Single-Component Photomultiplication-Type Photodetector Based on Donor–Acceptor Copolymer with Bias-Tunable Broadband to Narrowband Response

All-polymer photodetectors, owing to their remarkable advantages of flexibility and mechanical durability, exhibit demonstrated potential for application in the field of wearable technology. Nevertheless, the frequently employed double-component active layer structure is susceptible to performance degradation during long-term use. Consequently, a copolymer PM6-co-TTY6 possessing both donor and acceptor properties was designed and synthesized. The single-component active layer devices based on PM6-co-TTY6 exhibit pronounced photomultiplication characteristics. The maximum external quantum efficiency (EQEmax) of PM6-co-TTY6 device with thin active layer reaches 365% or 336% under a bias voltage of +5 V or −5 V, respectively. Remarkably, the device shows bias-tunable spectral response with increasing active layer thickness: a narrowband response (800–900 nm) with a EQEmax of 25% and a narrow full width at half maximum (FWHM) of 30 nm under negative bias, while a broadband response (300–900 nm) under positive bias. At this stage, the device can be switched between broadband and narrowband detection modes by reversing the polarity of the applied bias.