Highly conductive boron-doped hydrogenated microcrystalline silicon (μc-Si: H) films and solar cells are pre- pared by plasma enhanced chemical vapour deposition (PECVD). The effects of diborane concentration, thickness and substrate temperature on the growth and properties of B-doped layers and the performance of solar cells with high deposited rate i-layers are investigated. With the optimum p-layer deposition parameters, a higher efficiency of 5.5% is obtained with 0.78nm/s deposited i-layers. In addition, the carriers transport mechanism of p-type μc-Si: H films is discussed.