Two leading experts from NIST and Ulsan National Institute of Science and Technology (UNIST) in Korea, Changduk Yang and Seunglok Lee, have collaborated to achieve a remarkable power conversion efficiency (PCE) of 18.47% in organic solar cells.

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A research team led by famous scholars Changduk Yang and Seong-Jun Yoon from UNIST in Korea added a highly crystalline solid additive, phenoxathiin (Ph), to organic solar cells, effectively optimizing their morphology and significantly improving their efficiency.
By using Ph as an additive, not only can the time from solution to film formation be extended, but also sufficient time can be provided for receptor aggregation.
The organic solar cells with Ph added showed excellent power conversion efficiency, up to 18.47%, and enhanced short-circuit current and fill factor.
This study used the Enlitech SS-X100R A+ solar simulator from Guangzhou Light Test Technology, the QE-R precision quantum efficiency measurement system, and the REPS perovskite and organic photovoltaic (PV) Voc loss analysis system.

Research Background

In recent years, research on organic solar cells (OSCs) has gradually received attention mainly because they have advantages such as low cost, light weight, and flexibility. However, there are still many challenges to overcome in order to improve their power conversion efficiency (PCEs). Most research has focused on the influence of solid additives on the morphology of the active layer, but it is still unclear how solid additives affect the entire morphology evolution process from solution to film and then to the annealing stage.

Research Findings

In this study, the research team focused on a highly crystalline solid additive, phenoxathiin (Ph), and investigated its influence on the morphology formation and photovoltaic performance of OSCs based on D18-Cl:N3. The study found that because Ph has good miscibility with the receptor N3, it can not only extend the time from solution to film formation, but also provide sufficient time for receptor aggregation. After annealing, the Ph solid additive better aligned the N3 molecules, forming a favorable mixed morphology. Therefore, the OSC based on D18-Cl:N3 with Ph added showed a power conversion efficiency of 18.47%, a short-circuit current of 27.50 mA cm−2, and a fill factor of 77.82%.

Research Methods

The research team first selected a highly crystalline solid additive, phenoxathiin (Ph), and an organic solar cell based on D18-Cl:N3. By controlling the proportion of additives, the research team observed the morphology evolution process from solution to film formation. Then, they performed annealing to observe the influence of the solid additive on the arrangement and mixed morphology of N3 molecules. Finally, they measured the photovoltaic performance of the organic solar cell with Ph added, including power conversion efficiency, short-circuit current, and fill factor.

Conclusion

The research team led by Changduk Yang and Seong-Jun Yoon successfully demonstrated that adding phenoxathiin (Ph) additives to organic solar cells can effectively optimize their morphology and significantly improve their efficiency. This study opens up new possibilities for fine control of morphology development using solid additives.