Organic-inorganic composites for solar cells

Abstract

As the search for alternative sources of energy other than fossil fuels continues to expand, photovoltaic technology (direct conversion of solar energy into electrical energy) has been identified as one of the promising technologies. Solar cells based on blends of conjugated polymers and fullerene derivatives have recently attracted significant attention due to their great promise for the realization of printable, portable, flexible, and low-cost renewable energy sources. However, it is not easy to precisely control the nanoscale morphology of photoactive layer which seriously affects the carrier transport. In addition, control of the charge transport at organic-electrode or organic-inorganic interface is also challenging in organic-based solar cells. Quality of the electrode interface is also critical for the device stability. Development of the organic-inorganic composites for solar cells offers an alternative way to realize high performance and low cost solar cells. This chapter introduces the organic-ZnO nanorod composite solar cells. The environmentally friendly ZnO nanorod arrays can be grown in an aqueous solution with vertical alignment and small rod-to-rod spacing. This provides a solution-based route to the fabrication of low-cost organic-inorganic photovoltaic devices with highly oriented ZnO nanorod arrays. In order to achieve better exciton dissociation and charge transport, three types of interfacial modifications are demonstrated here. The addition of PCBM (6, 6-phenyl-C61-butyric acid methyl ester) clusters can enhance the phase separation and optical absorption. Inserting TiO2 nanoparticles leads to a formation of double heterojunction, providing efficient exciton dissociation and charge transfer. The insertion of V2O5 nanopowder can suppress the leakage current and enhance the absorption. With the PCBM clusters, TiO2 nanoparticles, or V2O5 nanopowder, their power conversion efficiencies can be significantly improved. Furthermore, these interfacial modifications are all fabricated by solution approaches. Compared to the vacuum-deposited techniques, these approaches are simple, expeditious, and effective. They are also advantageous for potential applications to mass production of various large-area printed electronics and photonics with a very low cost. ? 2012 by Nova Science Publishers, Inc.