In their work, HI ERN scientists Dr. Olivier Ronsin and Prof. Jens Harting have analyzed the relationship between manufacturing processes and the resulting structures in greater detail. For the first time, the interaction of all relevant physical processes for the fabrication of organic solar cells was theoretically investigated in a coherent framework. The results of the simulations, which were recently published in the journal ACS Applied Materials & Interfaces, are in agreement with experimental results. This lays the foundation for determining physical design rules for ink formulation and processing conditions to optimize cell performance. The approach can be applied to newer organic material systems in the future.
The further development of organic solar cells has been a major research topic not only since the energy crisis. Organic solar cells consist of thin films and are considered potentially cheaper and more versatile than conventional solar cells. However, to date, they still have lower performance and shorter lifetimes than conventional solar cells. HI ERN researchers have now been able to perform realistic simulations of real organic solar cells for the first time. This new approach is an important step in the development of cheaper and more powerful organic solar cells. In the future, it can be applied to both newer organic material systems and perovskite solar cells to further optimize the performance of printed solar cells.
In organic solar cells, the photoactive layer consists of at least two materials. The performance is strongly dependent on the so-called bulk hetero-junction (BHJ) morphology in which the materials arrange themselves when the wet-deposited solution dries. However, the relationship between process and structure is still poorly understood, so scientific progress via "trial and error" has so far taken a long time.
In this work, a recently developed so-called coupled phase-field fluid mechanics framework is used to simulate the drying process. This makes it possible for the first time to study the interplay of all relevant physical processes such as evaporation, crystal nucleation and growth, and liquid demixing in a single coherent theoretical framework. The expected benefit of such an approach is to identify physical design rules for ink formulation and processing conditions to optimize cell performance. It could be applied to newer organic material systems in the future.
Video shows section of a simulated 150-nanometer-thick bulk hetero-junction morphology at the end of the fabrication process. This photoactive layer consists of a material mixture of polymers (red) and small molecules (green).
Olivier J. J. Ronsin, Jens Harting
Formation of Crystalline Bulk Heterojunctions in Organic Solar Cells: Insights from Phase-Field Simulations
ACS Appl. Mater. Interfaces 2022, 14, 44, 49785–49800
Publication Date: October 25, 2022
DOI: 10.1021/acsami.2c14319
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