We report on the growth of highly conducting p-pc-Si:H films by hot-wire CVD. A systematic variation of the doping gas (trimethylboron) ratio was first carried out. High dark conductivity, sigma (D) approximate to 1.0 Ohm (-1) cm(-1) and low activation energy of dark conductivity, E(a)approximate to 62 meV have been achieved for thick films. For thin films (d approximate to 20 nm), sigma (D)approximate to4.7X10(-2) Ohm (-1) cm(-1) and E(a)approximate to 80 meV were obtained. The annealing characteristics of thick films show thermally assisted dopant activation. Microcrystalline growth in these films was verified by XRD. A very thin p-a-Si:H seed layer (d approximate to2 nm) was grown for preparation on TCO-coated substrates prior to the deposition of the p-muc-Si:H layer. The incorporation of a p-muc-Si:H layer into a-Si:H p-i-n solar cells has improved the open circuit voltage (870-900 mV) relative to the use of a p-a-SiC:H layers. At present the best I-V parameters for p-i-n and muc-Si/c-Si heterjunction solar cells are J(sc)=12.3 mA cm(-2), V-oc=873 mV, FF=72%, eta =7.8% and J(sc=)26.6 mA cm(-2), V-oc=532 mV, FF=74%, and eta =10.6%, respectively. To the best of our knowledge, these are the first heterojunction solar cells with the p-muc-Si:H emitter grown by HWCVD. The necessity of a seed layer has been found to be very much important in both types of solar cells. Two different types of seed layers, and their thickness variation, were also investigated.