Efficient Thin Polymer Solar Cells with Post-Annealing

摘要

The development of high-performance organic solar cells with low-cost fabrication processes has become one of the most important tasks in the vast endeavors of releasing the world-wide energy demand from fossil fuels. Nowadays, the power-conversion efficiency of polymer solar cells in excess of 5% has been demonstrated, but they involve complicated film formation mechanisms of thick active layers or delicate design of spacer layers. These approaches, therefore, may increase the series resistance of the devices and complicate fabrication procedure. In this report, we present a highly efficient polymer solar cells with a bulk heterojunction layer of poly(3-hexylthiophene):[6,6]-phenyl-C_(61)-butyric acid methylester (P3HT:PCBM) which is annealed at 130°C for 5 min. in a nitrogen environment (O_2 < 0.1 ppm and H_2O < 0.1 ppm) before cathode deposition. The annealing temperature is much lower and the annealing time is shorter than previous works. The device exhibits conversion efficiency of 4.9%, fill factor of 53 %, and open-circuit voltage of 0.67 V. These values are still comparable with the highest values reported previously. The annealing process is expected to modify the network morphology of the P3HT:PCBM layer. Finally, the thickness of the active layer is reduced to 50 nm which is much thinner than previously reported values, may facilitating the fabrication of tandem photovoltaic structures.