Near-Infrared Dye Engineering in Floating Gate Phototransistor Memory for Broadband Light Response

High Resolution Image Download MS PowerPoint Slide With increasing attention to optically responsive memory devices, phototransistor memory has been developed to span multiple spectral ranges by integrating optical programming capabilities. Owing to their deep penetration, low scattering, and low energy consumption, near-infrared (NIR) phototransistor memory possess greater potential for advanced applications compared to conventional organic transistor memories. In this study, two NIR dyes─bis[4,4′-dimethoxy(dithiobenzil)] nickel(II) (Ni(II)-DMDB) and N, N, N ′, N ′-tetrakis(4-dibutylaminophenyl)-1,4-benzoquinone diiminium bis(hexafluoroantimonate) ((DBA-BQDI) 2 (SbF 6 ) 2 )─are blended with an insulating and narrow bandgap poly(9-anthracenylmethyl methacrylate) (PAMA) to form the floating gate dielectrics, which is combined with a pentacene channel layer to fabricate phototransistor memory devices for investigating the influence of energy-level alignment on photoresponse and charge storage behaviors. In addition, the NIR dye systems are compared with a visible-light dye, 9,10-bis{2-[tris(1-methylethyl)silyl]ethynyl}anthracene (TIPS-3), and a wide-bandgap polystyrene. Despite both dyes exhibiting narrow bandgaps, (DBA-BQDI) 2 (SbF 6 ) 2 suffers from hole-transfer issues due to an energy-level mismatch, leading to device failure, whereas Ni(II)-DMDB possesses favorable energy-level alignment with the channel and PAMA, facilitating efficient electron trapping and enhancing memory performance. Consequently, illumination with visible (400–700 nm) and NIR-I light (700–950 nm) sources produces a measurable photoresponse and memory effect in the Ni(II)-DMDB system. Although NIR dyes can absorb NIR-II light (1000–1700 nm), their excessively narrow bandgap leads to severe nonradiative recombination, thereby hindering effective charge separation. Under illumination at 530 and 740 nm, the Ni(II)-DMDB system exhibits a memory ratio of 10 3 –10 4 with reliable long-term and endurance stability. In contrast, the visible-light dye TIPS-3 exhibits significantly inferior charge-storage performance due to its energy level being too closely aligned with that of the channel layer. This study demonstrates that by optimizing energy levels, NIR dyes can be effectively integrated into multiband photomemory devices, enabling the potential convergence of optical sensing and data storage.