image: The extended Su–Schrieffer–Heeger (SSH) tight-binding model was employed to accurately elucidate the electron transport behavior in donor polymer. The time evolutions of net charges on each site shown that after applying the relatively low electric field, the effective charge carrier transport can be achieved in the case of D unit coupling with PS. The charge center position calculation specifically revealed that the average transport velocity for D unit coupling with PS clearly superior to no coupling case. It is consistent with the phenomena observed in the experiment that D-A type donor coupling with PS is favorite for the electron transport.
Credit: ©Science China Press
The incorporation of polymeric insulators has led to notable achievements in the field of organic solar cells. Several research groups have demonstrated that polymeric insulators have significant effects in regulating molecular conformation, optimizing film crystallinity, and diluting defect states. However, current research suggests that the optimization of these physical properties is primarily attributed to the improvement of film morphology, which appears to be an inevitable result of the incorporation of insulating materials.
Recently, Professor Hang Yin’s research group at Shandong University proposed a general and completely new insulator blending effect in organic semiconductors: the insulator-donor electron wavefunction coupling effect, offering a novel strategy for enhancing the performance of organic solar cells. The research group observed that in a series of donor systems, the blending of insulators led to a significant enhancement in the electron mobility (up to 100 times). Interestingly, this attractive phenomenon only occurs when the D-A-type donor polymer was blended with an insulating material containing electron-rich side chain.
Theoretical calculation revealed that, in contrast to the traditional morphological regulation mechanism, the electron-rich group of the insulating material can couple with D unit of the donor polymer. This coupling effect effectively reducing the electron transport energy barrier and eventually facilitating intrachain electron transport within the polymer. The theoretical calculation results also consistent with the phenomena observed in the experiment by the research group.
Furthermore, the research group successfully utilized this coupling effect to fabricate PM6/L8-BO pseudo-bilayer organic solar cells, achieving a record power conversion efficiency (PCE) of 19.50% (certificated 19.18%). This work not only offers a novel perspective on the quantum effect of polymeric insulators in organic semiconductors, but also presents a simple yet effective method for enhancing the performance of organic solar cells.
The related research result was published in National Science Review under the title of “Insulator-Donor Electron Wavefunction Coupling in Pseudo-Bilayer Organic Solar Cells Achieving A Certified Efficiency of 19.18%”. The co-first authors of the article are Jiangkai Sun (PhD of Shandong University), Xue Yang (Master of Shandong University), and Ruijie Ma (postdoctoral researcher of the Hong Kong Polytechnic University). The corresponding authors of the article are Professors Hang Yin, Xiaotao Hao and Kun Gao from Shandong University, and Professor Gang Li from the Hong Kong Polytechnic University. Shandong University is the affiliation of the first author and the corresponding authors.
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See the article:
Insulator-donor electron wavefunction coupling in pseudo-bilayer organic solar cells achieving a certificated efficiency of 19.18%
https://doi.org/10.1093/nsr/nwae385
Journal
National Science Review