Nano-Structured and Micro-Structured Semiconductors for Higher Efficiency Solar Cells

Hybrid thin-film solar cells are fabricated on the glass substrate using ZnO nanorods, well-aligned single-crystalline Si nanowires (SiNWs), and poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) as well as micro-structured III-V semiconductors . The effect of introducing a solution-processed fullerene as an electron transport layer on the polymer/ZnO nanorod array composite solar cells is investigated . Devices with the fullerene layer exhibit a larger short circuit current density (10.16 mA/cm²) than those without this layer (9.37 mA/cm²). For the Si NWs with P3HT:PCBM, the well-aligned SiNWs are fabricated from Si wafer and transferred onto the glass substrate with the P3HT:PCBM. Such SiNWs provide uninterrupted conduction paths for electron transport, enhancing the optical absorption to serve as an absorber, and increase the surface area for exciton dissociation . Our investigations show that Si NWs are promising for hybrid organic photovoltaic cells with improved performance by increasing the short-circuit current density from 7.17 to 11.61 mA/cm². III-V semiconductors are also used for thin-film solar cells. InGaP/GaAs two-junction square-based (25 mum times25 mum) cuboid arrays with a height of 6.52 mum were released from GaAs substrates by the epitaxial lift-off process. These InGaP/GaAs cuboid arrays were transplanted to the P3HT film spun on ITO glass substrate. In addition to the significant cost reduction, our method shows the rapid transplantation and the potential for high-efficiency large-area devices fabrication.