Photorefractive effect in triphenylamine-based monolithic molecular glasses with low Tg

A novel series of triphenylamine-based photorefractive molecules M1–M5 with the different push-pull structures were designed and prepared. These molecules can form stable glasses with low glass transition temperature and their optical absorptions as well as photoconductivities at 633 nm increase systematically with increasing acceptor strength and conjugation length. As an unambiguous evidence, the two-beam-coupling experiment was performed to prove the photorefractive effect in each compound with or without an additional sensitizer. Obvious two-beam-coupling effects were obtained for the molecules with good film-forming ability and long-term stability, and among them single-component M1 which has a highly asymmetric structure using both a nitrobenzene and a cyano group as the acceptor showed the best PR performance with a gain coefficient of 52 cm−1 at 0 V μm−1 and 165 cm−1 at 40 V μm−1. Fast response time of 0.025–0.23 s were also obtained at low electric field for these glasses. The correlation of the molecular structure with the PR property was discussed, and a possible explanation for the unique energy transfer observed in M1 and M2 under zero field was proposed.

Research highlights▶ A series of triphenylamine-based molecular glasses with low Tg and long-term stability were designed and prepared via simple reactions. ▶ Single-component M1 exhibited the better PR performance with a gain coefficient of 52 cm−1 (0 V μm−1) and 165 cm−1 (40 V μm−1). Fast response time of 0.025–0.23 s were obtained at low electric field for these glasses. ▶ The overall performances suggest that the present triphenylamine-based molecules are potentially good candidates for commercial application in organic photorefractive devices.