High-performance and stable inverted perovskite solar cells using low-temperature solution-processed CuNbOx hole transport layer

Abstract

For a typical perovskite solar cell (PSC), the hole transport layer (HTL) plays a vital role in determining device performance and stability. Herein, for the first time, we demonstrate that a low-temperature solution-processed copper-niobium oxide (CuNbOx) thin film, consisting of CuNbO3 and CuNb2O6 phases, can serve as an efficient HTL to develop PSCs with high-performance and long-term stability simultaneously. The CuNbOx thin film possesses high optical transparency in visible light, well-matched energy levels with perovskite, and excellent hole extraction capability from the perovskite layer. By optimizing the precursor concentration, the CuNbOx-based device reaches the best power conversion efficiency (PCE) of 16.01% with negligible hysteresis. In comparison, the control device based on the extensively studied PEDOT:PSS HTL shows an obviously lower PCE of 10.13%. Besides exhibiting significant improvement in photovoltaic performance, our CuNbOx-based device also shows much enhanced long-term stability than the control device. After 1000 h of storage in air without encapsulation, the CuNbOx-based PSCs maintains ~78% of their initial efficiency, whereas the PCE of PEDOT:PSS-based PSCs drops to ~44% of the initial value. Overall, this study suggests that the utilization of the inorganic CuNbOx thin film as the HTL provides a novel route for fabricating low-cost, high-performance, and stable PSCs.