Low-temperature solution-combustion-processed Zn-Doped Nb2O5 as an electron transport layer for efficient and stable perovskite solar cells

Abstract

Niobium oxide (Nb2O5) has been demonstrated as an ideal electron transport layer (ETL) material for perovskite solar cells (PSCs) due to its excellent optical transmittance and high carrier mobility. Herein, a low-temperature (200 °C) solution-combustion method is adopted to prepare the Nb2O5 film used as an ETL in PSCs. Under optimized conditions, PSC with the Nb2O5 ETL obtains a power conversion efficiency (PCE) of 16.40%. Moreover, we find that Zn-doping of Nb2O5 can further improve the efficiency of the device. As a matter of fact, the results show that a champion PCE of 17.70% can be achieved for the PSC with a 5 mol% Zn-doped Nb2O5 ETL. Significantly, both Nb2O5- and Zn-doped Nb2O5-based devices exhibit obviously better stability than the traditional high-temperature-sintered (~500 °C) mesoporous TiO2-based devices, maintaining 80% of their initial PCE after storage in air for 20 days. In contrast, the PCE of the device with a TiO2 ETL quickly drops to 30% of its initial value after 13 days under the same storage condition. Consequently, this work suggests that using Zn-doped Nb2O5 ETL prepared by the low-temperature solution-combustion method is promising towards efficient and stable perovskite solar cells.