Semiconductor heterojunctions coated with reduced graphite oxide as electron transfer materials for high-performance perovskite solar cells

Abstract

Exploring and insight into the relationship between the microstructure, light absorption performance, and carrier transport of perovskite light absorption layer materials and carrier transport layer materials is crucial for obtaining efficient and stable perovskite solar cells. We adopted a simple strategy to prepare a composite material known as reduced graphene oxide wrapped mesoporous hierarchical TiO2–CdS semiconductor heterojunctions (TiO2–CdS-RGO) as the electron transport layer in formamidine lead iodide perovskite solar cells. Compared with single TiO2 and binary composite, this composite material exhibits enhanced photoluminescence quenching, reduced photo generated carrier recombination rate, and improved electron transfer capability. Photovoltaic devices based on TiO2–CdS-RGO composite material showed a 14.5 % increase in short-circuit current density (JSC) and a 36.3 % increase in photoelectric conversion efficiency (PCE) compared to those with only TiO2. The improved optoelectronic properties observed with the TiO2–CdS-RGO as electron transfer layers can be attributed to several factors. On the one hand, mesoporous TiO2 with a high specific surface area is beneficial for perovskite infiltration and enhances electron transfer rate. On the other hand, the well-matching energy level structure among the three components aids in electrons extraction and reduces the recombination rate of photo generated charge carriers; In addition, RGO nanosheets with high conductivity serve as an efficient electron transfer network, providing a rapid charge transfer pathways, which is crucial for enhancing the photoelectric conversion performance of perovskite solar cells.