Highly sensitive organic-inorganic heterojunction flexible photodetectors

J-H Seo, T-Y Oh, J. Park, W. Zhou, B-K Ju, Z. Ma
University of Wisconsin, Madison, US

Keywords: organic-inorganic heterojunction, flexible photodetector, silicon nanomembrane, pentacene


Heterostructures formed between inorganic and organic materials could lead to many unique device applications due to their unique physical properties, such as mechanical flexibility, large area, low temperature processability and high performance. Since most n-type organic semiconductor materials are unstable in air, while p-type organic semiconductor materials are more stable, many organic semiconductor applications can only use p-type organic semiconductor materials. The lack of stable n-type organic materials has been a major roadblock toward realizing many useful devices. In this paper, to overcome the lack of n-type organic semiconductor materials and to achieve high performance flexible electronics, we employ single-crystal Si nanomembranes (SiNMs) as the n-type materials and use pentacene as a p-type layer on the plastic substrate to form p-n junctions. We demonstrate that SiNMs can be easily integrated with pentacene. We further demonstrate a flexible hexagonal-shaped heterojunction p-n junction photodetectors. Due to the relatively high electron mobility of the silicon and low barrier height from the pentacene to silicon, organic-inorganic heterojunction photodetector showed very good photo-sensitivity as high as 1.8 × 104 times, the external quantum efficiency of 21.9% and the photo-responsivity of 0.94 mA/W with an incident light wavelength of 610 nm.