Flash-induced ultrafast recrystallization of perovskite for flexible light-emitting diodes

We report ultrafast recrystallization of perovskite (methylammonium lead tribromide, MAPbBr3) by flash light annealing (FLA) for light-emitting diode (LED) application. Intense near-infrared (NIR) peak spectrum (830 and 900 nm) of flash light could rapidly heat MAPbBr3 based LED structures over ∼320 °C without radiative damage. Cuboidal morphology of the perovskite active layer was evolved into the dense recrystallized structure with a noticeably small grain size (∼38 nm) by FLA, which significantly promoted the radiative recombination. Surface roughness (root mean square (RMS)) of the perovskite layer was decreased by 62% (from 8.47 to 3.22 nm) via FLA, while inhibiting the leakage current that limit current efficiency (CE) of perovskite LED (PeLED). Three dimensional temperature simulation was investigated for the mechanism of flash-induced MAPbBr3 recrystallization. Finally, FLA was successfully exploited for the flexible PeLEDs on polyethylene naphthalate substrates, which exhibited 252% larger CE compared to thermally annealed counterpart.