Study on the photoconductive properties of charge carriers in donor-acceptor copolymer P(EDOT-FL) and P(EDOT-FL):PCBM blend

- P(EDOT-FL):PCBM blend films were prepared at polymer to PCBM ratios of 1:0, 1:1 and 1:2.
- Incorporation of PCBM result in quenching of the fluorescence intensity and increased photoconductivity.
- Polymer showed positive solvatochromism.
- Achieved a photogeneration efficiency of 86% and photoconductive sensitivity of 5.44 × 10−7 SW−1cm at 70 V/μm.

The photoinduced charge transfer properties of low band gap donor-acceptor π-conjugated copolymer poly(2,5-(3,4-ethylenedioxythiophene)-alt-2,7-(9,9-dioctylfluorene)) labelled as P(EDOT-FL) has been investigated through solvatochromic and photoconductivity studies. The effect of strong acceptor, Phenyl-C61-butyric acid methyl ester (PCBM) on the photogeneration of free carriers is studied by comparing the fluorescence spectra and photoconductive properties of the polymer-PCBM blend [P(EDOT-FL):PCBM] films with the pristine polymer films. The positive solvatochromism exhibited by the P(EDOT-FL) revealed its photoinduced charge transfer nature of the absorption and emission bands. The blend films exhibited quenching of the fluorescence intensity and showed increased photoconductivity. Internal photocurrent efficiency and photoconductive sensitivity of the pristine P(EDOT-FL) films and P(EDOT-FL):PCBM blend films were calculated as a function of electric field, by measuring the photocurrent generated in the sample. Blend films exhibited higher internal photocurrent efficiency of 86% and photoconductive sensitivity of 5.44 × 10−7 SW−1cm at 70 V/μm. The obtained photoconductive sensitivity at low electric field (<10 V/μm) is sufficient for photorefractive applications.

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