A tandem thin film solar cell with a nanoplate absorber bottom cell that can solve the trade-off between light absorption and carrier transport in thin film solar cell is investigated. This structure has an n-type microcrystalline silicon nanoplate array on the substrate, and the p- and i-layers are sequentially grown along the surface of each n-type microcrystalline silicon nanoplate for bottom cell. After above bottom cell is fabricated, a similar process is used to fabricate an amorphous Si p-i-n top cell. High-aspect-ratio width/height nanoplates allow for the use of a material with sufficient thickness to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers perpendicular to light absorption. The power conversion efficiency of nanoplate solar cells with 15,000 nm plate height is around 10%, which is an approximately 40% enhancement over a planar solar cell with a similar layer stack. Crown Copyright (c) 2011 Published by Elsevier B.V. All rights reserved.