Guanidinium iodide modification enabled highly efficient and stable all-inorganic CsPbBr3 perovskite solar cells

Abstract The preparation of high-quality perovskite thin films with low grain boundaries and defect states plays an important role in determining the photovoltaic performance and stability of perovskite solar cells (PSCs). It has been proved that the inorganic CsPbBr3 perovskite material has unique stability. However, the wide band gap and small light absorption range limit the power conversion efficiency (PCE) of the corresponding devices. Here, we report that the addition of guanidine iodide (GAI) into CsPbBr3 precursor solution can greatly improve the quality of CsPbBr3 film, leading to inhibition of interfacial recombination, promotion of charge migration and reduction of trap state density. Ultimately, the planar PSC with GAI modified CsPbBr3 film yields a champion efficiency of 8.54%, much higher than the control one (6.56%).