Method of manufacturing high-density CIS thin film for solar cell

This innovative technology relates to a method of manufacturing high-density CIS thin film for solar cell and a method of manufacturing a thin film solar cell using the CIS thin film. Specifically, this technology relates to a method of manufacturing CIS thin-film by coating CIS, CIGS or CZTS nano-powders on a substrate via non-vacuum coating, followed by heat treatment with the cavities between the nano-powders being filled with elements such as copper, indium, gallium, zinc, tin, etc.

Solar cells directly converting sunlight into electric energy have various merits such as avoidance of contamination, infinite resource and semi-permanent lifespan, and are thus anticipated as an energy source capable of solving the problem of energy depletion.

A key component in solar cell production is the use of a semiconductor material for solar energy absorption. A CIS or GCIS thin film is a compound semiconductor which possesses a higher conversion efficiency, of about 19.9%, than other thin film solar cells and, due to its capability to be fabricated to a thickness of 10 micros or less, can be stably operated even after long-term use. What’s more, CIS or GCIS is anticipated as an inexpensive, highly efficient solar cell capable of replacing silicon. Solar cells are classified into five types depending on materials for a photo-absorption layer, and a silicon solar cell is most widely used in the art. Recently, however, a rapid increase in raw material costs due to undersupply of silicon has led to increasing interest in thin film solar cells. Thin film solar cells are manufactured to a low thickness, thereby providing merits such as low consumption of material, lightweight, wide application ranges, and the like.

A GCIS solar cell is formed using a thin film having a thickness of several micrometres by vacuum deposition, or by precursor deposition in a non-vacuum state and heat treatment of the precursor-deposited thin film. Vacuum deposition is advantageous in that it provides a highly efficient absorption layer. However, vacuum deposition disadvantageously provides low uniformity and requires expensive equipment in forming a large area absorption layer, and causes a material loss of about 20% to 50%, which leads to high manufacturing costs.

The inventors of the present invention carried out extensive studies to obtain a method of manufacturing a high-density CIS thin film, CIGS thin film or CZTS thin film through the non-vacuum coating. Subsequently identifying that high-density CIS thin film can be formed when heat treating the CIS thin film, CIGS thin film, CZTS thin film, with cavities of the film filled with filling elements such as copper, indium, gallium, zinc, tin, and the like.

The technology, developed and presented by the KIER, has been conceived to solve the problems related to CIS fabrication for solar cells. This advanced technology offers a refined method for manufacturing high-density CIS thin film for solar cell and method of manufacturing thin film solar cell using the same, through a streamlined method which provides high-density CIS thin film while also minimising manufacturing costs and time requirements.

Method of manufacturing high-density CIS thin film for solar cell:

This advanced technology has two aspects, each geared to produce slightly different results depending on the requirement and capabilities of users:

• In accordance with one aspect of the invention, a method of manufacturing a high-density CIS thin film includes: preparing CIS nanoparticles, the process is broken down into 5 steps: (Step 1); dispersing the CIS nanoparticles and dissolving a binder in a solvent to prepare a CIS slurry (Step 2); dissolving a filling element-containing salt and a binder in a solvent to prepare a filling element-containing slurry (Step 3); mixing the CIS slurry and the filling element-containing slurry to prepare a slurry mixture (Step 4); and coating the slurry mixture onto a substrate to form a CIS thin film, followed by heat treatment (Step 5).
• In accordance with another aspect of the present invention, a method of manufacturing a high-density CIS thin film include: preparing CIS nanoparticles, the process is broken down into 5 steps: (Step A); dispersing the CIS nanoparticles and dissolving a binder in a solvent to prepare a CIS slurry (Step B); coating the CIS slurry onto a substrate to form a CIS thin film (Step C); dissolving a filling element-containing salt and a binder in a solvent to prepare a filling element-containing slurry (Step D); and coating the filling element-containing slurry onto the CIS thin film, followed by heat treatment (Step E).

A further aspect of the present invention provides a high-density CIS thin film, which includes a CIS thin film; and filling elements placed in cavities within the CIS thin film. Here, the filling elements are at least two elements selected from the group consisting of copper, indium, gallium, zinc, and tin. The CIS thin film may be a CIS thin film, a CIGS thin film, or a CZTS thin film.

The present invention was conceived to solve the problems of the related art, and one aspect of the present invention is to provide a high-density CIS thin film, which can reduce manufacturing costs using non-vacuum coating, and a method of manufacturing the same. The process outlined above details how the problem is met and overcome using this advanced CIS thin-film manufacturing technology. According to the exemplary embodiments, the CIS thin film is subjected to heat treatment with cavities of the CIS thin film filled with filling elements such as copper, indium, gallium, zinc, tin, and so on, thereby forming a high-density CIS thin film. When the high-density CIS thin film is applied to a photo-absorption layer of a thin film solar cell, the manufactured thin-film solar cell exhibits high efficiency.

Intellectual property status

Granted Patent

Patent number : 8569102

Where : USA

Current development status

Commercially available technologies

Desired business relationship

Technology selling

Patent licensing

Joint ventures

Technology development

New technology applications

Adaptation of technology to other markets