Hexagonal Lead-Free Cs₂AgBiI₆ Perovskite Nanocrystals: A Promising Material for Solar Cell Application

Abstract

Lead halide perovskite (LHP) nanocrystals (NCs) have extensive applications in optoelectronics. However, their high toxicity and low stability inhibit their commercialization. Herein, lead-free Cs2AgBiI6 NCs with a hexagonal phase are synthesized using a hot-injection process, which exhibit a band gap of 2.29 eV, a high absorption coefficient (∼2.8 × 105 cm–1), and a symmetric and narrow photoluminescence peak (full width at half-maximum = 10 nm). In addition, the hexagonal Cs2AgBiI6 NC films exhibit high resistance to heat, humidity, and illumination in air. Solar cells based on hexagonal Cs2AgBiI6 NCs are fabricated for the first time, achieving a power conversion efficiency (PCE) of 0.076%, which confirms its promising potential for photovoltaic applications.