NOVELTY - The method comprises preparing a substrate, depositing a back electrode on the substrate, forming an absorption precursor on the back electrode, forming an absorber layer over the absorbent precursor, forming a buffer layer over the absorbing layer, forming a window layer on the buffer layer, and forming a front electrode over the window layer. The substrate preparation step comprises cleaning the substrate for 9-11 minutes with acetone, then ultrasonically washing with methanol, and then washing with distilled water.    USE - The method is useful for manufacturing a thin film solar cell (claimed).    ADVANTAGE - The method is capable of time-efficiently and economically manufacturing the thin film solar cell with high production efficiency.    DETAILED DESCRIPTION - The method comprises preparing a substrate, depositing a back electrode on the substrate, forming an absorption precursor on the back electrode, forming an absorber layer over the absorbent precursor, forming a buffer layer over the absorbing layer, forming a window layer on the buffer layer, and forming a front electrode over the window layer. The substrate preparation step comprises cleaning the substrate for 9-11 minutes with acetone, then ultrasonically washing with methanol, and then washing with distilled water. The back electrode is deposited on the top of the substrate using a sputtering apparatus to a thickness of 0.5-1 mu m. The absorption precursor and the back electrode are laminated on the substrate by applying indium selenide metal powder on the substrate, and heating the substrate at 100-200 degrees C in a semiconductor heat treatment equipment. The absorption precursor is laminated on the substrate by heat-treating the substrate at 400-500 degrees C. The absorbing layer is formed on the substrate by coating cadmium sulfide on the substrate to a thickness of 50-70 nm. The buffer layer is deposited by coating 2 wt.% of zinc oxide of 250-300 nm thickness on the substrate, doping aluminum of 20-80 nm thickness after depositing the zinc oxide, and heating the substrate. The front electrode is formed using a screen-printing machine or electronic beam apparatus.