High-Efficiency Large-Area Carbon Nanotube-Silicon Solar Cells

Currently studied carbon nanotube-silicon (CNT-Si) solar cells are based on relatively small active areas (typically <0.15 cm(2)); increasing the active area generally leads to reduced power conversion efficiencies. This study reports CNT-Si solar cells with active areas of more than 2 cm(2) for single cells, yet still achieving cell efficiencies of about 10%, which is the first time for CNT-Si solar cells with an active area more than 1 cm(2) to reach the level for real applications. In this work, a controlled number of flattened highly conductive CNT strips is added, in simple arrangement, to form a CNT-Si solar cell with CNT strips in which the middle film makes heterojunctions with Si while the top strips act as self-similar top electrodes, like conventional metal grids. The CNT strips, directly condensed from as-grown CNT films, not only improve the CNT-Si junctions, but also enhance the conductivity of top electrodes without introducing contact barrier when the CNT strips are added onto the film. This property may facilitate the development of large-area high-performance CNT or graphene-Si solar cells.