Manipulating Conjugated Polymer Backbone Dynamics through Controlled Thermal Cleavage of Alkyl Side Chains
Abstract
The morphological stability of an organic photovoltaic (OPV) device is greatly affected by the dynamics of donors and acceptors occurring near the device's operational temperature. These dynamics can be quantified by the glass transition temperature (Tg) of conjugated polymers (CPs). Because flexible side chains possess much faster dynamics, the cleavage of the alkyl side chains will reduce chain dynamics, leading to a higher Tg. In this work, the Tgs for CPs are systematically studied with controlled side chain cleavage. Isothermal annealing of polythiophenes featuring thermally cleavable side chains at 140 °C, is found to remove more than 95% of alkyl side chains in 24 h, and raise the backbone Tg from 23 to 75 °C. Coarse grain molecular dynamics simulations are used to understand the Tg dependence on side chain cleavage. X‐ray scattering indicates that the relative degree of crystallization remains constantduring isothermal annealing process. The effective conjugation length is not influenced by thermal cleavage; however, the density of chromophore is doubled after the complete removal of alkyl side chains. The combined effect of enhancing Tg and conserving crystalline structures during the thermal cleavage process can provide a pathway to improving the stability of optoelectronic properties in future OPV devices.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Aug 18, 2022
- Source ID
- 10.1002/marc.202200533
Entities
People
- Guorong Ma
- Haoyu Zhao
- Jordan J. Shanahan
- Luke Galuska
- Nathaniel Prine
- Stephanie Samson
- Wei You
- Wenjie Xia
- Xiaodan Gu
- Yunfei Wang
- Zhaofan Li
Organizations
- National Science Foundation
- North Dakota State University
- Office of Naval Research
- Office of Science
- University of North Carolina at Chapel Hill
- University of Southern Mississippi