Vertically Phase Separated Photomultiplication Organic Photodetectors with p-n Heterojunction Type Ultrafast Dynamic Characteristics.

Abstract

Photomultiplication (PM)-type organic photodetectors (OPDs), which typically form a homogeneous distribution (HD) of n-type dopants in a p-type polymer host (HD PM-type OPDs), have achieved a breakthrough in device responsivity by surpassing a theoretical limit of external quantum efficiency (EQE). However, they face limitations in higher dark current and slower dynamic characteristics compared to p-n heterojunction (p-n HJ) OPDs due to inherent long lifetime of trapped electrons. To overcome this, we have developed a new PM-type OPD that demonstrates ultrafast dynamic properties through a vertical phase separation (VPS) strategy between the p-type polymer (host) and n-type acceptor (dopant), referred to as VPS PM-type OPDs. Notably, VPS PM-type OPDs show a remarkable increase (by three orders of magnitude) in -3dB cut-off frequency (120kHz) and over a 200-fold faster response time (rising time = 4.8 µs, falling time = 8.3 µs) compared to HD PM-type OPDs, while maintaining high EQE of 1,121% and specific detectivity of 2.53 × 1013 Jones at -10V. The VPS PM OPD represents a groundbreaking advancement by demonstrating the coexistence of p-n HJ and PM modes within a single photoactive layer for the first time. This innovative approach holds the potential to enhance both static and dynamic properties of OPDs. This article is protected by copyright. All rights reserved.