n-Octyl substituted quinoxaline-based polymer donor enabling all-polymer solar cell with efficiency over 17%

Recently, the power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs) have increased rapidly. To further increase the PCE of all-PSCs, it is necessary to create new donor polymers matching the polymer acceptors. In this paper, we synthesize a new quinoxaline-based polymer donor PBQ8 with n-octyl side chain on the quinoxaline unit, which possesses the same skeleton structure to the previously reported PBQ5 (with isooctyl side chain). The effects of alkyl side chains on the physicochemical properties of the polymer donor were investigated. In comparison with PBQ5, PBQ8 exhibits stronger intermolecular interactions and better molecular packing. When blending with polymer acceptor PY-IT, the PBQ8:PY-IT based devices demonstrated a higher PCE value of 17.04%, which is one of the highest PCEs occurred in the all-PSCs. And the PBQ5:PY-IT (PCE 15.56%, Voc 0.907 V, FF 69.72%, and J(sc) 24.60 mA cm(-2)) is much lower. The PBQ8:PY-IT blend displayed more efficient exciton dissociation, better molecular stacking properties, preferable phase separation and higher mobility. These indicate that as an effective method, side chain engineering can improve the efficiency of the all-PSCs. (c) 2022 Science China Press. Published by Elsevier B.V. and Science China Press. All rights reserved.

Automated summary

The power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs) have been increasing rapidly. This paper focuses on the synthesis of a quinoxaline-based polymer donor PBQ8 with a n-octyl side chain and investigates the effects of alkyl side chains on the physicochemical properties of the polymer donor. When blended with polymer acceptor PY-IT, PBQ8 exhibits stronger intermolecular interactions, better molecular packing, and achieves a higher PCE value of 17.04%. The study suggests that side chain engineering is an effective method to improve the efficiency of all-PSCs.