A study on stability of active layer of polymer solar cells: effect of UV–visible light with different conditions
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The objective of this study is to investigate the stability of the active layer of polymer solar cells from the effect of UV–visible light irradiation using different conditions with respect to time. The active layers were composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM), deposited on conductive glass substrates through spin coating. These samples are placed in a UV–visible light exposure chamber using different conditions (heat and water) over the specific periods of time. The samples are analyzed by UV–visible absorption spectroscopy, X-ray photoelectron spectroscopy and Fourier transforms infrared spectroscopy (FTIR) measurements. The results indicate that after continuous exposure to UV irradiation for 72 and 120 h, the sample shows a significant decrease in absorption of the main peak. The sample shows around 25% loss in absorption (main peak) after 72 h of irradiation. The FTIR results illustrate a progressive decrease in intensities of all typical absorption peaks owing to P3HT ring scission, side chain oxidation as well as degradation of the side groups of PCBM.