ABSTRACT The numerical simulation of lead-free perovskite cesium tin germanium halide (CsSnGeI3) and methyl ammonium germanium halide (CH3NH3GeI3) solar cells have been performed. It has been elucidated from the numerical simulation that as compare to the CH3NH3GeI3 based structure, CsSnGeI3 based structure depicts better photovoltaic performance under constant illumination condition. To enhance the device photovoltaic performance, the effects of different hole transport layer (HTL), defect density of the absorber layer, metal work function and the effect of temperature has been studied. In the present investigation, the effect of hole transport layers are analyzed by correlating the built-in voltage (Vbi) with the open circuit voltage (VOC). It has been obtained from the simulation results, that Vbi has a significant impact on VOC as the higher Vbi corresponds to the highest VOC. Moreover, the effect of defect density and metal work function is also studied. It is obtained from the simulation results, that the optimum defect density is found to be 1×1014 cm-3 and metal work function should be greater than or equal to 5 eV for both lead-free CH3NH3GeI3 and CsSnGeI3 based perovskite layer. Furthermore, to suggest possible lead-free alternatives for all-perovskite two-termainal multi-junction solar cell, an attempt is made to match the current of bottom perovskite layer i.e., CsSnGeI3 based perovskite layer to the top perovskite layer i.e., CH3NH3GeI3 based perovskite layer. To attain the current matching for bottom perovskite layer (CsSnGeI3 based perovskite layer) to top perovskite layer (CH3NH3GeI3 based perovskite layer), the bottom perovskite sub cell is fed with the filtered spectrum which is obtained by transmission from top electrode. After, the realization of current matching the short circuit current density of CsSnGeI3 based perovskite layer drops from 25.75 mA/cm2 to 15.32 mA/cm2 which is similar to CH3NH3GeI3 based perovskite absorber layer. In addition, it has been obtained from literature, that both the perovskite layers can be fabricated using solution–processing low-temperature technology. Hence, the numerical study suggests the possible alternatives for wide and narrow bandgap perovskite layers for the application to obtain highly efficient lead-free all-perovskite multi-junction solar cells.

中文翻译：

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高效无铅钙钛矿层在全钙钛矿多结太阳能电池应用中的数值模拟

摘要 对无铅钙钛矿铯锡锗卤化物（CsSnGeI3）和甲基铵卤化锗（CH3NH3GeI3）太阳能电池进行了数值模拟。数值模拟表明，与基于 CH3NH3GeI3 的结构相比，基于 CsSnGeI3 的结构在恒定光照条件下表现出更好的光伏性能。为了提高器件的光伏性能，研究了不同空穴传输层（HTL）、吸收层缺陷密度、金属功函数和温度的影响。在本研究中，通过将内置电压 (Vbi) 与开路电压 (VOC) 相关联来分析空穴传输层的影响。由仿真结果可知，Vbi 对 VOC 有显着影响，因为较高的 Vbi 对应于最高的 VOC。此外，还研究了缺陷密度和金属功函数的影响。仿真结果表明，无铅 CH3NH3GeI3 和 CsSnGeI3 钙钛矿层的最佳缺陷密度为 1×1014 cm-3，金属功函数应大于或等于 5 eV。此外，为了建议全钙钛矿双端多结太阳能电池可能的无铅替代品，尝试将底部钙钛矿层（即基于 CsSnGeI3 的钙钛矿层）与顶部钙钛矿层（即基于 CH3NH3GeI3 的钙钛矿层）的电流相匹配层。为了实现底部钙钛矿层（基于 CsSnGeI3 的钙钛矿层）与顶部钙钛矿层（基于 CH3NH3GeI3 的钙钛矿层）的电流匹配，底部钙钛矿子电池被馈入通过从顶部电极传输获得的过滤光谱。之后，实现与 CsSnGeI3 基钙钛矿层短路电流密度匹配的电流从 25.75 mA/cm2 下降到 15.32 mA/cm2，类似于 CH3NH3GeI3 基钙钛矿吸收层。此外，从文献中获悉，这两个钙钛矿层都可以使用溶液处理低温技术制造。因此，数值研究提出了宽禁带和窄禁带钙钛矿层的可能替代方案，用于获得高效无铅全钙钛矿多结太阳能电池的应用。实现与 CsSnGeI3 基钙钛矿层短路电流密度匹配的电流从 25.75 mA/cm2 下降到 15.32 mA/cm2，类似于 CH3NH3GeI3 基钙钛矿吸收层。此外，从文献中可以看出，两种钙钛矿层都可以使用溶液处理低温技术制造。因此，数值研究提出了宽禁带和窄禁带钙钛矿层的可能替代方案，用于获得高效无铅全钙钛矿多结太阳能电池的应用。实现与 CsSnGeI3 基钙钛矿层短路电流密度匹配的电流从 25.75 mA/cm2 下降到 15.32 mA/cm2，类似于 CH3NH3GeI3 基钙钛矿吸收层。此外，从文献中可以看出，两种钙钛矿层都可以使用溶液处理低温技术制造。因此，数值研究提出了宽禁带和窄禁带钙钛矿层的可能替代方案，用于获得高效无铅全钙钛矿多结太阳能电池的应用。两个钙钛矿层都可以使用溶液处理低温技术制造。因此，数值研究提出了宽禁带和窄禁带钙钛矿层的可能替代方案，用于获得高效无铅全钙钛矿多结太阳能电池的应用。两个钙钛矿层都可以使用溶液处理低温技术制造。因此，数值研究提出了宽禁带和窄禁带钙钛矿层的可能替代方案，用于获得高效无铅全钙钛矿多结太阳能电池的应用。