Thin film solar cells for windows based on low cost solution process and fabrication method thereof

A method of preparing a thin film solar cell, wherein the method comprises

• (a) dissolving a metal precursor and an organic binder in a solvent to obtain a precursor paste,
• (b) coating the precursor paste on the transparent conducting substrate,
• (c) annealing the transparent conducting substrate coated with the precursor paste in air or an oxygen gas atmosphere to obtain a metal oxide thin film, and
• (d) annealing the metal oxide thin film in a sulfur gas, a selenium gas or a sulfur/selenium mixed gas atmosphere to obtain a sulfurized or selenized metal oxide thin film.

A method of preparing a thin film solar cell, wherein the method comprises

• (a) mixing a first metal precursor, a first organic binder, and a first water-soluble solvent to obtain a first paste,
• (b) mixing a second metal precursor, a second organic binder, and a second water-soluble solvent to obtain a second paste,
• (c) coating the first paste on the conducting substrate to form a first paste layer,
• (d) coating the second paste on the first paste layer to form a second paste layer,
• (e) annealing the coated conducting substrate in air or an oxygen atmosphere to obtain a mixed oxide thin film, and
• (f) annealing the mixed oxide thin film in a sulfur gas, a selenium gas or a sulfur/selenium mixed gas atmosphere to obtain a sulfide or selenide thin film,
• wherein the first metal precursor and the second metal precursor are identical to or different from each other and are each independently a precursor of one or more Group IB metals, a precursor of one or more Group IIIA metals, or a mixture thereof;
• and the precursor of one or more Group IB metals and the precursor of one or more Group IIIA metals are each independently included in either the first metal precursor or the second metal precursor or both of them.

A method of preparing a thin film solar cell, wherein the method comprises

• (a) mixing first metal precursors, a first organic binder, and a first water-soluble solvent to obtain a first paste,
• (b) mixing second metal precursors, a second organic binder, and a second water-soluble solvent to obtain a second paste,
• (c) coating the first paste on the conducting substrate to form a first paste layer,
• (d) coating the second paste on the first paste layer to form a second paste layer,
• (e) annealing the coated conducting substrate in air or an oxygen atmosphere to obtain a CIG mixed oxide thin film, and
• (f) annealing the CIG mixed oxide thin film in a sulfur gas, a selenium gas or a sulfur/selenium mixed gas atmosphere to obtain a CIGS thin film,
• wherein the first metal precursors and the second metal precursors are identical to or different from each other and are each independently two or more kinds of precursors selected from Cu, In and Ga precursors;
• and the Cu, In and Ga precursors are each independently included in either the first metal precursors or the second metal precursors or both of them.

A method for controlling the band-gap of a photoactive layer of a thin film solar cell,

• wherein the thin film solar cell comprises (a) a transparent conducting substrate, (b) an absorber layer formed on the transparent conducting substrate, and (c) a buffer layer formed on the absorber layer, (d) a window layer disposed on the buffer layer, and (e) an electrode disposed on the window layer;
• the absorber layer is formed by a solution method;
• and
• the absorber layer is composed of CuInxGa(1-x)SySe(2-y) (where x is a real number of 0 to 1 and y is a real number of 0 to 2),
• the method comprising varying the ratio of In/Ga in the absorber layer to control the band-gap.

A method for controlling the transmittance of a photoactive layer of a thin film solar cell,

• wherein the thin film solar cell comprises (a) a transparent conducting substrate, (b) an absorber layer formed on the transparent conducting substrate, and (c) a buffer layer formed on the absorber layer, (d) a window layer disposed on the buffer layer, and (e) an electrode disposed on the window layer;
• the absorber layer is formed by a solution method;
• and
• the absorber layer is composed of CuInxGa(1-x)SySe(2-y) (where x is a real number of 0 to 1 and y is a real number of 0 to 2),
• the method comprising varying the ratio of In/Ga in the absorber layer to control the transmittance.