An n-Type All-Fused-Ring Molecule with Photoresponse to 1000 nm for Highly Sensitive Near-Infrared Photodetector

Most of all-fused-ring pi-conjugated molecules have wide or medium bandgap and show photo response in the visible range. In this work, an all-fused-ring n-type molecule, which exhibits an ultrasmall optical bandgap of 1.22 eV and strong near-infrared (NIR) absorption with an onset absorption wavelength of 1013 nm is reported. The molecule consists of 14 aromatic rings and has electron donor-acceptor characteristics. It exhibits excellent n-type properties with low-lying HOMO/LUMO energy levels of -5.48 eV/-3.95 eV and high electron mobility of 7.0 x 10(-4) cm(2) V-1 s(-1). Most importantly, its thin film exhibits a low trap density of 5.55 x 10(16) cm(-3) because of the fixed molecular conformation and consequently low conformation disorder. As a result, organic photodetector (OPD) based on the compound exhibits a remarkably low dark current density (J(d)) of 2.01 x 10(-10) A cm(-2) at 0 V. The device shows a shot-noise-limited specific detectivity (D-sh*) of exceeding 10(13) Jones at 400-1000 nm wavelength region with a peak specific detectivity of 4.65 x 10(13) Jones at 880 nm. This performance is among the best reported for self-powered NIR OPDs.

Automated summary

This study reports an all-fused-ring n-type molecule with an ultrasmall optical bandgap (1.22 eV) and strong near-infrared (NIR) absorption. The molecule consists of 14 aromatic rings and displays excellent n-type properties, with low-lying HOMO/LUMO energy levels (-5.48 eV/-3.95 eV) and high electron mobility (7.0 x 10(-4) cm(2) V-1 s(-1)). The thin film of this molecule exhibits low trap density (5.55 x 10(16) cm(-3)) due to fixed molecular conformation and low conformation disorder. Consequently, the organic photodetector (OPD) based on this compound demonstrates remarkably low dark current density (2.01 x 10(-10) A cm(-2) at 0 V) and high specific detectivity (exceeding 10(13) Jones at 400-1000 nm wavelength region, with a peak of 4.65 x 10(13) Jones at 880 nm). This performance is among the best reported for self-powered NIR OPDs.