The contribution of coumarin 6 in light harvesting and photocurrent of P3HT:PCBM bulk heterojunction solar cell

Coumarin 6 dye (C6) has been included into an active layer of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) bulk heterojunction solar cell. The amount of C6 in the active layer blends was varied, and the optical absorption and photocurrent of the devices were recorded. The optical absorption spectroscopy of the active layer blend films showed that the increase in C6 concentration in a blend increased the absorption peak value, and the thermal treatment upon a blend film broadened the absorption wavelength range. The latter occurred as a result of a large red shift of P3HT absorption peak and, at the same time, a small red shift of C6 absorption peak in the blend films. As a result of pronounced contribution of the dye in the light harvesting of the blend films after thermal annealing, the C6 dye showed eminent contribution in the photocurrent spectra, better than that of P3HT. In addition to the contribution of C6 in the light harvesting and photocurrent of the investigated solar cells, this study enabled us to get a better understanding of the performance of the most common binary P3HT:PCBM when a third material is included inside it.