Effect of tantalum doping on SnO2 electron transport layer via low temperature process for perovskite solar cells

The electron transport layer (ETL) plays an important role in determining the device performance of perovskite solar cells (PSCs). Recently, SnO2 has been used extensively as an ETL due to its many outstanding optoelectronic properties. Herein, we develop Ta doped SnO2 (Ta-SnO2) as an ETL grown by chemical bath deposition, allowing the fabrication of low-temperature PSCs. In contrast to pristine SnO2, the I-V curve and transmittance spectra show a significant conductivity improvement of Ta-SnO2 without declining the light transmittance property. Meanwhile, Ta-doping could accelerate the electron transfer and decrease the recombination probability at the SnO2/perovskite interface, as well as passivate the electron traps, leading to the improvement in the PSC performance. Through a series of optimization methods, the champion device shows a power conversion efficiency of 20.80%, with an open-circuit voltage of 1.161 V, a short-circuit current density of 22.79 mA/cm(2), and a fill factor of 0.786. SnO2 with a suitable Ta content is a promising candidate as an ETL for fabricating high-efficiency PSCs via the low-temperature process.