Polymer Acceptors with Flexible Spacers Afford Efficient and Mechanically Robust All-Polymer Solar Cells

High efficiency and mechanical robustness are both crucial for the practical applications of all-polymer solar cells (all-PSCs) in stretchable and wearable electronics. In this regard, a series of new polymer acceptors (P(A)s) is reported by incorporating a flexible conjugation-break spacer (FCBS) to achieve highly efficient and mechanically robust all-PSCs. Incorporation of FCBS affords the effective modulation of the crystallinity and pre-aggregation of the P(A)s, and achieves the optimal blend morphology with polymer donor (P-D), increasing both the photovoltaic and mechanical properties of all-PSCs. In particular, an all-PSC based on PYTS-0.3 P-A incorporated with 30% FCBS and PBDB-T P-D demonstrates a high power conversion efficiency (PCE) of 14.68% and excellent mechanical stretchability with a crack onset strain (COS) of 21.64% and toughness of 3.86 MJ m(-3), which is significantly superior to those of devices with the P-A without the FCBS (PYTS-0.0, PCE = 13.01%, and toughness = 2.70 MJ m(-3)). To date, this COS is the highest value reported for PSCs with PCEs of over 8% without any insulating additives. These results reveal that the introduction of FCBS into the conjugated backbone is a highly feasible strategy to simultaneously improve the PCE and stretchability of PSCs.

Automated summary

The introduction of a flexible conjugation-break spacer (FCBS) into polymer acceptors (P(A)s) enables the achievement of highly efficient and mechanically robust all-polymer solar cells (all-PSCs), improving both photovoltaic performance and mechanical stretchability.