Design and simulation of efficient tin based perovskite solar cells through optimization of selective layers: Theoretical insights

Abstract

Within a decade, Perovskite solar cells (PSCs) have attained an efficiency of 25.8%. PSCs lack commercialization due to two main factors: (i) poor device stability (ii) toxicity. The tin (Sn) is a possible candidate to substitute toxic lead (Pb) in traditional PSCs; however, the performance of Sn-based PSCs is 13%, much lower than Pb-based PSCs due to several aspects. In this work, we have used drift-diffusion simulation to propose a pathway to improve the performance of lead-free PSCs using MASnI3 as a light harvester. The conventional charge selective layer, such as TiO2, requires high-temperature processing, which also is a major concern. As reported earlier, traditional transport layers contribute actively to the degradation of PSCs, affecting their stability. Therefore, we have used ZnO nanoparticles (NP) as electron transport material (ETM), and conducted an analysis using various organic and inorganic hole transport materials (HTMs) with spike and cliff structures. The impact of HTM thickness on the performance parameters of MASnI3 based PSCs with constant and variable charge acceptor concentrations was investigated. This work indicates that organic HTMs exhibit more thickness-dependent behavior than inorganic HTM for MASnI3 based PSCs. Furthermore, the suitable valence band offset (VBO) and barrier height at Perovskite/HTM and HTM/Back contact interfaces were studied for efficient energy level mismatch with absorber layer to boost the performance of MASnI3 based PSCs. The concept of selecting back contact for Sn-based PSCs using different HTMs was analyzed. The influence of temperature variation on the performance of PSCs using different HTM was analyzed. The hybrid configuration devices face the issue of interfacial recombination; thus, the impact of defect density at the HTM/MASnI3 interface on the performance of PSCs with various HTMs was investigated. Lastly, MASnI3 based PSC showed a power conversion efficiency (PCE) of 23.51% using the unmodified CuSCN based HTM and, CuI can also deliver an efficiency of 23.31% employed modified valence band energy level.