskite solar cell, along with the optimization of different parameters, is still required for further improvement in PCE. In this study, lead-free CsSnGeI₃ PSC has been quantitatively analyzed using a solar cell capacitance simulator (SCAPS–1D). Five electron transport layers (ETL) were comparatively studied, while keeping other layers fixed. The use of SnO₂ as an ETL, which has the best band alignment with the perovskite layer, can increase the power conversion efficiency (PCE) of PSC by up to 30%. The defect density and thickness of the absorber layer has been thoroughly investigated. Results show that the device efficiency is highly governed by the defect density of the absorber layer. All the PSCs with a different ETL exhibit PCE exceeding 20% when the defect density of the absorber layer is in the range of 10¹⁴ cm⁻³–10¹⁶ cm⁻³, and degrade dramatically at higher values. With the optimized structure, the simulation found the highest PCE of CsSnGeI₃-based PSCs to be 30.98%, with an open circuit voltage (V_oc) of 1.22 V, short-circuit current density (J_sc) of 28.18 mA·cm⁻², and fill factor (FF) of 89.52%. Our unprecedented results clearly demonstrate that CsSnGeI₃-based PSC is an excellent candidate to become the most efficient single-junction solar cell technology soon.

In this investigation, we employ a numerical simulation approach to model a hydrogenated lead-free ${\mathrm{C}\mathrm{s}}_2\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{i}{\mathrm{B}\mathrm{r}}_6$ double perovskite solar cell with a p-i-n inverted structure, utilizing SCAPS-1D. Contrary to traditional lead-based perovskite solar cells, the ${\mathrm{C}\mathrm{s}}_2\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{i}{\mathrm{B}\mathrm{r}}_6$ double perovskite exhibits reduced toxicity and enhanced stability, boasting a maximum power conversion efficiency of $\mathrm{6.37\%}$. Given its potential for improved environmental compatibility, achieving higher efficiency is imperative for its practical implementation in solar cells. This paper offers a comprehensive quantitative analysis of the hydrogenated lead-free ${\mathrm{C}\mathrm{s}}_2\mathrm{A}\mathrm{g}\mathrm{B}\mathrm{i}{\mathrm{B}\mathrm{r}}_6$ double perovskite solar cell, aiming to optimize its structural parameters. Our exploration involves an in-depth investigation of various electron transport layer materials to augment efficiency. Variables that affect the photovoltaic efficiency of the perovskite solar cell are closely examined, including the absorber layer’s thickness and doping concentration, the hole transport layer, and the absorber defect density. We also investigate the impact of the doping concentration of the electron transport layer and the energy level alignment between the absorber and the interface on the photovoltaic output of the cell. After careful consideration, zinc oxide is chosen to serve as the electron transport layer. This optimized configuration surpasses the original structure by over four times, resulting in an impressive power conversion efficiency of $\mathrm{26.3\%}$, an open-circuit voltage of $1.278 \mathrm{V}$, a fill factor of $\mathrm{88.21\%}$, and a short-circuit current density of $23.30 \mathrm{m}\mathrm{A}.{\mathrm{c}\mathrm{m}}^{-2}$. This study highlights the critical role that numerical simulations play in improving the chances of commercializing Cs₂AgBiBr₆ double perovskite solar cells through increased structural optimization and efficiency.

Formamidinium tin iodide (FASnI₃)-based perovskite solar cells (PSCs) have achieved significant progress in the past several years. However, these devices still suffer from low power conversion efficiency ($\mathrm{PCE}=6\%$) and poor stability. Recently, Cesium (Cs)-doped Formamidinium tin iodide (${\mathrm{FA}}_{1-\mathrm{x}}{\mathrm{Cs}}_{\mathrm{x}}{\mathrm{SnI}}_3)$ showed enhanced air, thermal, and illumination stability of PSCs. Hence, in this work, ${\mathrm{FA}}_{1-\mathrm{x}}{\mathrm{Cs}}_{\mathrm{x}}{\mathrm{SnI}}_3$ PSCs have been rigorously studied and compared to pure FASnI₃ PSCs using a solar cell capacitance simulator (SCAPS) for the first time. The aim was to replace the conventional electron transport layer (ETL) TiO₂ that reduces PSC stability under solar irradiation. Therefore, ${\mathrm{FA}}_{1-\mathrm{x}}{\mathrm{Cs}}_{\mathrm{x}}{\mathrm{SnI}}_3$ PSCs with different Cs contents were analyzed with TiO₂ and stable ZnOS as the ETLs. Perovskite light absorber parameters including Cs content, defect density, doping concentration and thickness, and the defect density at the interface were tuned to optimize the photovoltaic performance of the PSCs. The simulation results showed that the device efficiency was strongly governed by the ETL material, Cs content in the perovskite and its defect density. All the simulated devices with ZnOS ETL exhibited $\mathrm{PCEs}$ exceeding $20\%$ when the defect density of the absorber layer was below ${10}^{15}{ \mathrm{cm}}^{-3}$, and deteriorated drastically at higher values. The optimized structure with ${\mathrm{FA}}_{75}{\mathrm{Cs}}_{25}{\mathrm{SnI}}_3$ as light absorber and ZnOS as ETL showed the highest $\mathrm{PCE}$ of $22\%$ with an open circuit voltage ${\mathrm{V}}_{\mathrm{oc}}$ of $0.89 \mathrm{V}$, short-circuit current density ${\mathrm{J}}_{\mathrm{sc}}$ of $31.4 \mathrm{mA}·{\mathrm{cm}}^{-2}$, and fill factor FF of $78.7\%$. Our results obtained from the first numerical simulation on Cs-doped FASnI₃ could greatly increase its potential for practical production.

A hybrid tin-based perovskite solar cell with p-i-n inverted structure is modeled and simulated using SCAPS. The inverted structure is composed of PEDOT:PSS (as hole transport layer—HTL)/GA${}_{0.2}$FA${}_{0.78}$SnI${}_3$-1% EDAI${}_2$ (as perovskite absorber layer)/C60-fullerene (as electron transport layer—ETL). Previous experimental studies showed that unlike conventional tin-based perovskite solar cells (PSC), the present hybrid tin-based PSC passes all harsh standard tests and generates a power conversion efficiency of only $8.3\%$. Despite the high stability that this material exhibits, emphasis on enhancing its power conversion efficiency (PCE) is crucial. To that end, various ETL and HTL materials have been rigorously investigated. The impact of energy level alignment between HTL/absorber and absorber/ETL interfaces have been elucidated. Moreover, the thickness and the doping concentration of all the previously mentioned layers have been varied to inspect their effect on the photovoltaic performance of the PSC. The optimized structure with CuI (copper iodide) as HTL and ZnOS (zinc oxysulphide) as ETL scored a PCE of $26\%$, which is more than three times greater than the efficiency of the initial structure. The current numerical simulation on GA${}_{0.2}$FA${}_{0.78}$SnI${}_3$-1% EDAI${}_2$ could greatly increase its chance for commercial development.