A Solution-Processed Spinel CuCo₂O₄ as an Effective Hole Transport Layer for Efficient Perovskite Solar Cells with Negligible Hysteresis

Optimal optoelectronic properties of interfacial layers in perovskite solar cells are essential for achieving high power conversion efficiency. We herein demonstrated a solution-processed spinel CuCo₂O₄ as a hole transport layer to use in high-performance perovskite solar cells. The solution-processed CuCo₂O₄ possessed high electrical conductivity, high optical transparency in UV-vis-NIR, well-matched energy levels to perovskite, and efficient hole transport capability to the perovskite layer. The optoelectronic properties of CuCo₂O₄ were finely controlled by optimizing the annealing temperature, leading to a 14.12% power conversion efficiency in planar perovskite solar cells. Another impressive advantage for the CuCo₂O₄-based hole transport layer is a negligible hysteresis of the device at very low scan rate, which brought about highly stable and reliable photovoltaic performance. All of the results studied in this work suggest a bright future for solution-processed CuCo₂O₄ as a novel hole transport layer in perovskite solar cells with high efficiency and good stability.