Abstract: In this paper,the CuTSPc supramolecnlar films,whose monolayer thickness is only 6Å and CuTSPc L-B films with C₁₈ Hpid chain spacer were modified on p-Si (111) by Langmuir-Blodgett technique.The surface photovoltage spectra of both film systems were measured for the first time.And it was found that the surface photovoltaic effect of the film systems was the greatest when there was only one monolayer of CuTSPc molecules on p-Si (lll).The experiments indicated that only the CuTSPc molecules within one monolayer adjacent to the semiconductor make a key role in the lightinduced interfacial charge transfer.Finally,the charge transfer process was proved to be a direct injection mechanism other than indirect injection one.

Key words: surface photovoltage spectro scopy, Langmuir-Blogett film, light-induced interfacial charge transfer, copper tetrasulfonatophthalocyanine