Thermal-induced interface degradation in perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) have experienced rapid improvements in device efficiency during the last several years. However, the operational instability of PeLEDs remains a key barrier hindering their practical applications. A fundamental understanding of the degradation mechanism is still lacking but will be important to seek ways to mitigate these unwanted processes. In this work, through comprehensive characterizations of the perovskite emitters and the interfacial contacts, we figure out that Joule heating induced interface degradation is one of the dominant factors affecting the operational stability of PeLEDs. We investigate the interfacial contacts of PeLEDs based on a commonly used device structure, with an organic electron transport layer of 1,3,5-tris(N-phenylbenzimiazole-2-yl)benzene (TPBi), and observe obvious photoluminescence quenching of the perovskite layer after device operation. Detailed characterizations of the interlayers and the interfacial contacts reveal that photoluminescence quenching is mainly due to the element inter-diffusion at the interface induced by the morphological evolution of the TPBi layers under Joule heating during the operation of PeLEDs. Our work provides direct insights into the degradation pathways and highlights the importance of exploring intrinsically stable interlayers as well as interfacial contacts beyond the state-of-the-art to further boost the operational stability of PeLEDs.