Morphology optimization of perovskite films for efficient sky-blue light emitting diodes via a novel green anti-solvent dimethyl carbonate

Abstract

Quasi-two-dimensional (quasi-2D) perovskites have been identified as promising emitters for high-efficiency blue PeLEDs, attributed to the efficient radiative recombination resulting from the cascade energy transfer from low-n phases to high-n phases. Fine control of the phases with proper n values as well as excellent monodispersity is critical to achieving high EQEs. However, these phases, to some extent, are usually affected by the atmosphere and the temperature during the film-forming process, resulting in a wider distribution of lower n phases and higher n phases and thus undesirable efficiency. Decreasing the grain size is proved to be an effective way to optimize the PeLED performance through confining the exciton diffusion to promote radiative recombination. Herein, we introduce a facile approach to improve the efficiency of quasi-2D PeLEDs by effective morphology control via anti-solvent engineering using a green polar anti-solvent dimethyl carbonate (DMC). Attributed to the strong chemical interaction between DMC and PbBr₂·CsBr, the residual DMC in the perovskite can impede the grain coarsening during the heating process and preserve smaller grain size than that of the commonly used anti-solvent chloroform (CF). Furthermore, a better miscibility with the precursor solvent dimethyl sulfoxide (DMSO) and a higher boiling point benefit a more homogeneous morphology. As a result, the as-prepared sky-blue PeLED produces an obviously improved EQE of 6.43%, in contrast with the CF-treated device with an EQE of 5.28%. The present study might provide a new guide for anti-solvent engineering to develop high-efficiency PeLEDs.