GIST Professor Jae-Hyung Jang's research team develops broadband CIGS thin-film solar cell technology based on down-shifting quantum dots
□ Professor Jae-Hyung Jang of the School of Electrical Engineering and Computer Science at the Gwangju Institute of Science and Technology (GIST, President Seung Hyeon Moon) and Professor Ju-Hyung Yun of Incheon National University have succeeded in developing broadband CIGS thin-film solar cell technology using quantum dots.
* CIGS Thin Film Solar Cell: A thin-film solar cell that uses a compound semiconductor composed of copper (Cu), indium (In), gallium (Ga), and selenium (Se) as a solar absorbing layer.
∘ Quantum dots are nanosized semiconductor particles that can control their optical properties by controlling the constituent materials and size. Recently, it has been widely applied as an optical material for displays and photoelectric elements by utilizing the properties of the quantum dots.
∘ CIGS thin-film solar cells suitable for developing low-cost and high efficiency solar cells that can be applied not only to solar power plants but also to portable lightweight solar cells because of their high energy conversion efficiency.
□ Conventional CIGS thin-film solar cells absorb solar light of short wavelength band (300 ~ 520 nm) including ultraviolet region from transparent electrode * and buffer layer * on top of solar cells and convert solar energy of this wavelength band into electric energy. There is a limit in converting solar energy of this wavelength band into electric energy.
* Transparent Electrode: An electrode with high light transmittance and excellent electrical conductivity, formed on the surface of the solar cell on which light is incident. In CIGS thin-film solar cells, zinc oxide (ZnO) and aluminum-doped ZnO are mainly used.
* Buffer layer: CIGS light absorbing layer with p-type conductivity and n-type semiconductor for p-n junction. CdS thin-film solar cell mainly uses cadmium sulfide (CdS).
□ The researchers succeeded in developing quantum dots that emit light in the visible range by absorbing most of the light in the short wavelength band and applied it between the antireflective layer * of the CIGS solar cell and the transparent electrode layer. As a result, a broadband CIGS thin-film solar cell capable of converting not only visible light and infrared light but also ultraviolet sunlight into electric energy has been realized.
* Antireflection film: A film formed on the surface of a solar cell to reduce reflection loss of light. CIGS thin film solar cells mainly use magnesium fluoride (MgF2).
∘ In addition to solving the short wavelength band loss occurring on top of the existing CIGS thin-film solar cell, the combination of the quantum dots and the antireflective film minimized the luminescence loss and surface reflection loss of the quantum dots and realized high efficiency for the broadband CIGS thin-film solar cells.
