Novel a-Si solar cells with delta-doped(${delta}x$-doped) P-layer have been fabricated to enhance the hole concentration of the P-layers. The ${delta}-$doped P-layer consists of very thin B sheets of 0.1-0.5 atomic layers and undoped a-SiC multi-layers. B-layers were prepared by photo-CVD and pyrolysis technique. The structural, optical and electrical characteristics of the delta-doped P-layer films were evaluated by means of FTIR, AES and SIMS. As the results of this study, it was found that the ${delta}$-doped P-layer showed much superior optical and electrical characteristics than those of conventional uniformly B-doped a-Si layers. 12.5% energy conversion efficiency was achieved for the Cell with ${delta}$-doped P-layer.