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 bandgap 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 2.2×1013 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 <1.3 μm with a maximum D* of 2.3×1011 Jones at 1.06 μm in SWIR region.