High-performance organic photorefractive materials containing 2-ethylhexyl plasticized poly(triarylamine)

We have developed high-performance photorefractive (PR) materials containing ternary composites of 2-ethylhexyl plasticized poly(triarylamine) (PTAA), a chromophore, and a photosensitizer. PTAAs containing carbazole or fluorene in a main chain and 2-ethylhexyl in a side chain are synthesized via palladium-complex catalyzed polyamination. The spectroscopic, thermal, and hole-transport properties of these polymers are analysed. The carbazole-containing polymer shows good compatibility with chromophores, affording the high chromophore loading of polymer/chromophore = 70/30 wt%. This polymer can be utlilised in PR devices as a host material without any additional plasticizer. The PR performance of a polymer/chromophre/sensitizer (69/30/1 wt%) composite was evaluated using an optical four-wave mixing technique (FWM) to determine the change in refractive index Δ n and the average-response time constant τ . This composite exhibits results comparable to the inorganic crystals BSO or SPS when the optical sensitivity is maximized at 15.8 cm 3 kJ −1 , with Δ n = 5.3 × 10 −4 and τ = 2 milliseconds under a pump-laser intensity of 149 mW cm −2 . This is one of the highest values obtained for an organic PR composite with a pump laser operating at 633 nm. We report high-performance photorefractive materials containing poly(triarylamine), chromophore, and photosensitizer, exhibiting optical sensitivity 15.8 cm 3 kJ −1 with 2 ms response-time.