Temperature-Dependent Detectivity of Near-Infrared Organic Bulk Heterojunction Photodiodes

• Published in: ACS applied materials & interfaces Vol. 9; no. 2; pp. 1654 - 1660
• Main Authors: Wu, Zhenghui, Yao, Weichuan, London, Alexander E, Azoulay, Jason D, Ng, Tse Nga
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 18.01.2017
• Subjects: activation energy; temperature dependence; near-infrared photodetector; organic bulk heterojunction; detectivity; physiological sensing
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.6b12162

Bulk heterojunction photodiodes are fabricated using a new donor–acceptor polymer with a near-infrared absorption edge at 1.2 μm, achieving a detectivity up to 1012 Jones at a wavelength of 1 μm and an excellent linear dynamic range of 86 dB. The photodiode detectivity is maximized by operating at zero bias to suppress dark current, while a thin 175 nm active layer is used to facilitate charge collection without reverse bias. Analysis of the temperature dependence of the dark current and spectral response demonstrates a 2.8-fold increase in detectivity as the temperature was lowered from 44 to −12 °C, a relatively small change when compared to that of inorganic-based devices. The near-infrared photodiode shows a switching speed reaching up to 120 μs without an external bias. An application using our NIR photodiode to detect arterial pulses of a fingertip is demonstrated.