Recent advances in organic near-infrared photodiodes

Solution-processable organic photodiodes compensate well for the shortages of the traditional inorganic photodetectors in terms of their unique features, such as rich in varieties, low-cost manufacturing, light weight, high flexibility, and large-area scalability. Owing to the tunable optoelectronic properties of organic materials, both panchromatic and narrowband organic photodiodes have been achieved. In this review, we provide a comprehensive overview of the recent progress of organic near-infrared (NIR) photodiodes, mainly focusing on diverse device architectures toward superior performance. The key to achieving a high specific detectivity is a high responsivity while keeping dark current low. Interfacial engineering plays a critical role in suppressing the dark current, and has been identified as an essential approach for maximizing detectivity of organic photodiodes. Besides, optimization of photoactive layer thickness and morphology is also highly desirable. As to narrowband organic NIR photodiodes, we highlight three primary strategies: (i) the use of truly narrowband absorbers; (ii) the manipulation of internal quantum efficiency via charge collection narrowing; and (iii) the incorporation of a resonant optical microcavity structure to exploit charge-transfer absorption. The latter two creative approaches allow for response tuning by simply adjusting the thickness of photoactive layer and cavity, respectively.