Development of Conjugated Polymers from Pharmaceutical Intermediates for High‐Performance Panchromatic Organic Photodetectors and Fingerprint Image Sensors

Fingerprint-on-display (FoD) sensors utilizing organic photodetectors (OPDs) are nearing commercialization, making it crucial to develop novel conjugated polymers that can be used as the active layer for this technology. These polymers should meet several requirements in terms of patent rights, large-scale synthesis, and OPD performance. In this study, novel conjugated polymers containing electron-withdrawing building blocks, easily synthesized from a 2-aminothiazole-4-carboxylate Schiff base commonly used as a pharmaceutical intermediate, are developed for high-performance OPDs and FoD sensors. Through alkyl chain engineering of the synthesized polymers, the highest photocurrent density and the lowest dark current density values were achieved in the OPDs. This resulted in the best OPD performance with a promising responsivity of 0.42 A/W and specific detectivity of 2.6 × 10¹³ Jones at -2 V under near-infrared irradiation (810 nm). In addition, they exhibited excellent performance with a rising response time of 3-4 µs, falling response time of 6-11 µs, and -3 dB cut-off frequency of 80-100 kHz. Finally, the OPD is integrated into an organic thin-film transistor array to build a FoD sensor with 80 × 80 µm² pixels, resulting in the successful acquisition of a digital fingerprint image.