Highly transparent front electrodes with metal fingers for p-i-n thin-film silicon solar cells

摘要

The optical and electrical properties of transparent conductive oxides (TCOs), traditionally usedin thin-film silicon (TF-Si) solar cells as front-electrode materials, are interlinked, such that an increase inTCO transparency is generally achieved at the cost of reduced lateral conductance. Combining a highlytransparent TCO front electrode of moderate conductance with metal fingers to support charge collectionis a well-established technique in wafer-based technologies or for TF-Si solar cells in the substrate (n-i-p)configuration. Here, we extend this concept to TF-Si solar cells in the superstrate (p-i-n) configuration.The metal fingers are used in conjunction with a millimeter-scale textured foil, attached to the glass superstrate,which provides an antireflective and retroreflective effect; the latter effect mitigates the shadowinglosses induced by the metal fingers. As a result, a substantial increase in power conversion efficiency,from 8.7% to 9.1%, is achieved for 1-μm-thick microcrystalline silicon solar cells deposited on a highlytransparent thermally treated aluminum-doped zinc oxide layer combined with silver fingers, compared tocells deposited on a state-of-the-art zinc oxide layer.