Advanced polycrystalline silicon thin film solar cells using high rate plasma enhanced chemical vapour deposited amorphous silicon on textured glass

摘要

Solid phase crystallized polycrystalline silicon (poly-Si) thin-film solar cell on glass is an emerging Photovoltaics (PV) technology combining the robustness of crystalline Si material with advantages of the thin-film approach. The main goals for this technology to successfully compete with others are 1) to significantly increase the cell efficiency; 2) to increase production throughout to lower the manufacturing cost. The work in this thesis is focused on reaching in two aspects: 1) enhance the optical absorption by optimizing the aluminum (Al) induced textured (AIT) glass and developing a front glass antireflective (AR) layer for thin film poly-Si solar cell, and 2) explore the plasma enhanced vapour deposition (PECVD) process parameters space to significantly increase the deposition rate of a-Si:H suitable for the fabrication of solar cell grade SPC poly-Si films. As a result of the work on optical absorption enhancement, a 9.3% efficient UNSW standard rate PECVD poly-Si thin film solar cells with a short circuit current density (Jsc) of up to 29 mA/cm2 in 4.4 cm2 cell area was demonstrated on a more advanced AIT glass superstrates than previously. A reduction of about 3% in total reflectance was achieved on poly-Si thin film diodes by applying the optimal AR process. As a response to the low PECVD deposition rate (~25 nm/min), very high deposition rates (up to 265 nm/min for 13.56 MHz and 350 nm /min for 35 MHz radio frequency) were demonstrated by using a combination of high RF power, high total flow, high pressure and substrate temperature in a PECVD reactor. An individual chamber, with a wider electrode spacing, which is separate to the standard rate process was dedicated for this high rate deposition for the absorber layers within the poly-Si thin film cells. No deteriorations were observed in aspects of both crystal quality and electrical performance of the high rate absorber cells in comparing to a reference standard rate cell. The investigations in this thesis clearly show that both AIT glass and high rate PECVD are promising for poly-Si thin film solar cell on glass technology