2D/3D heterojunction engineering at the grain boundaries towards high-performance inverted MA-free perovskite solar cells

The construction of multidimensional (2D/3D) heterojunction perovskites as light-harvesting layers has emerged as one of the most dependable strategies for stabilizing perovskite solar cells (PSCs) without compromising their photovoltaic performance, amidst the plethora of stability-enhancing techniques that have been reported. Herein, we have identified a 2D/3D heterojunction perovskite of FAPbI3, which is based on a small molecular Pivalimidamide hydrochloride and has demonstrated the ability to effectively enhance both the efficiency and stability of PSCs. Device characterizations have revealed that the 2D/3D structure modification improves the fluorescence lifetime, decrease grain boundaries (GBs) defects and ultimately results in achieving efficiencies of 22.06% based on CsFAPbI3. The introduction of the 2D layer improves film uniformity and inhibit phase separation as verified by photoluminescence measurement. Unencapsulated devices were stored at room temperature under N2 conditions for 1000 h, with 92% of the initial efficiency. It remains 80% of its initial efficiency after continuous operation under illumination at the maximum power point and at a temperature of 40 °C for over 440 h.