The team from the Korea Institute of Science and Technology (KIST) has developed a high-efficiency, large-area organic solution processable solar cell – formed by coating a surface with a solar cell solution – by controlling the speed at which the solution of raw materials solidifies.
Solution-processable solar cells have been demonstrated in the laboratory over small areas, with the photoactive area which generates electricity having been very limited. In scaling these cells up to a large area to produce sufficient electric power to be commercially viable, researchers have found themselves facing issues of reduced performance and reproductivity due to material and process-related limitations.
The KIST team, led by Dr Hae Jung Son from the Photoelectric Hybrids Research Center, identified the difference in mechanism of film formation when scaling up in area. The process through which the solvent in the cell mixture evaporates to form a film occurs slowly, resulting in agglomeration and other issues which lower the efficiency of the solar cell. Speeding up this process would resolve this problem of scale.
Son and her colleagues managed to form these cells over larger areas through a spin-coating method typically used in laboratory research. This involves rapidly rotating the substrate during the film formation process, speeding up solvent evaporation and making it possible to form a film without the complications that occur during a lengthy evaporation process.
Based on this improved film formation technique, Son's team developed high-performance, large-area organic photovoltaics with a 30 per cent higher power-conversion efficiency than existing photovoltaics.
"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," said Son. "[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 commercialisation."
Son and her colleagues' resolution of this problem opens the door to the development of commercially viable novel photovoltaics.
For instance, a photovoltaic material could be created in the form of a paint applicable to any surface (e.g. the exterior of a vehicle or a building's roof), providing a low-cost and environmentally friendly source of power for people living in energy poverty and rendering it far easier to utilise space for photovoltaics. These photovoltaic panels could be maintained by simply re-applying the 'paint' whenever necessary.
