Boosting the Performance of Transparent Perovskite LEDs through Methanol-Based Interface Optimization of PEDOT: PSS and CsPbBr 3

Transparent display technology is emerging as a pivotal direction for the future of the display industry. Metal halide perovskite materials, known for their outstanding optoelectronic properties, hold considerable promise for application in transparent perovskite light-emitting diodes (TPeLEDs). Nevertheless, the realization of high-performance TPeLEDs is still hindered by two major challenges: interfacial issues between the hole-injection layer (such as PEDOT: PSS) and the perovskite layer, and the difficulty of fabricating high-quality top transparent electrodes. In this work, we introduce a straightforward post-treatment strategy using methanol (MeOH) to simultaneously optimize the physical morphology, chemical composition, and electrical characteristics of PEDOT: PSS films. Results demonstrate that MeOH treatment effectively removes excess insulating PSS components from the PEDOT: PSS surface, yielding a smoother, more hydrophobic film with significantly enhanced conductivity. This optimized interface promotes the formation of a CsPbBr₃ perovskite layer with improved crystallinity, more uniform coverage, and reduced defect density, thereby facilitating the subsequent deposition of a high-quality transparent top electrode. Benefiting from these improvements, the resulting transparent green TPeLED exhibits outstanding overall performance: a maximum total external quantum efficiency (EQE) of 7.35% and an average visible transmittance of 63.51%. Additionally, the device shows significantly enhanced current efficiency, spectral stability, and operational lifetime. This study offers a simple yet effective approach to addressing key interfacial issues in TPeLEDs, advancing the application of perovskite materials in transparent displays.