Probing film-depth-related light harvesting in polymer solar cells via plasma etching
Shuang Gao,
Laju Bu,
Zhong Zheng,
Xudong Wang,
Weichen Wang,
Ling Zhou,
Jianhui Hou,
Guanghao Lu
Affiliations
Shuang Gao
School of Science and State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China
Laju Bu
School of Science and State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China
Zhong Zheng
State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Xudong Wang
Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
Weichen Wang
Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
Ling Zhou
Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710054, China
Jianhui Hou
State Key Laboratory of Polymer Physics and Chemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
Guanghao Lu
School of Science and State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China
Light harvesting is the first step of photovoltaic process in polymer solar cells. However, such donor: acceptor bulk junction layers are usually featured with vertical phase segregation as well as film-depth-dependent molecular aggregation, chain orientation and crystallinity, leading to a significant variation of photon absorption and exciton generation at different film-depths. We propose an experimentally and numerically accessible method to investigate the depth-dependent light harvesting behaviors in the active layer in polymer solar cells. A low-pressure oxygen plasma is utilized to etch the active layer gradually which is monitored by a light absorption spectrometer. Including the obtained sublayer absorption spectra into transfer matrix optical model yields depth-dependent optical properties and exciton generation profiles, which contribute to quantum efficiency and short-circuit current. This approach is helpful to optimize vertical material variation and provide insights into photovoltaic process.
