Boosting the Photoresponse of Transistor Memory through Triplet–Triplet Annihilation Upconversion Using Diphenylanthracene Copolymers

Delayed fluorescence presents considerable opportunities for improving the performance of optoelectronic devices; however, the utilization of triplet–triplet annihilation (TTA) upconversion in phototransistors has not been extensively investigated. This study addresses this gap by examining the impact of TTA on phototransistor memory using a blend of the upconversion copolymer poly(diphenylanthracene-co-methyl methacrylate) (PDPAMA) and platinum(II) octaethylporphyrin (PtOEP) as an electret. In this TTA process, PDPAMA acts as the emitter. At the same time, PtOEP serves as the sensitizer, efficiently absorbing longer-wavelength light and enabling the conversion of 530 nm green light into 440 nm blue delayed fluorescence. To harness this upconversion fluorescence, α-sexithiophene is employed as the semiconductor channel layer due to its broad absorption band, effectively capturing the emitted blue light. The presence and influence of the TTA process on photomemory devices are confirmed through comprehensive optical analyses. Devices incorporating PtOEP demonstrate superior memory effects under photoassisted electrical writing compared to those with only PDPAMA, highlighting the effectiveness of the TTA upconversion mechanism in boosting the device’s photoresponse. This research underscores the substantial potential of TTA upconversion for advancing phototransistor memory applications.