The correlation between the growth conditions, mechanism, microstructure and physical properties of n-type conductivity of carbon thin films are not yet fully understood. We therefore performed a systematic study of growing phosphorus (P)-doped hydrogenated amorphous carbon (n-C:H) films by PECVD from hydrocarbons using solid phosphorus target as a dopant precursor. The changes in the microstructure and physical properties of n-C:H films grown from a radio frequency (r.f.) discharge in methane gas as a function of r.f. power (P-rf) has been determined. Microstructure properties of the n-C:H films are studied, and their influence on the electronic properties is analyzed. It is shown that Prf plays a major role in the deposition of n-C:H films with influenced the H and P content and the proportion of sp(2)-C atoms. Moreover, the fabricated n-C:H/p-Si heterojunction solar cell, when exposed to AM 1.5 illumination condition (100 mW/cm(2), 25 degrees C), is also studied. The maximum of open circuit voltage (V-sc) and short circuit current density (J(sc)) for the cells are observed to be approximately 236 V and 7.34 mA/cm(2), respectively, for the n-C:H/p-Si cell grown at lower P-rf of 100 W. We have observed that the rectifying nature of the heterejunction structures is due to the nature of n-C:H films. (c) 2004 Elsevier B.V All rights reserved.