Volume 11 Issue 4
Fullerene-Based Photoactive Layers for Heterojunction Solar Cells: Structure, Absorption Spectra and Charge Transfer Process
Yuanzuo Li,Dawei Qi,Peng Song andFengcai Ma
1College of Science, Northeast Forestry University, Harbin 150040, Heilongjiang, China
2Department of Physics, Liaoning University, Shenyang 110036, Liaoning, China
*Authors to whom correspondence should be addressed.
Abstract
The electronic structure and optical absorption spectra of polymer APFO3, [70]PCBM/APFO3 and [60]PCBM/APFO3, were studied with density functional theory (DFT), and the vertical excitation energies were calculated within the framework of the time-dependent DFT (TD-DFT). Visualized charge difference density analysis can be used to label the charge density redistribution for individual fullerene and fullerene/polymer complexes. The results of current work indicate that there is a difference between [60]PCBM and [70]PCBM, and a new charge transfer process is observed. Meanwhile, for the fullerene/polymer complex, all calculations of the twenty excited states were analyzed to reveal all possible charge transfer processes in depth. We also estimated the electronic coupling matrix, reorganization and Gibbs free energy to further calculate the rates of the charge transfer and the recombination. Our results give a clear picture of the structure, absorption spectra, charge transfer (CT) process and its influencing factors, and provide a theoretical guideline for designing further photoactive layers of solar cells.
Keywords: heterojunction solar cells; fullerene derivatives; polymer (APFO3); absorption spectra; charge transfer