Recent Progress in Amorphous Silicon Alloy Leading to 13% Stable Cell Efficiency

Significant progress has recently been made in amorphous silicon (A-Si) alloy solar cells using a spectral-splitting, triple-junction structure in which the bandgap of each component cell is designed to absorb a different portion of the solar spectrum. Key factors leading to the stable 13% active-area cell efficiency include: i) using a high hydrogen dilution technique during the growth of theintrinsic layers, ii) employing a bandgap profiling design for the a-SiGe alloy cells, iii) incorporating appropriate current mismatch for component cells, iv) developing microcrystalline dope layers for the tunnel junctions and the window layer, v) enhancing the light trapping effect of the textured back reflector, and vi) improving the performance of the top conducting oxide layer. Thesefactors along with other recent developments relevant to the achievement of high efficiency cells will be discussed.