Synthesis of Photoconductive Polymers and Understanding Origin to Decrease Dark Current Density for Developing High-Performance Organic Photodetectors
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In this study, we focused on the design and development of photoconductive polymers (PCPs) for use in p-n bulk heterojunction organic photodetectors (OPDs). By using benzo[1,2-d:4,5-d']bis(oxazole)-based PCPs and incorporating π-spacer molecular engineering, we intended to enhance charge transport properties and decrease dark current density (Jd) in the OPDs. Our analysis of the hole charge-transfer (CT) state energy revealed that hole accumulation at the CT state is critical for achieving low Jd and fast signal response times, surpassing the CT state energy itself. The custom OPDs we created exhibited impressive responsivity (R) of 0.43 A/W and specific detectivity (D*) of 6.85x10^12 Jones at -1 V with 532 nm LED (5.0 mW cm^-2) illumination. Additionally, the integration of π-spacers into the PCPs significantly improved the dynamic properties of the devices, achieving a -3 dB cut-off frequency of 200.4 kHz along with ultrafast rising/falling response times of 2.3 and 2.8 μs, respectively.