An apparatus for the preparation of a photoelectric conversion layer for a photoelectromotive force member includes:(a) a film-forming chamber having an inner space in which a substrate holder for a substrate is provided;(b) an exhaust pipe connected to the film-forming chamber and through a main valve to an exhaust pump;(c) a concentric triplicate conduit connected through a nozzle to the film-forming chamber. The concentric triplicate conduit includes:(i) an outer passage for introducing a gaseous raw material and formed by a circumferential wall and an inner wall having a plurality of gas liberation holes;(ii) a middle passage for applying microwave energy to said raw material gas to generate an active species and having a mixing region at the downstream side before the nozzle means, and(iii) a central passage situated horizontally within said middle passage (ii) for introducing a gaseous precursor and for transporting the gaseous precursor toward the film-forming chamber and being open at its end positioned in the mixing region leaving a desired distance to the nozzle means; said middle passage (ii) being formed by the inner wall of the outer passage and a circumferential wall of the central psssage (iii).Also included are:(d) a feed pipe for introducing said raw material to said outer passage (i);(e) a microwave power source for generating said microwave energy; and(f) a feed pipe for introducing said gaseous precursor to said central passage (iii).