Issue 36, 2019

Self-doping n-type polymer as a cathode interface layer enables efficient organic solar cells by increasing built-in electric field and boosting interface contact

Abstract

Self-doped polymer cathode interface materials for organic solar cells have been widely investigated to enhance the ohmic contact between the electrode and the photoactive layer. Herein, a novel polymer named PBTA-FN with self-doping effect was successfully synthesized by incorporating benzotriazole (BTA) as an electron-deficient group and a fluorene containing an amino group. In favor of the n-type backbone and amine-based groups, an obvious n-type doping was obtained, resulting in the dramatically improved conductivity of PBTA-FN. Subsequently, PBTA-FN and PFN as cathode interface layers (CILs) were successfully applied in the organic solar cells based on PBDB-T-2F:IT-4F. A notable power conversion efficiency of 12.18% and 11.03% could be achieved with PBTA-FN and PFN as CILs, respectively. PBTA-FN showed better planarity than PFN as observed from the results obtained via density functional theory. The self-doping behaviour of PBTA-FN was determined by electron paramagnetic resonance, which exhibited a higher mobility and carrier density. The water contact angle results on the surface of the active-layer/PBTA-FN bilayer suggested that the PBTA-FN surface polarity was improved, which was attributed to the larger interface dipole. Thus, PBTA-FN can reduce the work function of an Al electrode and enhance the built-in electric potential, which were further confirmed by ultraviolet photoelectron spectroscopy and Mott Schottky curves, and the related device produced a higher Voc (0.88 V) than PFN (0.86 V). This work provides a deeper understanding of the PBTA-FN interlayer mechanism and has a potential application in optoelectronic devices.

Graphical abstract: Self-doping n-type polymer as a cathode interface layer enables efficient organic solar cells by increasing built-in electric field and boosting interface contact

Supplementary files

Article information

Article type
Paper
Submitted
29 jun 2019
Accepted
08 aug 2019
First published
12 aug 2019

J. Mater. Chem. C, 2019,7, 11152-11159

Self-doping n-type polymer as a cathode interface layer enables efficient organic solar cells by increasing built-in electric field and boosting interface contact

Y. Wang, Z. Liang, X. Li, J. Qin, M. Ren, C. Yang, X. Bao, Y. Xia and J. Li, J. Mater. Chem. C, 2019, 7, 11152 DOI: 10.1039/C9TC03506K

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