A Tandem Polymer Solar Cell Based on Non-fullerene-acceptors Yields an Efficiency Approaching 15%

In polymer solar cells (PSCs), the blends of polymer donors and fullerene-based acceptors have been predominantly used for over two decades. This situation has been challenged owing to the rapid progress in non-fullerene (NF) PSCs. Up to now, the power conversion efficiencies (PCEs) of single-junction NF-PSCs have reached over 13% and surpassed that of the fullerene-based counterparts. Tandem double-junction solar cells are intrinsically more potential for enhancing PCE but bring more challenges for material design and device fabrication. Recently, in order to optimize light response spectrum of tandem NF-PSCs and hence to promote PCE, Hou et al. modulated the photoactive layer compositions by adopting a series of polymer donors and NF-acceptors. They found that light response spectrum of the blend of J52-2F:IT-M was well complementary with that of PTB7-Th:IEICO-4F, and as a result, the tandem NF-PSC based on these two blends could offer a broad and strong light response spectra covering 400 - 1000 nm. After optimizing device fabrication process, they realized a PCE of 14.9%, which is the top value in the field. Herein, by making a brief overview of NF-PSCs and highlighting this outstanding result, this short essay not only aims to attract attention to the rapid progress made by Chinese academic community but also delivers the expectation for the bright future of NF-PSCs.