Organic Liquid Crystals on Lewis‐Acid Monopolar Polymer for Room‐to‐Low‐Temperature High‐Performance Phototransistors

Organic phototransistors have garnered considerable attention for their potential in diverse optoelectronic applications. However, their inferior photoresponse or even out of operation at low temperatures severely limits their applications in extreme environments. In this work, high-performance organic phototransistors that operate from room temperature down to cryogenic conditions are demonstrated, utilizing smectic E (SmE) phase liquid crystals on a Lewis-acid monopolar polymer. These devices achieve a remarkable average responsivity of 417 ± 180 A W^-1 and an outstanding photosensitivity above 10⁴ even at 80 K. This superior photoelectrical performance stems from the efficient vertical exciton diffusion through the SmE liquid crystal, combined with effective exciton dissociation and stable electron trapping at the polymer interface across the operating temperature range. Furthermore, the devices exhibit reliable photoinduced memory behavior, featuring stable storage-erase cycles and long retention time across a wide temperature range, highlighting their potential for optical memory applications. The results demonstrate that liquid crystals are promising candidates for room-to-low-temperature high-performance phototransistors, paving the way for advanced optoelectronic applications in harsh environments.