am9b23366_si_001.pdf (1.36 MB)
The Role of the Hydrogen Bond between Piperazine and Fullerene Molecules in Stabilizing Polymer:Fullerene Solar Cell Performance
journal contribution
posted on 2020-03-18, 18:45 authored by Zerui Li, Jiankai Shan, Lingpeng Yan, Huimin Gu, Yi Lin, Hongwei Tan, Chang-Qi MaPiperazine
has been recently reported as a stabilizer for polymer:fullerene
solar cells that can minimize the “burn-in” degradation
of the cell. In this paper, the influence of N-substituents on the
stabilization effect of piperazine in P3HT:PC61BM cells
was investigated. Results confirmed that only piperazine derivatives
(PZs) with N–H bonds showed the stabilization effect, whereas
the bis-alkyl-substituted piperazine compounds cannot improve the
stability. An efficient photon-induced electron transfer (PET) process
between PZ and PC61BM was only detected for the N–H-containing
PZ:PC61BM blends, corresponding very well to the stabilization
effect of the PZs, which indicates that the PET process between PZ
and PC61BM stabilizes the cell performance, and the N–H
bond plays a critical role ensuring the PET process and the consequent
stabilization effect. Both 1H-NMR spectroscopy and theoretical
calculations confirmed the formation of N–H···O–C
and N–H···π bonds for the PC61BM:piperazine adduct, which was considered as the driving force that
promotes the PET process between these two components. In addition,
comparison of the calculated electron affinity energy (EA) and excitation energy (EEx) of PC61BM with/without piperazine confirmed that piperazine
doping is able to promote the electron transfer (which leads to the
formation of PC61BM anions) than the energy transfer (leads
to the formation of PC61BM excitons) between P3HT and PC61BM, which is beneficial for the performance and stability
improvement.