(87c) Three Dimensionally Structured Electrodeposited CdS/CdTe Solar Cells

Three dimensionally structured thin film photovoltaic devices based on interdigitated arrays of microscale electrodes are examined by electrodeposited CdS/CdTe heterojunctions and supported with EQE simulations, indicating considerable J_SC enhancement is possible through elimination of the front contact and window layer required in planar geometry devices.  Electrode parameters including, pitch, width, height, and material are modeled and experimentally probed, demonstrating experimentally and capturing in models dependence on intrinsic material properties and electrode dimensions.  In contrast to analogous silicon wafer back contact solar cells where the electrodes are placed on the silicon absorber at the end of processing, in this design the semiconductor is deposited on the electrodes, taking advantage of the thin film processing already required.  CdS/CdTe thin film and three dimensionally structured heterojunction devices are electrodeposited from aqueous solutions with CdTe grain size and stress displaying strong dependence on [Cd²⁺]. Typical annealing temperatures required for absorber optimization in thin films allow for only limited improvement in back contacted devices due to Schottky barrier formation on the nonoptimal electrode materials.  Electrodeposited contact materials, ZnO and SbTe, are also examined and show promise of reduced reactivity and improved performance.