Effect of self-assembled monolayer on stability of perovskite LEDs

Perovskite light-emitting diodes (LEDs) with different self-assembled monolayers (SAMs), namely 2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz), [4-(3,6-dimethyl-9H-carbazol- 9-yl)butyl] phosphonic acid (Me-4PACz), and [2-(3,6-Dichloro-9H-carbazol-9-yl)ethyl]phosphonic acid (Cl-2PACz), have been investigated. We find that the underlying SAM affects the perovskite morphology despite the use of poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(4,4′-(N-(4-butylphen-yl)))] (TFB) hole transport layer between the SAM and the perovskite. Despite similar device performance in terms of maximum luminance and external quantum efficiency, the devices exhibit significant differences in lifetime which correlate with perovskite thin film morphology. We show that significant roughness is detrimental to the device stability. The devices with 2PACz SAM, which exhibit the most favorable film morphology, exhibit T 50 lifetime of 1.43 h.