Terminal Fluorination Modulates Crystallinity and Aggregation of Fully Non-Fused Ring Electron Acceptors for High-Performance and Durable Near-Infrared Organic Photodetectors.

Abstract

High dark current density (J_d) severely hinders further advancement of near-infrared organic photodetectors (NIR OPDs). Herein, we tackle this grand challenge by regulating molecular crystallinity and aggregation of fully non-fused ring electron acceptors (FNREAs). TBT-V-F, which features fluorinated terminals, notably demonstrates crystalline intensification and a higher prevalence predominance of J-aggregation compared to its chlorinated counterpart (TBT-V-Cl). The amalgamation of advantages confers TBT-V-F-based OPDs with lower nonradiative energy loss, improved charge transport, decreased energetic disorder, and reduced trap density. Consequently, the corresponding self-powered OPDs exhibit a 40-fold decrease in J_d, a remarkable increase in detectivity (D*_sh), faster response time, and superior thermal stability compared to TBT-V-Cl-based OPDs. Further interfacial optimization results in an ultra-low J_d of 7.30×10^-12 A cm^-2 with D*_sh over 10¹³ Jones in 320-920 nm wavelength and a climax of 2.2×10¹⁴ Jones at 800 nm for the TBT-V-F-based OPDs, representing one of the best results reported to date. This work paves a compelling material-based strategy to suppress J_d for highly sensitive NIR OPDs, while also illustrates the viability of FNREAs in construction of stable and affordable NIR OPDs for real-world applications.