Optimization of spiro–OMeTAD as the buffer layer for CH3NH3PbI3 perovskite solar cells using SCAPS

Spiro-OMeTAD, a hole transport material (HTM), has garnered significant attention in perovskite solar cell (PSC) research for enhancing the efficiency and stability of methylammonium lead iodide (CH₃NH₃PbI₃) devices. However, perovskite lead contains material that faces challenges such as thermal instability, lead toxicity, limited power conversion efficiency, and obstacles to the commercialization of PSC devices. In this work, we numerically optimized an inverted device structure (Spiro-OMeTAD/methylammonium lead iodide/PCBM/ZnO/ITO) using the solar cell simulation tool via Solar Cell Capacitance Simulator (SCAPS). Here, the Spiro-OMeTAD material functions as the hole transport layer, while the PCBM and zinc oxide (ZnO) form the electron transport bilayer, with the Indium tin oxide (ITO) serving as the transparent conductive electrode. By carefully adjusting the thickness of buffer layer, charge carrier concentration, and parasitic resistance at varying operating temperatures, we achieved an optimized device that offers an efficiency (PCE) of 22.57 %, an open circuit voltage (V_OC) of 1.0838 V, a fill factor (FF) of 82.72 %, and a short circuit current density (J_SC) of 25.174476 mA/cm². These simulation results will assist in fabricating a perovskite device via Spiro-OMeTAD as the buffer layer to reduce the perovskite grain size. Metallic dopants promote the formation of oxidized radical cations. The buffer layer improves hole mobility, conductivity, and overall device stability by protecting against environmental degradation.