Amorphous silicon and carbon nanotube-based photovoltaics
Nguyen, Justin J.
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In this study, the possibilities of creating an effective amorphous silicon (a-Si) based photovoltaic (PV) cell supported by a 3D carbon nanotube (CNT) structure are investigated. Vertically aligned carbon nanotubes (VACNTs) provide a significant advantage increasing photon dwell time in photovoltaic materials via light trapping at off-normal angles to the sun. By creating a 3D array, CNTs allow for the use of less and therefore cheaper PV material, particularly a-Si. This study examines and presents the creation of such a novel PV cell through thermally-enhanced chemical vapor deposition (TECVD) and plasma-enhanced chemical vapor deposition (PECVD) techniques. The 3D a-Si PV cell that is presented consists of a single junction p-i-n photodiode less than 350 nm in total width that absorbs photons just above the 1.7 eV energy level. A close examination of the growth and morphology of a-Si and nanocrystalline silicon (nc-Si) thin films on CNTs is also presented and studied, with discussion stemming from the results of scanning electron microscopy (SEM), optical microscopy, atomic force microscopy (AFM), Raman spectroscopy, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV-Vis spectrophotometry, and current-voltage measurements.