Room temperature femtowatt sensitivity remains a sought-after attribute, even among commercial inorganic infrared (IR) photodetectors (PDs). While organic IR PDs are poised to emerge as a pivotal sensor technology in the forthcoming Fourth-Generation Industrial Era, their performance lags behind that of their inorganic counterparts. This discrepancy primarily stems from poor external quantum efficiencies (EQE), driven by inadequate exciton dissociation (high exciton binding energy) within organic IR materials, exacerbated by pronounced non-radiative recombination at narrow bandgaps. Here, we unveil a high-performance organic Near-IR (NIR) PD via integer charge transfer between Poly[2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b]thiophene] (C-14PBTTT) donor (D) and Tetrafluorotetracyanoquinodimethane (TCNQF4) acceptor (A) molecules, showcasing strong low-energy subgap absorptions up to 2.5 µm. We observe that specifically, polaron excitation in these radical and neutral D-A blended molecules enables bound charges to exceed the Coulombic attraction to their counterions, leading to an elevated EQE (polaron absorption region) compared to Frenkel excitons. As a result, our devices achieve a high EQE of ∼10⁷%, femtowatt sensitivity (NEP) of ~0.12 fW Hz^-1/2 along a response time of ~81 ms, at room temperature for a wavelength of 1.0 µm. Our innovative utilization of polarons highlights their potential as alternatives to Frenkel excitons in high-performance organic IR PDs.

室温飞瓦级灵敏度仍然是一个广受欢迎的属性，即使在商用无机红外 （IR） 光电探测器 （PD） 中也是如此。虽然有机红外 PD 有望在即将到来的第四代工业时代成为一种关键的传感器技术，但它们的性能落后于无机同类产品。这种差异主要源于外部量子效率 （EQE） 差，这是由有机 IR 材料内的激子解离不足（高激子结合能）驱动的，而窄带隙处明显的非辐射复合加剧了这种情况。在这里，我们揭示了一种高性能有机近红外 （NIR） PD，通过聚[2,5-双（3-十四十二基噻吩-2-基）噻吩并[3,2-b]噻吩] （C-14PBTTT） 供体 （D） 和四氟四氰基喹代二甲烷 （TCNQF4） 受体 （A） 分子之间的整数电荷转移，展示了高达 2.5 μm 的强低能量亚间隙吸收。我们观察到，具体来说，这些自由基和中性 D-A 混合分子中的极化子激发使束缚电荷能够超过对其反离子的库仑吸引力，导致与 Frenkel 激子相比，EQE（极化子吸收区）升高。因此，我们的器件在室温下，波长为 1.0 μm，实现了 ∼10⁷% 的高 EQE，飞瓦灵敏度 （NEP） 为 ~0.12 fW ^Hz-1/2，响应时间为 ~81 ms。我们对极化子的创新利用突出了它们在高性能有机 IR PD 中作为 Frenkel 激子替代品的潜力。