Red-emitting micro PeLEDs for UHD displays by using capillary force lithography

Conventional techniques for fabricating micro-light-emitting diode (LED) pixel arrays for ultra-high definition (UHD) displays have drawbacks of high cost and complex processing. Furthermore, it is technically difficult to improve the display resolution using traditional patterning and deposition processes. As the size of the chips decreases to the microscale, there is an increase in the cost due to the additional transfer process, and inaccuracy of mechanical positioning during the repeated transfer process. To solve these problems, a micro-patterning method using capillary force lithography was introduced. Using this method, a 10 µm-scale CsPbBr_xI_3-x micro-pattern array was fabricated. Moreover, multi-ligand (NMABr_0.7I_0.3–DMPDAB–PDAB) and poly(ethylene oxide) (PEO) as a hydrophilic polymer were added to the perovskite precursors to control the heterogeneous nucleation and crystal growth during the patterning process. To demonstrate the feasibility of the 10 µm-scale micro-pattern array for the micro-perovskite LEDs (micro-PeLEDs), CsPbBr_xI_3-x–multi-ligand–PEO precursors were adopted. These micro-PeLEDs exhibited characteristic emission at 650.9 nm with a luminance of 688.4 cd m⁻² and external quantum efficiency of 5.9% at 4 V.