UW Research Group Advances Microscopic Understanding of Electric Field Treatment

A University of Wyoming researcher’s group is revealing microscopic clues of the electric field treatment on organic solar cells.

TeYu Chien, a UW associate professor in the Department of Physics and Astronomy, and his research team have been expanding their expertise from inorganic, hard materials toward organic, soft materials, and they have exposed the microscopic understandings of the electric field treatment on organic solar cell materials. The group recently had its paper, “Elongated Nanodomains and Molecular Intermixing Induced Doping in Organic Photovoltaic Active Layers with Electric Field Treatment,” accepted by the ACS Applied Polymer Materials journal.

The paper focuses on studying the effects of electric field treatment on organic solar cell materials. It has been reported the electric field treatment at elevated temperature may enhance the performance of organic solar cells. However, the microscopic understanding is lacking. The key reason is that there is no suitable experimental technique for this type of measurement.

Chien’s team decided to use cross-sectional scanning tunneling microscopy, a technique developed in the group originally for the study of oxide interfaces. The researchers have expanded this technique to soft materials, organic molecules and polymers. The measurements they collected showed the polymer molecular domains are elongated along the electric field direction, which will facilitate the charge collections, while the molecular intermixing affects the electronic properties of the molecular domains, leading to a lower efficient charge separation.

These two phenomena are having competing effects in organic solar cell performance. The understandings may direct researchers in the field of polymers and organic molecules toward microscopic control of the molecules for various applications such as organic solar cells, organic light emission diodes and organic electrons.

Publication of the research indicates the group’s efforts have been recognized by experts in the polymer field, according to Chien. UW graduate student Rabindra Dulal was the lead author of the paper. He and fellow graduate student Aaron Wang prepared the samples and carried out the experiments and data analysis. Chien and his team also collaborated with researchers from Northwestern University and Lehigh University on the paper.