Stable and Efficient Organic Solar Cell

A joint research team has developed a new kind of organic solar cell, fabricated on a flexible substrate. (Source: UNIST)

A joint research team has developed a new kind of organic solar cell, fabricated on a flexible substrate. (Source: UNIST)

A new type of organic solar cells (OSC) with 11.6% efficiency has been developed by a research team, affiliated with Ulsan National Institut of Science and Techno­logy. This solar cell maintained almost 80% of its initial efficiency after 60 days long-term test under elevated temperatures up to 120 degrees. In the study, the research team, led by HyeSung Park and Chang Duck Yang of Energy and Chemical Engi­neering has developed an effective and simple strategy to simul­taneously improve and stablize the performance of OSCs by applying small amounts of the macro­molecular additive to the photo­active layer in OSCs. This is a unique and unpre­cedented method, which applies the macro­molecular additive to control the molecular weight.

The team reports that “The use of the macro­molecular additive introduced in this study has great potential for broad appli­cations with other OSC systems, which will accelerate the commer­cial viability of photo­voltaic techno­logy.” Organic solar cells are made of thin layers of organic materials with thickness in the 100 nanometer range. The light-absorbing material of OSCs absorbs sunlight to generate electric charge carriers. The efficiency of OSCs are often affected by the materials added to the photo­active layers.

In this work, the research team introduced the first demon­stration of the use of a well-known n-type conjugated polymer, as the macro­molecular additive into the photoactive layer of OSCs, and report a remarkable enhance­ment in the device performance yielding high efficiency with improved stability. Using the proposed method, they also demonstrated strong thermal stability in the additive-modified OSCs at elevated tempe­ratures, as well as long-term operation stability. In addition, by using the ITO-free archi­tecture on flexible PET substrates, the team success­fully demonstrated flexible solar cells processed with the macro­molecular additive.

Park states, “Due to its great applicability and easy accessibility, the use of the macro­molecular additive introduced in this study has great potential for broad appli­cations with other OSC systems, which will accelerate the commercial viability of photo­voltaic techno­logy.” This study also includes the analysis of the optimi­zation of power conversion efficiency in OSCs, the charge carrier transport pro­perties in OSCs, as well as the changes in the morpho­logy of the photo­active materials induced by the macro­molecular additive. The research team attributes the improved performance to advan­tageous changes in the morphology of the photo­active materials induced by the macro­molecular additive. Yang notes, “Our research is important in showing the influence of molecular weight on power conversion efficiency of OSCs.” (Source: UNIST)

Reference: K. H. Park et al.: The use of n-type macromolecular additive as a simple yet effective tool for improving and stabilizing the performance of organic solar cells, Energy Environ. Sci.,  online 12 September 2016; DOI: 10.1039/C6EE02255C

Link: Dept. of Energy Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology UNIST, Ulsan, Republic of Korea

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