Effects of thermal annealing on the efficiency of bulk-heterojunction organic photovoltaic devices

This paper studies the effect of the annealing process on the performance of P3HT/PCBM photovoltaic devices, in terms of their efficiencies. The basic photovoltaic devices are annealed on a hot-plate, at a temperature of 150 °C for 10 min in air. For comparison, the thermal annealing of photovoltaic devices is carried out using rapid thermal annealing (RTA) equipment, at a temperature of 150 °C for 10 min in different environments such as in vacuum, in nitrogen and in argon, individually. The light conversion efficiency (E_ff) of the resulting photovoltaic devices increases from 2.29% (hot-plate annealing) to 2.77% after annealing in a vacuum environment. As a result, the organic photovoltaic devices, annealed in a vacuum show enhanced efficiencies compared with those annealed in different gas environments.