posted on 2021-10-21, 15:35authored byYi Zhang, Yan Wang, Tong Shan, Qingyun Wei, Yun Xiang Xu, Hongliang Zhong
Non-fullerene
acceptors (NFAs) with near-infrared (NIR) absorption
show promising advantages in organic solar cells (OSCs). However,
only a few NFAs can extend the absorption spectra over 1000 nm, and
their photovoltaic performance has been unsatisfactory so far. To
address this issue, three new NFAs, namely, 6-IFIC, 6-IF2F, and 6-IF4F,
were synthesized by simultaneously introducing π-bridge units
and different end groups. The π-bridge unit enlarges the conjugation
and planarizes the molecular geometry, leading to intense absorption
in the NIR range. The asymmetric configuration provides a large dipole
moment, enhances the intermolecular interaction, and tunes the miscibility,
consequently being beneficial for achieving a favorable morphology
in OSCs. When blended with a donor polymer PTB7-Th, the 6-IF2F-based
OSC yields the best power conversion efficiency (PCE) of 11.20%, which
is among the highest PCEs based on NFAs with absorption over 1000
nm. More importantly, the absorption of the blend film provides a
transparency window in the visible range from 400 and 650 nm. Therefore,
the semitransparent OSCs based on these three NFAs can achieve over
28% average visible transmittance.