In situ polymer-covered annealing strategy for high-efficiency carbon-electrode CsPbIBr2 solar cells

Abstract

CsPbIBr₂ has attracted intense attention as an absorber material of all-inorganic perovskite solar cells (PSCs), owing to its upgraded stability and suitable bandgap. Yet, the efficiency level of CsPbIBr₂ PSCs is still far below those of other all-inorganic PSCs, largely because of the inferior morphology and crystallization properties of solution-processed CsPbIBr₂ films. Herein, we propose for the first time an in situ polymer-covered annealing strategy to modify the crystallization behavior of one-step-deposited CsPbIBr₂ film, which is performed through spin-coating of poly(methyl methacrylate) (PMMA) solution upon CsPbIBr₂ precursor film before annealing. By optimizing the concentration of PMMA solution, a CsPbIBr₂ film with large-size grains, [110]-preferred orientation, reduced halide segregation, stoichiometric composition, and decreased non-radiative recombination can be acquired, which lead to the improved transport and suppressed non-radiative recombination of charge carriers for the resulting PSC. Hence, the optimum carbon-electrode PSC exhibits a significantly enhanced efficiency from 8.71% to 10.50%, which is better than that of nearly all the CsPbIBr₂ PSCs with the same configuration reported earlier.