Polymer-modified CsPbI2Br films for all-inorganic planar perovskite solar cells with improved performance

All-inorganic CsPbI 2 Br perovskite with relatively high phase stability and a suitable band gap has been considered as a promising candidate for photovoltaic application. However, in comparison with its organic–inorganic counterparts, it still shows unsatisfactory efficiency and high moisture sensitivity. Here, polyethylene glycol (PEG) is introduced into the CsPbI 2 Br precursor solution. It is revealed that Lewis base PEG interacts with Pb 2+ , which can slow down the crystallization rate, regulate the energy levels, and passivate the defect density of CsPbI 2 Br films. As a result, the optimized devices with PEG exhibit a power conversion efficiency (PCE) of 13.59% under one sun illumination (100 mW cm ‒2 ), which is considerably higher than that of the control devices (10.09%), owing to the reduced nonradiative recombination losses for the former CsPbI 2 Br films. The results demonstrate that using polymer additives to improve the device performance is an effective strategy for all-inorganic perovskite solar cells.