Temperature dependence of polymer/fullerene organic solar cells

The temperature dependence of bulk heterojunction organic solar cells fabricated from poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) was studied in detail. Individual materials as well as blends and solar cell devices were examined. Light absorption, photoluminescence, quantum efficiency, total efficiency, and current-voltage characteristics were studied from temperatures −10 to 140 °C. A method and apparatus for testing these parameters at various temperatures is described. Parameters were measured for both unannealed and annealed samples to give insight into the annealing process. It was found that absorption and photoluminescence of devices shift both position and intensity with varying temperatures. Quantum efficiency and total efficiency were monitored as they increased with annealing. Once annealed, device efficiency peaked at temperatures from 10 to 60 °C because of competing temperature dependent effects of the materials. The temperature dependence study provides valuable information on device properties and thermal annealing.