Optimization of the optical properties of lead-free 0D Cs3Cu2I5 perovskite films via hydroiodic acid

Recently, zero-dimensional (0D) lead-free Cs 3 Cu 2 I 5 materials have become one of the most attractive research hotspots in the optoelectronic field owing to their simple preparation method and long-term air stability. However, the photoluminescence quantum yield (PLQY) of the blue luminescence of Cs 3 Cu 2 I 5 still lags behind those of the green and red luminescence of lead halide perovskites. Herein, 0D lead-free Cs 3 Cu 2 I 5 films modulated by hydroiodic acid (HI) with a high PLQY of blue luminescence are addressed. The results show that the particle size of the Cs 3 Cu 2 I 5 films decreases as the added amount of HI increases, from 223.3 (without HI) to 200.7 nm (with 0.076 mmol HI). The Cs 3 Cu 2 I 5 films with 0.038 mmol HI display the lowest root-mean-square roughness of 14.7 nm. Moreover, the as-prepared films all exhibit blue luminescence at 445 nm, and the PLQY of Cs 3 Cu 2 I 5 films reaches 85.3% when 0.038 mmol HI is added. Most importantly, the obtained films demonstrate long-term air stability under an ambient atmosphere, and the crystal structure and PLQY of Cs 3 Cu 2 I 5 films have no obvious variation after 150 days. This air-stable lead-free blue luminescence with high PLQY provides a new strategy to promote the blue luminescence optical property of halide perovskite materials. Graphical Abstract