Method of fabricating copper indium gallium selenide (CIGS) thin film for solar cell.

This innovative technology relates to a method of fabricating a copper indium gallium selenide (CIGS) thin film for solar cells through co-vacuum evaporation, and a CIGS thin film for solar cells fabricated using the same method. This advanced method enables the fabrication of CIGS thin-film using a simplified process of co-vacuum evaporation. Using this method enables an elimination of commonly experienced deterioration in the properties of thin-film crystal growth while encouraging improved band-gap gradings and sustaining reduced production costs.

Solar cells are instrumental in climate change mitigation and adaption due to their capability for cheap mass production and minimal pollutant by-products. A key component in solar cell production is the use of a semiconductor material for solar energy absorption. CIGS, a semiconductor material, possess higher conversion than other thick film solar cell materials 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, CIGS is predicted to be a low-cost, high-efficiency solar material alternative to silicon.

Solar cells can be divided into numerous types depending on the materials used in their light-absorption layer. The most commonly available solar cells are silicon solar cells, unfortunately due to the high cost of pure silicon these cells are becomingly less economically viable for mass production. Thin film type solar cells are fabricated to a thin thickness and thus require less material consumption, as well as being lightweight and having an increase in application range.

A CIGS thin-film can be fabricated by vacuum deposition or non-vacuum coating. Particularly, vacuum deposition may include co-evaporation, in-line evaporation, a two-step process (precursor-reaction), and the like. Co-evaporation has traditionally been used to fabricate high-efficiency CIGS thin-film solar cells. However, co-evaporation technology is difficult to commercialisation due to the complicated nature of the process involved and the challenge of fabricating a large area solar cell. A partial solution to these issues has been the design of two-step (deposition/selenization) processes capable of facilitating mass production. However, these newly designed process often encounters drawbacks relating to scaling-up of technology and regulation of the flux of elements in each production step. Subsequently, there is a need for a simplified process of fabricating CIGS thin-film for solar cells which can achieve high crystal growth and improved band-gap grading.

The technology, developed and presented by the KIER, has been conceived to solve the problems related to CIGS fabrication. This advanced technology offers a refined method of fabricating copper indium gallium selenide (CIGS) thin film for solar cells, using a streamlined co-vacuum evaporation process capable of maintaining crystal growth and band gas grading while also minimising production time and cost, as compared with conventional co-vacuum evaporation processes.

Method of fabricating copper indium gallium selenide (CIGS) thin film for solar cell:

This streamlined method for fabricating copper indium gallium selenide (CIGS) thin film is achieved through the completion of several intricate steps. Firstly, Copper (Cu), Gallium (Ga) and Selenium (Se) are deposited on a substrate, with a temperature ranging from 500° C. to 600° C. using a process of co-vacuum evaporation (the co-vacuum evaporation may be performed for 2 minutes to 15 minutes). Next, Cu, Ga, Se and In (Indium) are deposited through co-vacuum evaporation while maintaining the same substrate temperature as in the previous step (the co-vacuum evaporation may be performed for 8 minutes to 30 minutes). The third step of this process is the depositing of Ga and Se through co-vacuum evaporation, followed by depositing Se alone through vacuum evaporation while lowering the temperature of the substrate, in this stage the vacuum evaporation of Se alone may be performed until the substrate temperature is lowered to 200° C. (co-vacuum evaporation of Ga and Se may be performed for 10 seconds to 180 seconds).

The method of fabricating a CIGS thin film for solar cells through co-vacuum evaporation according to the present invention can realise crystal growth and band-gap grading by Ga composition distribution while simplifying process steps and significantly reducing a film-deposition time, as compared with a conventional co-vacuum evaporation process, thereby providing an improvement in process efficiency.

This technology has numerous benefits, chiefly being the advancement of solar cell technology, a key component in the global renewable energy sector. The method detailed offers opportunities to reduce resource use, notably silicon use, and provide cost-effective chemical replacements. What’s more this simplified process enables the minimisation of production costs and film-deposition time.

Intellectual property status

Granted Patent

Patent number : 9472708

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