Near-infrared organic photodetectors outperform Si photodetectors: introducing an all-fused-ring acceptor into active layers for ultra-low trap density

Abstract

Near-infrared (NIR) organic photodetectors (OPDs) hold enormous commercial potential in wearable biosensing and imaging applications. However, their sensitivity remains comparatively lower than that of commercially available silicon-based photodetectors (Si PDs). In this study, we present highly sensitive NIR OPDs by incorporating an all-fused-ring small molecule acceptor, FM4, with low trap density into a conventional active layer system. FM4 effectively reduces traps in the active layer, resulting in a decrease in trap density from 1.57 × 10¹⁵ to 8.86 × 10¹⁴ cm⁻³. Consequently, under −1 V bias, the OPD device with FM4 as the third component achieves an ultra-low real-measured noise current of 7.56 × 10⁻¹⁵ A Hz^−1/2 at 1 kHz, lower than that of commercial Si PDs, which is primarily attributed to the substantial decrease in trap density within the active layer. Due to its ultra-low noise current, the ternary device exhibits a high specific detectivity of 1.83 × 10¹³ Jones at 840 nm under −1 V bias and a broad linear dynamic range of 155 dB. Its sensitivity exceeds that of Si PDs. Furthermore, this sensitive OPD device has been successfully utilized in single-pixel low-light imaging, delivering superior image clarity compared to Si PDs.