High-Open-Circuit-Voltage Solar Cells Based on Bright Mixed-Halide CsPbBrI2 Perovskite Nanocrystals Synthesized under Ambient Air Conditions

Lead halide perovskite nanocrystals (NCs) are currently emerging as one of the most interesting solution-processed semiconductors because they possess high photoluminescence quantum yield (PLQY) and color tunability through anion exchange reactions or quantum confinement. Here, we show efficient solar cells based on mixed-halide (CsPbBrI2) NCs obtained via anion exchange reactions under ambient conditions. We performed anion exchange reactions in concentrated NC solutions with I-, thus inducing a PL red shift up to 676 nm and obtaining a high PLQY in film (65%). Solar cell devices operating in the wavelength range 350-660 nm were fabricated in air with two different deposition methods. The solar cells display a photoconversion efficiency of 5.3% and open circuit voltage (V-oc) up to 1.31 V, among the highest reported for perovskite-based solar cells with band gap below 2 eV, clearly demonstrating the potential of this material.