This article shows the characteristics of pin-type a-Si:H thin-film solar cells with various PH3 concentrations in the i-layer. A series of phosphorus doped a-Si:H films were fabricated by mixing PH3 and SiH4 with H-2 during the i-layer deposition. The concentration of PH3 was varied in the range of 0-3650ppm. By phosphorus doping of the i-layer, the properties of the i-layer were changed light doped n layer (n-), and we were able to improve all these electrical parameters (V-oc, J(sc), and FF). Consequently, we achieved a higher conversion efficiency than in conventional pin-type a-Si:H solar cells with undoped i-layer.