Spray-Printed Light-Emitting Diodes with Perovskite/Polymer Composite Emitters on Various Transparent Substrates

Advancements in printing techniques are essential for fabricating next-generation displays. Lead halide perovskites demonstrate great potential as light emitters of solution-processed light-emitting diodes (LEDs). In particular, the perovskite/polymer composite emitters exhibit exceptional luminescent characteristics, mechanical flexibility, and environmental stability due to the improved film morphologies and defect passivation achieved through the introduction of polymer additives. However, solution-based conventional processing methods, such as spin-coating, slot-die coating, and inkjet printing are limited to planar substrates. Spray printing is a promising coating process, which can be applied for depositing composite emitters across various substrate types. In this study, we employed a spray-coating process to design planar and curved perovskite LEDs (PeLEDs) by incorporating methylammonium lead bromide (MAPbBr₃) and poly(vinylpyrrolidone) (PVP) composite-based emitters. PVP played a critical role in enhancing the MAPbBr₃ morphology through a strong coordination between Pb²⁺ ions and lone pair electrons in the PVP chains. Under optimized conditions of air pressure, spray time, and PVP concentration, the planar PeLEDs achieved a maximum luminance (L_max) of 18,850 cd m^-2, a current efficiency of 12.26 cd A^-1, and an external quantum efficiency of 4.19%. The flexible PeLEDs retained their performance even after 1000 bending cycles at a bending radius of 10 mm. Furthermore, the spray-printed curved PeLEDs constructed on glass pipet- and spherical glass-based substrates demonstrated L_max values of 3792 and 3368 cd m^-2, respectively.