2, KAIST, Daejeon, , Korea (the Republic of)
3, Kyung Hee University, Yongin-si, , Korea (the Republic of)
The organic-inorganic halide perovskites (OIHPs) as a next-generation light emitter have been vigorously studied. To achieve highly efficient OIHP-based optoelectronic devices, the addition of additives to the OIHPs is one of the promising approaches. However, we found that the conventional crystal growth mechanism of spin-coated OIHP films is dramatically affected by impurity effect when additives with an above a critical concentration are directly added to the OIHP precursor solutions to fabricate an additive mixed OIHP hybrid film. In this research, we have identified the crystallization kinetics including a crystal coarsening, which is not suitable for LED applications, of the OIHP film with additives, and have devised a method to effectively overcome a crystal coarsening and to fabricate additive:OIHP hybrid film effective for LED application, thus realizing a highest EQE of pure green PeLED. The fabricated additive:OIHP hybrid film showed high radiative recombination rate by the defect healing effect, and low charge accumulation, which is due to low free carrier density by high radiative recombination rate and effective exciton confinement, and dramatically improved a half-lifetime of PeLEDs were also investigated in PeLEDs. Moreover, the highly changed optical parameters, which induced a low optical loss in the PeLEDs, were firstly observed, and this optical effect is also confirmed by performing the optical simulation.