De-templated crystallization in 2D perovskites for enhanced photovoltaic efficiency†

Two-dimensional (2D) metal halide perovskites are renowned for their tunable optoelectronic properties and superior stability compared to their three-dimensional counterparts. However, their efficiency in photovoltaic devices has been hampered due to the disordered alignment of quantum wells and a tendency for in-plane growth. Herein, we proposed a de-templated crystallization strategy to control the crystallization kinetics of 2D perovskites via developing a stable intermediate phase in two-step deposition. By precisely adjusting the chemical interactions in the precursor solutions and driving the crystallization process, we successfully eliminate the templated in-plane growth near the liquid-air interface and promote the formation of highly out-of-plane orientated crystals, with the grain size exceeding 5 μm and carrier lifetime increased by four-fold. The optimized 2D perovskite solar cell achieves a high-power conversion efficiency (PCE) of 21.16% and a short-circuit current of 23.71 mA cm⁻². Additionally, the devices demonstrate remarkable stability, with a PCE decrease of less than 5% after exposure to 65 ± 10% humidity for 1100 hours, operation at 85 °C for 1077 hours, or continuous illumination for 1045 hours.