High-efficiency large area flexible organic solar cells

We report on the realization of high-efficiency bulk heterojunction PV devices based on P3HT/PCBM on transparent plastic substrates, from one elementary cell to large area modules, and we compare with results obtained on glass. The first target consists in the optimisation of the processing parameters in order to obtain the highest possible Power Conversion Efficiency (PCE) values for individual cells. We have reached PCE close to 4% with small dispersion on plastic substrates for cells of 0.28 cm² active area, compared to 5% on glass. Modules of multiple cells are then elaborated on 5x5 cm substrates with a design aimed to minimize ohmic losses, and interconnection resistances. For glass module, with 12 individual cells on a 5x5 cm² substrate we obtain PCE of 3.26 % (12.4 cm² active surface). Larger modules with active area up to 35 cm² exhibiting PCE of 2.8 % and open circuit voltage higher than 6V are also demonstrated for glass, approaching the requirements for commercial electronic applications. On PET, record efficiency of 2.85 % is obtained for a 8.8 cm² module and PCE of 2.52 % is demonstrated for a large area module with 53 cm² active surface. The influence of the geometric parameters of the individual cells and their type of connection (parallel or series) on the module characteristics is also discussed.