Investigation of optimum conditions for high-efficiency organic thin-film solar cells based on polymer blends

Organic thin-film solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-buteric acid methyl ester (PCBM) blend system attracts most attention. We studied the effects of P3HT:PCBM blend composition and thermal annealing treatment on the device performance. P3HT:PCBM weight ratio mainly influenced short circuit current (JSC) and power conversion efficiency (PCE). For the cells with P3HT:PCBM ratio of 1:0.66 showed the maximum PCE of 1.4%. Thermal annealing improved the photovoltaic characteristics and we achieved PCE of 2.0% with the annealed device. Furthermore, we observed transient photocurrent responses of devices to solar simulated light (air mass 1.5 G, 100 mW/cm2) irradiation. Annealing treatment resulted in suppression of the decay of photocurrent, suggesting that carrier transport network was improved by thermal annealing.