Hole transporting layer optimization for an efficient lead-free double perovskite solar cell by numerical simulation

The double perovskite structured Cs2AgBiBr6 has got great attention as a light harvester in perovskite solar cells (PSCs) at present. In this work, the device configuration FTO/SnO2/Cs2AgBiBr6/P3HT/Au was analyzed using solar cell capacitance simulation software (SCAPS-1D) initially and a low PCE of 1.81% was found due to the non-suitable band alignment of P3HT with perovskite and its lower carrier mobility. Thus, to improve the device performance P3HT was replaced with various hole transporting materials (HTMs) like CuSbS2, MoO3, Cu2O, CuSCN, NiO, PEDOT:PSS and Spiro-OMeTAD and the performance of the device was analyzed. The three devices CuSbS2, MoO3 and Cu2O were found to be the three most efficient devices respectively. Further the thickness of absorber and HTL was optimized for these three devices. Also the impact of defect density in absorber was studied by varying its value from 1 × 1013 cm−3 to 1 × 1019 cm−3 for the most efficient device (CuSbS2 as HTL). All these analysis revealed that for the highest performing and practical device consisted of 200 nm CuSbS2 as HTL and 400 nm of absorber with defect density 1 × 1015 cm−3 conferred superior solar cell output electrical parameters than that of all other devices (based on different HTLs) which are VOC = 0.99 V, JSC = 14.51 mA/cm2, FF = 68.88% and PCE = 9.98%.