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Charge trapping in mixed organic donor-acceptor semiconductor thin films
Shota Nunomura1, Xiaozhou Che, Stephen R Forrest
1Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan, 48109, USA; Research Center for Photovoltaic Technologies, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, 305-8568, Japan.
This study quantifies charge trap density in organic solar cells using a pump-probe method. Higher trap density correlates with reduced cell performance, highlighting trapping
Area of Science:
- Materials Science
- Organic Electronics
- Photovoltaics
Background:
- Organic solar cells (OSCs) efficiency is limited by charge carrier trapping.
- Understanding trap density is crucial for optimizing OSC performance.
- Small-molecule organic semiconductors and donor-acceptor blends are key OSC materials.
Purpose of the Study:
- To quantitatively determine trap density in organic semiconductor thin films and blends.
- To correlate trapped charge density with organic solar cell performance.
- To investigate the influence of nanocrystalline domains on charge trapping.
Main Methods:
- Application of a pump-probe technique to induce trapped charges optically.
- Measurement of photocurrent contributions from trapped charges.
- Quantitative analysis of trap density in organic semiconductor materials.
Main Results:
- Established a method for quantifying trap density in OSC materials.
- Demonstrated a direct correlation between trapped charge density and cell performance.
- Observed dependence of charge trapping on the presence of nanocrystalline domains.
Conclusions:
- The pump-probe method provides accurate trap density measurements for OSCs.
- Reducing charge trapping is essential for improving organic solar cell efficiency.
- Nanocrystalline domain engineering may mitigate charge trapping in OSCs.
