IRG-B: Wrinkles and Folds as Photonic Structures in Photovoltaics

1. IRG-B: Wrinkles and Folds as Photonic Structures in Photovoltaics NaiPhuanOng, Princeton University, DMR 0819860 J. Kim1, P. Kim2, N. Pegard3, S. J. Oh4, C. R. Kagan4, J. Fleischer3, H. A. Stone2 and Y.-L. Loo1 1Department of Chemical and Biological Engineering, 2Department of Mechanical and Aerospace Engineering, 3Department of Electrical Engineering, Princeton University 4Department of Materials Science and Engineering, University of Pennsylvania We exploit the elastic instabilities of polymer surfaces under compressive mechanical stress to generate wrinkles and deep folds with prescribed dimensions and at pre-specified coverage over large areas. These wrinkles and deep folds act as photonic structures; they increase light coupling into and trapping within polymer photovoltaics that are subsequently constructed atop such surface structures. Devices on surfaces comprising wrinkles and folds exhibit a 79% increase in the external quantum efficiency (EQE) in the visible compared to analogous devices constructed on flat surfaces. More significantly, we observe an exponential increase in near-infrared light absorption in these devices. While we demonstrate this concept with polymer photovoltaics, the controlled introduction of compressive stress provides a straightforward and economical route to large-scale patterning of photonic structures for flexible opto-electronics. Reference: J. Kim et al., Nature Photonics, in press 2012; doi: 10.1038/nphoton.2012.70 Acknowledgment: We are grateful for funding from the ONR (N00014-11-10328) and the NSF’s SOLAR Initiative (DMR-1035217) and MRSEC program (DMR-0819860).