Enhanced energy level alignment and hole extraction of carbon electrode for air-stable hole-transporting material-free CsPbBr3 perovskite solar cells

Abstract Carbon-based hole-transporting material (HTM)-free CsPbBr3 perovskite solar cells (PSCs) provide new opportunities for promoting the commercial application of PSCs because of the low cost, simple preparation process and excellent stability under various extreme conditions. One of the remaining problems for inorganic CsPbBr3 PSCs is the low power conversion efficiency (PCE) due to the large energy level difference and inefficient hole extraction at CsPbBr3/carbon interface. Herein, polyaniline/graphite (PANi/G) composites are incorporated into carbon electrode to tailor work function and to improve hole-selectivity of back electrode for enhanced energy level alignment and interfacial hole extraction, leading to a remarkably reduced energy loss and charge recombination. The HTM-free CsPbBr3 PSC based on carbon-PANi/G electrode achieves a PCE of 8.87%, which is increased by 43.8% in comparison with 6.17% for the control device. Moreover, the unencapsulated device shows excellent long-term moisture tolerance with the initial PCE maintaining 93.5% even exposure to air atmosphere with 80% RH at 25 °C over 50 days. The successful improvement of energy level alignment and charge extraction in device by directly incorporating PANi/G composites into carbon electrode offers a promising strategy in developing low-cost and efficient HTM-free PSCs.