Functionalized Interlayers in Self-Powered Organic Photodiodes for Enhanced Near-Infrared Sensing

There is a growing interest in fabricated organic material-based photodiodes (OPDs) since they are lightweight, flexible, and cost-effective to manufacture. Notably, they exhibit near-infrared photo-sensing capabilities that are self-powered, a feature attributed to the tunable optical properties of organic semiconductor (OSC) materials. Nonetheless, the application of OPDs in the semiconductor industry encounters challenges compared to their inorganic counterparts, such as low sensitivity and limited durability. In this study, a self-powered OPD using a poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo [1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)]:biaxial active layer of phenyl-C70-butyric acid methyl ester (PTB7-Th:PC₇₀BM) and an organic hole transport layer (HTL) composed of poly(3,4-ethylenedioxythiophene) and poly(styrene sulfonate) (PPY:PSS) is developed. These results highlight the effectiveness of PPY:PSS as an HTL, demonstrating distinct improvements in efficiency, photosensitivity, photo-detectivity, and operational stability of the OPD when the weight ratio between the PPY and PSS is 1:2.