Electron‐Rich Heptacyclic S,N Heteroacene Enabling C‐Shaped A‐D‐A‐type Electron Acceptors With Photoelectric Response beyond 1000 Nm for Highly Sensitive Near‐Infrared Photodetectors

Abstract

A highly electron-rich S,N heteroacene building block is developed and condensed with FIC and Cl-IC acceptors to furnish CT-F and CT-Cl, which exhibit near-infrared (NIR) absorption beyond 1000 nm. The C-shaped CT-F and CT-Cl self-assemble into a highly ordered 3D intermolecular packing network via multiple π-π interactions in the single crystal structures. The CT-F-based organic photovoltaic (OPV) achieved an impressive efficiency of 14.30% with a broad external quantum efficiency response extending from the UV-vis to the NIR (300-1050 nm) regions, outperforming most binary OPVs employing NIR A-D-A-type acceptors. CT-Cl possesses a higher surface energy than CT-F, promoting vertical phase segregation and resulting in its preferential accumulation near the bottom interface of the blend. This arrangement, combined with the lower HOMO energy level of CT-Cl, effectively reduces undesired hole and electron injection under reverse voltage. The PM6:CT-Cl-based organic photodetectors (OPDs) devices achieved an ultra-high shot-noise-limited specific detectivity (D_sh*) values exceeding 10¹⁴ Jones in the NIR region from 620 to 1000 nm, reaching an unprecedentedly high value of 1.3 × 10¹⁴ Jones at 950 nm. When utilizing a 780 nm light source, the PM6:CT-Cl-based OPDs show record-high rise/fall times of 0.33/0.11 µs and an exceptional cut-off frequency (f_-3dB) of 590 kHz at -1 V.