Unlocking the Bifunctional Potential of NPB:OXD-7 Exciplex in Organic Light Emitting Diodes and UV- Photodetectors

Abstract

While highly efficient exciplex-host organic light emitting diodes (OLEDs) have been extensively studied, their untapped potential for multifunctional applications remains largely unexplored. In this study, exciplex emission by utilizing the commonly used hole transport material (HTM) N,N′-Di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) and the electron transport material (ETM) 1,3-Bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazol-5-yl]benzene (OXD-7) was investigated. The dual functionality of NPB:OXD-7 exciplex for OLEDs and photodetectors was explored considering the influence of surface potential in organic semiconductor films. The significant surface potential of OXD-7 facilitated spontaneous exciplex dissociation at the molecular interface of NPB and OXD-7, generating a photocurrent, under Ultraviolet (UV) exposure to NPB:OXD-7 mixed layer, allowing the device to function as an efficient UV detector. Devices with higher OXD-7 concentrations exhibited enhanced UV absorption, though at the expense of exciplex emission. Specifically, an NPB:OXD-7 device with a 1:3 ratio demonstrated exceptional performance as a UV detector but inferior performance as an OLED. This work pioneers the exploration of multifunctional capabilities in exciplex-type OLEDs, expanding their role beyond light emission.