New sp3-bonded polytypic forms of BN, namely, 6H-BN and 30H-BN were prepared by plasma-assisted chemical vapor deposition (CVD) with an excimer laser at 193 nm being irradiated on the growing film surface. Only the 6H-BN was formed by post-deposition laser irradiation (PDL) of sp2-bonded BN precursor films prepared by plain plasma assisted CVD. The PDL demonstrated direct photo-induced phase transformation from sp2-bonded BN into denser sp3-bonded BN here. The growth mechanism was discussed with regard to the "bond-strength initiative rule", according to which the local thermodynamics at very early stage of growth should favor the formation of the strongest bond available (e.g. sp2-hybridiz ed bonds in BN). P-type sp3-bonded BN/n-type Si heterodiode solar cell was fabricated by this method and proved to work efficiently.