Thermally Reliable Copolymer-Based Photodetectors Based on Thermal-Induced Bandgap Broadening Characteristic

Photodetectors (PDs) are currently widely employed in communications, imaging, sensing, and other fields. However, elevated temperatures significantly exacerbate noise effects, thereby degrading device performance and operational lifetime. Notably, the thermal-induced bandgap broadening (TBB) phenomenon in copolymer organic semiconductors (OSCs) offers a promising solution to this challenge. In this work, we diketo pyrrolopyrrole-thieno [3,2-b] thio-phene (DPPT-TT) as the active layer, integrated with metallic nanoparticle nanostructures. Comprehensive characterization confirmed that the TBB effect effectively suppresses dark current under high-temperature conditions. Benefiting from this phenomenon, the device exhibits an ultralow dark current density of $2.44\times 10^{-{10}}$ A/cm² at 353 K. Under a 0.2 V bias, it achieves remarkable performance metrics, including an external quantum efficiency (EQE) of 71.47% and a theoretical specific detectivity ( ${D}_{\textit {th}}^{\ast }\text {)}$ of $5.12\times 10^{{13}}$ Jones ( $\lambda =780$ nm). To elucidate and quantitatively analyze the physical role of TBB in optoelectronic devices, we established a block filling model (BFM). Through combined molecular dynamics (MDs) simulations and first-principles calculations, this model successfully simulates the physical properties of DPPT-TT and provides a quantitative analysis of temperature-induced bandgap variations. Our experimental investigations systematically analyzed the temperature-dependent flocculent molecular disorder in copolymer OSCs, establishing a theoretical foundation for developing thermally reliable photodetectors. These findings provide crucial insights into high-temperature operation mechanisms and device optimization strategies.