Efficient and stable planar perovskite solar cells using co-doped tin oxide as the electron transport layer

The electron transport layer (ETL) plays a pivotal role in the photovoltaic performance and overall stability of the perovskite solar cell. In the present study, aluminium and lanthanum trivalent metals are co-doped into the low temperature solution processed SnO₂ electron transport layer (ETL). Unlike the pristine and individually doped SnO₂ ETL, the AlLa–SnO₂ ETL exhibits superior transmittance, well-aligned band energy levels and efficient charge transportation. Contrary to the pristine SnO₂ device with power conversion efficiency (PCE) of 17.21%, the 0.5% of Al and 0.5% of La doped SnO₂ (AlLa–SnO₂) ETL device display paramount PCE of 19.13%. Furthermore, recombination resistance and consistency show significant improvements, enabling excellent stability in the AlLa–SnO₂ ETL device to which 90% of its initial PCE is retained despite storage at the relative humidity of 40% for 30 days without encapsulation. Henceforth, this study demonstrates the suitability of co-doping as a promising approach to fabricate exceptional ETLs for efficient, stable and reproducible planar perovskite solar devices.