Modeling Highly Efficient Homojunction Perovskite Solar Cells With Graphene-TiO2 Nanocomposite as the Electron Transport Layer

Perovskite-based solar cells have observed tremendous growth in the last decade aiming at developing renewable energy sources. The enhancement of the power conversion efficiency (PCE), sustainability, and easing of the fabrication are the main driving forces of the ongoing research activity. In this context, graphene is particularly promising since it not only provides better charge collection but also helps to improve the sustainability and low-temperature fabrication of the perovskite cell. Here, a homojunction MaPbI
₃
perovskite solar cell with graphene-TiO
₂
nano-composite as the electron transport layer (ETL) has been numerically investigated. The effect of doping concentration on the p and n-doped section in the homojunction-MaPbI
₃
has been studied, showing that 10
¹⁷
and 10
¹⁶
cm
⁻³
doping on the p and n section of MaPbI
₃
, respectively, provide the best band alignment with the ETL layer. The optimum thickness ratio of two doped sections (p:n) is found to be 60:40 in %. Moreover, the presence of graphene in the TiO
₂
layer improves PCE thanks to enhanced fill factor and saturated current density. A combined effect of all these results in a PCE of 22.71% with a 100 nm thick ETL layer having an optimum graphene concentration of around 1%.