Hybrid interfacial ETL engineering using PCBM-SnS₂ for High-Performance p-i-n structured planar perovskite solar cells

Fullerene derivatives, such as PCBM i.e. [6,6]-phenyl C61 butyric acid methyl ester, are actively used as electron-transport layers (ETL) in inverted perovskite solar cells (PSC). However, limitations, such as low electron transportation, large electron trap region, poor film formation, and profuse non-radiative recombination, at the perovskite/PCBM interface result in relatively low performance in inverted PSC. Herein, a significant strategy to overcome these challenges was envisaged via using tin disulphide (SnS₂) combined with PCBM, forming a uniform mixture of PCBM-SnS₂ with high electron transportation and favorable energy levels. In addition, the greater relative permittivity of SnS₂ permits shrinkage in critical electron captured radius from 0.62 nm to 0.22 nm, thus reducing leakage current and non-radiative recombination at the perovskite/PCBM-SnS₂ interface. The efficiency of PCBM-SnS₂ ETL based inverted PSC reached up to approximately 20% having a high 82% fill factor along with improved internal and external quantum efficiencies. The PCBM-SnS₂ ETL reduced the charge transportation resistance and increased recombination resistance. The device stability was improved due to increased hydrophobicity and electrical compactness of the PCBM-SnS₂. Hence, the synergetic effect of PCBM-SnS₂ as an efficient ETL has great potential in improving the performance of planar inverted PSC.