Optical studies of native defects in π-conjugated donor–acceptor copolymers
Abstract
We used multiple spectroscopies such as photoinduced absorption (PIA), magneto photoinduced absorption, and doping induced absorption for studying native defects in π-conjugated donor–acceptor copolymer chains of benzodithio-phene fluorinated benzotriazole. The PIA spectrum contains characteristic photoinduced absorption bands that are due to polarons and triplet exciton species, whose strengths have different dependencies on the modulation frequency, temperature, and laser excitation, as well as magnetic field response. We found that the native defects in the copolymer chains serve as efficient traps that ionize the photoexcited excitons, thereby generating charge carriers whose characteristic optical properties are similar, but not equal to those of intrachain polarons formed by doping. The native defects density is of the order of 1017 cm−3 indicating that most of the copolymer chains contain native defects upon synthesis; however, this does not preclude their used-for photovoltaic applications.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jan 19, 2018
- Source ID
- 10.1063/1.5012995
Entities
People
- Dipak Khanal
- Evan Lafalce
- Sangita Baniya
- Wei You
- Zeev Valy Vardeny
Organizations
- Air Force Office of Scientific Research
- National Science Foundation
- University of North Carolina
- University of Utah