Optically tunable spin-exchange energy at donor:acceptor interfaces in organic solar cells
Abstract
Spin-exchange energy is a critical parameter in controlling spin-dependent optic, electronic, and magnetic properties in organic materials. This article reports optically tunable spin-exchange energy by studying the line-shape characteristics in magnetic field effect of photocurrent developed from intermolecular charge-transfer states based on donor:acceptor (P3HT:PCBM) system. Specifically, we divide magnetic field effect of photocurrent into hyperfine (at low field < 10 mT) and spin-exchange (at high field > 10 mT) regimes. We observe that increasing photoexcitation intensity can lead to a significant line-shape narrowing in magnetic field effect of photocurrent occurring at the spin-exchange regime. We analyze that the line-shape characteristics is essentially determined by the changing rate of magnetic field-dependent singlet/triplet ratio when a magnetic field perturbs the singlet-triplet transition through spin mixing. Based on our analysis, the line-shape narrowing results indicate that the spin-exchange energy at D:A interfaces can be optically changed by changing photoexcitation intensity through the interactions between intermolecular charge-transfer states. Therefore, our experimental results demonstrate an optical approach to change the spin-exchange energy through the interactions between intermolecular charge-transfer states at donor:acceptor interface in organic materials.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jul 14, 2014
- Source ID
- 10.1063/1.4889807
Entities
People
- Bin Hu
- Hengxing Xu
- Hongfeng Wang
- Huidong Zang
- Lei He
- Mingxing Li
Organizations
- Air Force Office of Scientific Research
- University of Tennessee