Research Highlights

Prof. Kilwon Cho Develops New Device Architecture for Enhancing the Power Conversion Efficiency of Organic Solar Cells

2015-10-19 407
 
Prof. Kilwon Cho
 
Prof. Kilwon Cho and Dr. Sae Byeok Jo of the Department of Chemical Engineering have developed a new universally applicable device architecture for enhancing the power conversion efficiency of organic solar cells. The research outcome was featured as a cover article in the highly respected international research journal Advanced Energy Materials.
 
Organic solar cells have gained much attention due to their feasibility in the realization of wearable and environmentally-friendly energy devices at a low production cost using flexible processing technologies. In organic solar cells, the sunlight is converted to electrical charges using organic semiconductors as a light absorbing materials. However, the chemical versatility of used organic semiconductors and the complexity of the multiple component system comprising them have only allowed case-by-case empirical approaches to the optimization of the organic solar cell devices, which seriously hindered the further enhancement of the performance of organic solar cells.
 
According to Prof. Cho’s research, the optoelectrical properties of organic solar cells could be systematically and meticulously tuned regardless of used organic semiconductors, by inducing “forced dipole alignment” at the interface of photoactive layers and electrodes. The research team introduced an additional layer comprising a blend of “ferroelectric” polymer and semiconductor nanocrystals underneath the light absorbing layer and applied a weak electrical bias for a brief moment. Since the ferroelectric materials could intrinsically retain induced dipole moments even after the electrical bias, the gradual and controllable alignment of dipole moment could be realized depending on the strength of the applied electrical bias. Those additional layer worked as a controllable “valve” for the electrons and holes generated in the light absorbing layer so that the electrical current generated by light absorption could be collected without any leakage and loss. The research team applied this approach to various organic solar cells and successfully demonstrated 80% increment in the lifetime of generated electrons and holes and, consequently, 10 to 400% increment in the performance of organic solar cells regardless of used organic semiconductors.
 
Prof. Cho emphasized, “This research will bring forward the further understanding of the device operation mechanism and the realization of high performance next-generation organic solar cells”.
 
This research was supported by the Global Frontier Research Center for Advanced Soft Electronics under the Ministry of Science, ICT & Future Planning.