IMEC Method Extends Lifetime of Organic Solar Cells

IMEC and its associated laboratory Institute for Materials Research in MicroElectronics reported they have improved the composition of organic solar cells. Researchers developed conjugated polymers to stabilize the nanomorphology of the active layer.

Staff -- Semiconductor International, 10/14/2008 9:03:00 AM

IMEC (Leuven, Belgium) said its associated laboratory Institute for Materials Research in MicroElectronics (IMOMEC, Diepenbeek, Belgium) has developed a method to stabilize organic solar cells, with an order of magnitude improvement in cell lifetimes.

The center, located on the campus of the Hasselt University, said the research paves the way for commercial organic solar cells with an operational lifetime of more than five years. The researchers optimized the nanomorphology of the active layer, creating a more stable mix of organic compounds that can trap photons and transport the light energy to an electrical contact.

Organic solar cells deteriorate as the compounds tend to separate into different phases, reducing conversion efficiency. IMEC has shown that this phase segregation is related to the mobility of the organic polymer, and that fixation of the nanomorphology of the polymers could improve lifetimes.

TEM results for polymer/PCBM 1:1 active layers after degradation at 100°C for two hours show phase segregation for the Rieke P3HT polymer (left), but a stable morphology for the novel conjugated polymer (right). (Source: IMEC)

IMEC/IMOMEC developed conjugated polymers to stabilize the nanomorphology of the active layer. Experiments on bulk heterojunction organic solar cells based on the material showed no degradation after >100 hours, whereas reference cells degraded after a few hours. The result, IMEC said, is a lifetime improvement of at least a factor of 10. The cells achieved efficiencies near 4%, with an expectation that efficiencies could be improved to >10%. Future research targets further refinement of the method by optimizing the chemical structures of the conjugated polymers, IMEC said.