Designing Nonplanar Electron Acceptors for High-Performance Organic Photodetectors: Mechanism Analysis and Application in Gesture Recognition

Realizing low dark current density (J_d) while maintaining high photoresponse is crucial yet challenging for organic photodetectors (OPDs). In this work, two nonplanar small molecule electron acceptors, BTTPCN-F and BTTPCN-Cl, were developed. The OPDs based on them achieved ultralow J_d down to 2.95 × 10^-13 A cm^-2 and exceptionally high shot noise-limited detectivity (D_sh*) up to 1.12 × 10¹⁵ Jones, which are the lowest J_d and highest D_sh* reported for self-powered OPDs to date. The ultralow J_d is attributed to the high reorganization energy and small intermolecular electronic coupling in these nonplanar molecules. On the other hand, their large molecular dipole moment and high dielectric constant contribute to low exciton binding energy, leading to high photoresponse. Consequently, they can work as effective dark current suppressors for achieving high-performance binary or ternary OPDs. A dynamic gesture recognition system based on BTTPCN-Cl OPD was developed, which can accurately identify the gesture input. This work unveils the great potential of high dielectric constant nonplanar organic semiconductors for photodetection.