Efficient Infrared‐Detecting Organic Semiconductors Featuring a Tetraheterocyclic Core with Reduced Ionization Potential

Abstract Infrared organic semiconductors are crucial in organic optoelectronics, yet high‐performance materials with photoresponse beyond 1.1 μm (the limit of crystalline silicon) remain scarce due to the limit of building blocks including strong electron‐donating units. Here, we report an asymmetric tetraheterocycle (TPCT) with a reduced ionization potential of 6.18 eV relative to those reported dithiophene‐based electron‐donating blocks, and TPCT‐2F and TPCTO‐2F constructed with TPCT as the core exhibit absorption onset up to 1 μm and 1.4 μm, respectively. Especially, TPCTO‐2F possesses a narrow band gap of 1.00 eV and displays a small Urbach energy of 22.0 meV comparable to or even lower than those of some typical inorganic short‐wave infrared (SWIR) semiconductors (13–44 meV). The organic photodetectors (OPDs) based on TPCT‐2F achieve a peak detectivity ( D *) of 2.2×10 13 Jones at 810 nm under zero bias, among the highest values for reported OPDs and on par with commercial silicon photodetectors. Impressively, TPCTO‐2F‐based OPDs demonstrate a wide response from 0.3 to 1.4 μm and high D * comparable to germanium photodetector at wavelengths <1.2 μm with a maximum D * of 2.3×10 11 Jones at 1.06 μm in SWIR region.