New Solution for Painted Solar Cells

Researchers in Korea have success­fully developed a high-efficiency large-area organic solution processable solar cell by controlling the speed at which the solution of raw materials for solar cells became solidified after being coated. The team led by Hae Jung Son from the Photo-electronic Hybrids Research Center of the Korea Institute of Science and Techno­logy (KIST) announced that they have identified the dif­ference in the mechanism of film formation between a small area and a large area of organic solar cells in a solution process and, by resolving the issue concerning the related process tech­nology, developed a high-efficiency large-area organic photo­voltaics.

Prototype of a high-efficiency solar cell on a large area through solution process method that utilizes spin coating. (Source: KIST)

If a photovoltaic material is made in the form of paint that can be applied to any surface, such as the exterior of a building or a car, it will be possible to achieve energy self-sufficiency and provide low-cost eco-friendly energy to those suffering from energy poverty. Not only that, it will be easy to utilize space for installation of photo­voltaics even on urban buildings, and ideally, the photo­voltaic panels will be maintained by re-applying the paint. When it comes to solution proces­sable solar cells, which work by coating the surface with the solar cell solution, the photo­active area that generates elec­tricity still remain on a laboratory scale. When applied to a large area to produce sufficient electric power for it to be practical, there are issues related reduced performance and repro­ducibility due to material- and process-related limitations, and this has been an obstacle to commerciali­zation.

Son’s team revealed that commer­cially available organic materials become easily crystal­lized, which makes them unsuitable for large-area solution processes. In the case of the large-area solution process for industrial uses, the process through which the solvent in which the solar cell material is dissolved evaporates to form a film occurs slowly, thereby resulting in agglo­meration and other phenomena, and this in turn lowers the efficiency of the solar cell. As for the spin coating method, which is a small-area process employed in labora­tory research, the substrated is rapidly rotated during the film for­mation process in order to speed up the solvent eva­poration, and this makes it possible to form a film without the afore­mentioned problem concerning reduced efficiency.

Based on this information, the researchers developed high-performance large-area organic photo­voltaics by controlling the solvent eva­poration rate following the coating step in a large-area solution process as a way to form a film optimized for solar cell performance. As a result, high-efficiency large-area organic photovoltaics with 30 % higher power conversion effi­ciency than existing photo­voltaics were attained. Son said, “The core design principles of solar cell materials capable of high-quality large-area using the solution will accelerate the develop­ment of solution processable solar cells in the future. [This study] has contri­buted to not only raising the effi­ciency of next-generation solution processable solar cells but also the development of core technology for manufacturing large-area solar cell materials required for commerciali­zation.” (Source: KIST)

Reference: S. H. Park et al.: Developement of highly efficient large area organic photovoltaic module: Effects of nonfullerene acceptor, Nano Energy 77, 105147 (2020); DOI: 10.1016/j.nanoen.2020.105147

Link: Photo-Electronic Hybrids Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea

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