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Toward Efficient All-Polymer Solar Cells via Halogenation on Polymer Acceptors
Yuxiang Li1, Zhiyan Jia1,2, Qilin Zhang3
1School of Materials Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.
ACS Applied Materials & Interfaces
|June 26, 2020
Summary
Introducing halogenation, specifically fluorination and chlorination, in polymer acceptors significantly enhances electron mobility and film morphology. This leads to improved power conversion efficiency in all-polymer solar cells, demonstrating a key strategy for high-performance organic photovoltaics.
Area of Science:
- Materials Science
- Organic Electronics
- Photovoltaics
Background:
- Halogenation is a known method for tuning organic semiconductor properties.
- Systematic comparisons of non-halogenated and halogenated polymer acceptors in all-polymer solar cells (all-PSCs) are scarce.
- Developing efficient and stable organic solar cells requires optimized polymer acceptor design.
Purpose of the Study:
- To investigate the impact of different halogen species (non-halogenated, fluorinated, chlorinated) on the properties of IDIC-based polymer acceptors.
- To evaluate the performance of these polymer acceptors in all-polymer solar cells (all-PSCs).
- To provide insights into the structure-property relationships for designing high-performance polymer acceptors.
Main Methods:
- Synthesis of three IDIC-based narrow band gap polymer acceptors: PIDIC2T, PIDIC2T2F, and PIDIC2T2Cl, with varying donor units (bithiophene, fluorinated bithiophene, chlorinated bithiophene).
- Fabrication of all-PSCs using these polymer acceptors paired with either PBDB-T or PM6 polymer donors.
- Characterization of optoelectrical properties, including energy levels (LUMO, HOMO), optical band gap, electron mobility, thin-film morphology (rms roughness), and device performance (PCE, V_OC, J_SC, FF).
Main Results:
- PIDIC2T2Cl exhibited the highest power conversion efficiency (PCE) of 5.34% when paired with PBDB-T, attributed to favorable morphology and balanced charge carrier mobilities.
- Devices fabricated with PM6 donor showed further improvements: PM6:PIDIC2T (5.46%), PM6:PIDIC2T2F (4.96%), and PM6:PIDIC2T2Cl (7.11%).
- Chlorination in PIDIC2T2Cl led to enhanced electron mobility and optimized thin-film morphology, contributing to superior device performance.
Conclusions:
- Backbone halogenation, particularly chlorination, is an effective strategy to enhance electron mobility and thin-film morphology in polymer acceptors.
- The choice of halogen species significantly influences the performance of all-PSCs.
- This study provides valuable design guidelines for developing high-performance polymer acceptors through strategic halogenation for advanced organic photovoltaic applications.
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