Weng, Yi-HsunYi-HsunWengChen, Wei-ChengWei-ChengChenLu, Chen-HanChen-HanLuHsu, Chih-WeiChih-WeiHsuErcan, EnderEnderErcanCHUNG-CHIH WUCHENG-LIANG LIULin, Yan-ChengYan-ChengLinChen, Wen-ChangWen-ChangChen2025-08-282025-08-282025-09https://www.scopus.com/record/display.uri?eid=2-s2.0-105011539095&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/731699Organic semiconductors with low dielectric constants and large exciton binding energies are limited in their photoelectrical applications compared to inorganic semiconductors. By introducing polar conjugated molecules that form an interfacial dipole with the channel, a highly photoresponsive phototransistor can be achieved. In this work, we utilize a series of three-carbazole-armed molecules as the molecule electret, including 1,3,5-tris(3-(carbazol-9-yl)phenyl)-benzene (TCPB), 2,4,6-tris(3-(carbazol-9-yl)phenyl)-pyridine (TCPY), 2,4,6-tris(3-(carbazol-9-yl)phenyl)-pyrimidine (TCPM), 2,4,6-tris(3-(carbazol-9-yl)phenyl)-triazine (TCPZ). The dipole moments of these molecules are affected by the polarity of their heterocyclic cores, the dihedral angles between conjugated moieties to form a twisted intramolecular charge transfer, and isomeric configurations. Phototransistor memory devices with highly polar molecules TCPY and TCPM as electrets exhibit a superior threshold voltage of the photowriting state (Vth, PW) and sensitivity (P) compared to their less polar counterparts, TCPB and TCPZ. These device parameters represent the charge traps created during photowriting processes. Furthermore, the Vth, PW and P are enhanced when the electret thickness increases. These observations suggest that the strong interfacial dipole formed by polar molecules facilitates exciton dissociation and charge trapping. Further discoveries reveal that the photoresponse rate of the memory is inversely correlated to the exciton lifetime of the molecules, which suggests that exciton diffusion plays an essential role in the device's photoresponse. The strategy of introducing polar electrets with interfacial dipoles can be effectively performed in phototransistor memory, inspiring new organic semiconductor designs for developing high-performance phototransistors.falseCarbazolesElectretExciton binding energyInterfacial dipolePhototransistor[SDGs]SDG7journal article10.1016/j.mtchem.2025.1029002-s2.0-105011539095