NIR-absorbing polymer acceptor for efficient all-polymer solar cells with a record-high photocurrent of 26.5 ​mA ​cm−2

Abstract

Achieving high short-circuit current density (JSC) to boost power conversion efficiency (PCE) of all-polymer solar cells (all-PSCs) is a major challenge, mainly due to the difficulty in developing high-performance near-infrared (NIR)-absorbing polymer acceptors. Herein, a new polymer acceptor named PY2Se–4F employing a Y-series small-molecule acceptor as the precursor is designed and synthesized. Thanks to its unique molecular backbone structure combining selenophene-fused central core and bi-fluorinated end-group, PY2Se–4F shows desirable NIR-absorption with a spectral onset approaching 1000 ​nm, which is beneficial for obtaining high JSC when matched with wide bandgap polymer donors such as PM6 and D18. For the binary all-PSCs, PM6:PY2Se–4F delivers a record-high JSC of 26.5 ​mA ​cm−2, which is superior to that of D18:PY2Se–4F, mainly due to stronger absorption in the range of 600–700 ​nm. In contrast, the D18:PY2Se–4F combination exhibits more favorable blend morphology, higher and more balanced charge-transporting, and less non-radiative energy loss compared with the PM6:PY2Se–4F. As a result, the D18:PY2Se–4F-based devices offer an improved PCE of 16.1 ​% with a JSC of 25.5 ​mA ​cm−2 and both higher photovoltage and fill factor, while the related PCE and JSC are ones of the top values among the reported binary all-PSCs. The results indicate that PY2Se–4F is a promising NIR-absorbing polymer acceptor for obtaining efficient all-PSCs with record-high JSC.