Optoelectronic Devices Based on Scaffold Stabilized Black‐Phase CsPbI 3 Nanocrystals

Abstract The optoelectronic properties of lead halide perovskites are intimately related to their crystalline phase. For the case of cesium lead iodide (CsPbI 3 ) several polymorphs meet the Goldschmidt tolerance factor, which determines their stability, and form broad band absorber and luminescent phases. However, at room temperature none of them are stable, which prevents their use in optoelectronics. In this work, bare CsPbI 3 nanocrystals are synthesized in the sub‐10 nm range in the “black”, light emitting, crystalline phase, using a pore controlled SiO 2 matrix that limits crystal size and confers a certain degree of strain that favors their stability. Quantum confinement effects allow the tuning of the optical properties of the CsPbI 3 nanocrystals by means of the crystal size. Their suitability as optoelectronic materials is demonstrated by building scaffold supported CsPbI 3 quantum dot based photovoltaic and light emitting devices.