Improved photovoltage of printable perovskite solar cells via Nb⁵⁺ doped SnO₂ compact layer

The state-of-the-art perovskite solar cells (PSCs) with SnO₂ electron transporting material (ETL) layer displays the probability of conquering the low electron mobility and serious leakage current loss of the TiO₂ ETL layer in photoelectronic devices. The rapid development of SnO₂ ETL layer has brought perovskite efficiencies >20%. However, high density of defect states and voltage loss of high temperature SnO₂ are still latent impediment for the long-term stability and hysteresis effect of photovoltaics. Herein, Nb⁵⁺ doped SnO₂ with deeper energy level is utilized as a compact ETL for printable mesoscopic PSCs. It promotes carrier concentration increase caused by n-type doping, assists Fermi energy level and conduction band minimum to move the deeper energy level, and significantly reduces interface carrier recombination, thus increasing the photovoltage of the device. As a result, the use of Nb⁵⁺ doped SnO₂ brings high photovoltage of 0.92 V, which is 40 mV higher than that of 0.88 V for device based on SnO₂ compact layer. The resulting PSCs displays outstanding efficiency of 13.53%, which contains an ∼10% improvements compared to those without Nb⁵⁺ doping. Our study emphasizes the significance of element doping for compact layer and lays the groundwork for high efficiency PSCs.