We have developed a high-rate plasma process based on high-pressure and silane-depletion glow discharge for highly efficient microcrystalline silicon (ltc-Si:H) p-i-n junction solar cells. Under high-rate conditions (2-3 nm/s), we find that the deposition pressure becomes the dominant parameter in determining solar-cell performance. With increasing deposition pressure from 4 to 7-9 Torr, shortcircuit current increases by similar to 50% due to a remarkable improvement in quantum efficiencies at the visible and near infrared. As a result, the maximum efficiency of 9.13% has been achieved at an i-layer deposition rate of 2.3 nm/s. We attribute the improved performance of high-pressure-grown mu c-Si:H solar cells to the structural evolution toward denser grain arrangement that prevents postoxidation of grain boundaries. (c) 2006 Elsevier B.V. All rights reserved.