Flash light induced recrystallization of perovskite for high efficiency light-emitting diodes

Abstract

Organic-inorganic hybrid perovskite (PVSK) has received huge attentions as a promising materials for next generation light emitting diodes (LEDs) because of its high color purity, low cost and many other advantages in spite of low device efficiency. To enhance the perovskite LED efficiency, the morphology of PVSK film such as grain size and surface roughness is carefully controlled due to its intrinsic properties (long diffusion length and small binding energy of excitons). However, the current method to control the morphology (A-NCP) to solve it has some limitations in reducing grain size further and surface roughness. So, other solution for efficient and convenient control was required.

Here, we introduced flash light annealing (FLA) inducing ultrafast melting and recrystallization of PVSK film in microsecond scale that can easily control the morphology of film. The grain size and film roughness were clearly reduced by simple modifying of flash light intensity compared with TA treatment. The trap density reduction due to densification of film after optimized FLA was also investigated by PL analysis and photothermal degradation mechanism was suggested by XPS data. Finally, we fabricated FLA perovskite LED and 2.5 times higher current efficiency (1.05 cd/A) than TA treated device was observed at the optimized condition showing smallest average grain size (~ 38 nm) without any degradation.