Influence of the sensitizer reduction potential on the sensitivity of photorefractive polymer compositesElectronic supplementary information (ESI) available: Determination of τ50 and E(ηmax) from measured data, comparison of pre-illuminated and non pre-illuminated data transients and the ratio of their respective sensitivities. See DOI: 10.1039/c0jm01208d

We report on a series of near infrared (NIR)-sensitive photorefractive polymer composites (PPCs) based on the hole-conducting polymer PF6-TPD, which are sensitized by soluble fullerene-derivatives as electron-accepting agents. We demonstrate a direct correlation between the electron accepting capability of the sensitizer and the holographic response time. The holographic recording speed is found to improve by one order of magnitude when lowering the reduction potential of the sensitizer by approx. 400 mV, while all other physical parameters of the materials remain essentially identical. Furthermore, the lifetime of the mobile charge carriers is found to correlate linearly with the reduction potential, thus indicating a decrease in recombination rates for stronger accepting capability of the sensitizer. Finally, we found that pre-illumination enhanced the holographic sensitivity. The effect is found to be most pronounced for the strongest acceptor due to reduced recombination of the preformed carriers. Overall, the PPCs reported here feature the currently highest sensitivity in the NIR spectral region. We demonstrate a direct correlation between the electron accepting capability of the sensitizer and the holographic response time of a series of near infrared-sensitive photorefractive polymer composites.