In-situ inkjet printing of perovskite single-crystal array embedded PDMS film for wearable light-emitting devices.

Metal halide perovskites are promising light-emitting materials for applications such as wearable lighting devices and flat panel displays due to their high photoluminescence efficiency, high color purity and facile solution processability. However, the intrinsic ambient instability and crystal friability issues have fundamentally hindered the practical applications of perovskites. Here we solve this problem through a liquid to liquid self-encapsulation inkjet-printing technique. Perovskite inks are directly inkjet-printed into the liquid polydimethylsiloxane (PDMS) precursor to in-situ form the self-encapsulation perovskite single crystal embedded PDMS structure. We show that the space confined effect of the liquid PDMS precursor can significantly retard the perovskite crystallization process and promote the embedded-growth of perovskite single crystals in PDMS. Benefiting from the sealing function of the PDMS, the printed perovskite single crystals show excellent ambient stability and flexibility. Furthermore, we demonstrate that wafer-scale air-stable and flexible perovskite fluorescent patterns can be produced in PDMS by direct inkjet printing, which is cost effective and free of complex microfabrication process. This method provides a facile approach to scalable fabrication of air-stable and wearable perovskite fluorescent patterns, which will be of great significance for potential application in perovskite light-emitting diodes display.