Tuning Absorption State and Intermolecular Potential of Organic Semiconductors for Narrowband Ultraviolet Photodetection

Narrowband response of organic semiconductors determines the band selectivity and anti-interference of the organic photodetectors, which are pursued for a long time but have not yet been resolved in the UV band. Herein, a feasible strategy is developed to realize narrowband UV response by tuning the absorption state and intermolecular potential of organic semiconductors. The as-designed non-Donor-Acceptor molecule, 2,5-diphenylthieno[3,2-b]thiophene (2,5-DPTT), exhibits narrowband absorption by fully suppressing the charge transfer state absorption. Simultaneously, the intermolecular potential is significantly enhanced (to ≈90 KJ mol^-1) by modulating the molecular planarity. Consequently, the UV photodetector based on 2,5-DPTT achieves excellent narrowband response at 310 nm wavelength and a record-breaking photosensitivity (P = 1.21 × 10⁶) in the deep UV range. In the demonstration application of flame alarm, the flame detector based on 2,5-DPTT single crystal exhibits excellent anti-interference capability. This work provides the inspiration for designing narrowband responsive organic semiconductors and building up multifunctional optoelectronic devices.