NOVELTY - A thin-film photovoltaic conversion device (1), comprises a substrate (2); a first electrode (3); a n-type layer (5); a graded band gap layer (6); a p-type layer (7); and a second electrode (8) in sequential manner. The graded band gap layer includes pure silicon and silicon in chemical compositions with germanium, carbon, nitrogen, or nitrogen and oxygen. The substrate is made of metal, glass, or plastic. The graded band gap layer mainly comprises silicon.    USE - As a thin-film photovoltaic conversion device useful in solar cell, crystalline silicon thin film solar cell, tandem (hybrid)-type thin film solar cell useful for conversion of solar energy into electric power.    ADVANTAGE - The photovoltaic conversion device allows to set up the production of semi-conductors, where instead of i-layers, there is formed one layer of a complex smoothly changeable structure SixGe1-x-Si-SixCy-SixNy-SixOyNz. Thus, the band gap layer size is essentially changed, and it absorbs the solar spectrum much better, which, in its turn, enables an increase of solar energy conversion to eta of approximately 12%. The method provides the performance of a conversion device, reduces its cost, enhances the flexibility of manufacturing steps, and improves manufacturing efficiency.    DETAILED DESCRIPTION - A thin-film photovoltaic conversion device (1), comprises a substrate (2); a first conductive layer (3); a first doped layer (5); a graded band gap layer (6); a second doped layer (7); and a second conductive layer (8) in sequential manner. The graded band gap layer has a first side face and a second side face, and includes pure silicon and silicon in chemical compositions with germanium, carbon, nitrogen, or nitrogen and oxygen, of the formula selected from SixGe1-x, SixCy, SixNy, and SixOyN2, where chemical compositions are simultaneously comprised in the band gap layer and disposed successively, and smoothly transitioning, in a direction from the first side face to the second side face. The substrate is made of metal, glass, or plastic (preferably flexible plastic). The graded band gap layer mainly comprises silicon. The device further comprises a reflective layer; an anti-reflective layer (9); and a protective laminating layer (10) in sequential manner. The first conductive layer and second conductive layer are electrodes. The doped layers are disposed on both side faces of graded band gap layer, where one doped layer is a p-type layer and another doped layer is an n-type layer. The energetic limits of chemical compositions, comprised in band gap layer, change from 0.9-3.5 eV. The first doped layer, graded band gap layer, and second doped layer are forms using chemical vapor deposition, low-pressure chemical-vapor deposition, plasma-enhanced chemical-vapor deposition, high-frequency plasma-enhanced chemical-vapor deposition, very-high-frequency plasma-enhanced chemical-vapor deposition, or hot-wire chemical-vapor deposition. An INDEPENDENT CLAIM is included for manufacturing a thin-film photovoltaic conversion device, involving forming first conductive layer, a first doped layer, a graded band gap layer, second doped layer, and second conductive layer sequentially on a substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-section of the thin-film photovoltaic conversion device.    Thin-film photovoltaic conversion device (1)    Substrate (2)    First conductive layer (3)    First doped layer (5)    Graded band gap layer (6)    Second doped layer (7)    Second conductive layer (8)    Anti-reflective layer (9)    Protective laminating layer. (10)