Low‐Bandgap Polymers for High‐Performance Photodiodes with Maximal EQE near 1200 nm and Broad Spectral Response from 300 to 1700 nm

Abstract Polymer photodiodes with broad spectral response above 1500 nm can be used for imaging in the near‐infrared window of the atmosphere. Three low‐bandgap polymers based on 3,6‐dithiophen‐2‐yl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (DPP), [1,2,5]thiadiazolo[3,4‐g]quinoxaline (TQ), benzobisthiadiazole (BBT), and dithienopyrrole (DTP) are designed and synthesized. No‐gain and gain polymer photodiodes with polymers:PC₇₁BM as active layer materials and with aluminum doped ZnO nanoparticles:2,9‐bis(3‐(dimethylamino)propyl)anthra[2,1,9‐def:6,5,10‐d′e′f′]diisoquinoline‐1,3,8,10(2H,9H)‐tetraone (AZO:PDIN), MoO₃, and 2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP) as interlayer materials are prepared. No‐gain photodiodes based on polymer P1 exhibit the external quantum efficiency (EQE) of 7.8% at 1200 nm, which is among the best values of polymer photodiodes known to date. Gain photodiodes based on P1 and P3 also exhibit a maximal EQE near 1200 nm. In addition, gain photodiodes based on P1 have a specific detectivity over 10¹³ Jones in 300–1360 nm and spectral response in the region of 300–1700 nm.