Device Characteristics of Bulk-Heterojunction Polymer Solar Cells

Device characteristics under dark and illumination

Polymer solar cells are important candidates for sustainable, low-cost energy generation. Frequently, the active layers of these devices are comprised of two organic semiconductor constituents that are chemically incompatible. The tendency for one of the constituents to preferentially segregate to the surface of thin films results in compositional heterogeneities along the film depth. This work explores the impact of vertical compositional heterogeneities on charge transport in polymer solar cells via modular construction of devices. By investigating a series of solar cells with identical device architectures, but with interfacial segregations that are reversed in the active layers, Kahn and Loo et al. [1] found that the device performance of bulk-heterojunction polymer solar cells is, in fact, independent of interfacial segregation of active layers, contrary to a widespread assumption.

Acknowledgment:  Funding from ONR (N00014-08-1-1175), SOLAR Initiative (DMR-1035217) and MRSEC program (DMR-0819860) at the NSF. A.K. also acknowledges support from DOE (DEFG02-04ER46165 and DE-S0001084).