Iqbal Muhammad Ahsan, Fang Xueqian, Abbas Yasir, Weng Xiaoliang, He Tingchao, Zeng Yu-Jia
School of Environment and Civil Engineering, Dongguan University of Technology, Dongguan, 523808, China.
Guangdong Provincial Key Laboratory of Intelligent Disaster Prevention and Emergency Technologies for Urban Lifeline Engineering, Dongguan University of Technology, Dongguan, 523808, China.
Light Sci Appl. 2024 Dec 9;13(1):318. doi: 10.1038/s41377-024-01695-9.
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 ∼10%, femtowatt sensitivity (NEP) of ~0.12 fW Hz 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.
即使在商用无机红外（IR）光电探测器（PD）中，室温飞瓦级灵敏度仍是一项备受追捧的特性。虽然有机红外光电探测器有望在即将到来的第四代工业时代成为关键的传感器技术，但其性能仍落后于无机同类产品。这种差异主要源于外部量子效率（EQE）较低，这是由有机红外材料内激子解离不足（激子结合能高）导致的，窄带隙处明显的非辐射复合进一步加剧了这种情况。在此，我们通过聚[2,5-双（3-十四烷基噻吩-2-基）噻吩并[3,2-b]噻吩]（C-14PBTTT）供体（D）和四氟四氰基喹二甲烷（TCNQF4）受体（A）分子之间的整数电荷转移，揭示了一种高性能有机近红外（NIR）光电探测器，其在高达2.5μm的波长处展现出强烈的低能亚带隙吸收。我们特别观察到，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其与抗衡离子的库仑吸引力，从而导致与弗伦克尔激子相比，EQE（极化子吸收区域）有所提高。结果，我们的器件在室温下对于1.0μm波长实现了约10%的高EQE、约0.12 fW Hz的飞瓦级灵敏度（NEP）以及约81 ms的响应时间。我们对极化子的创新利用突出了它们在高性能有机红外光电探测器中作为弗伦克尔激子替代品的潜力。
