Fullerene-free polymer solar cells have been intensively investigated and the stateof-the-art single junction devices gave respected efficiencies beyond 16% in laboratory preparation scale with small device area of <0.05 cm 2 using small molecules as the acceptor materials. [1] The other main class of nonfullerene acceptor material is polymer acceptors and the organic solar cells made using polymeric donors and acceptors are called all-polymer solar cells (all-PSCs). Also for the laboratory device scale (<0.05 cm 2 ), the power conversion efficiencies (PCEs) of all-PSCs has grown from <2% in 2007 to 11%-12% in 2019. [2] In general, both small molecular acceptors and polymer acceptors possess advantages such as synthetic flexibility, strong and tunable absorption, and excellent solution processability. Compared to devices based on small molecule acceptors, all-PSCs manifest several other merits including (i) broad absorption bands with high extinction coefficients that can be tuned in the entire visible andIn the field of all-polymer solar cells (all-PSCs), all efficient polymer acceptors that exhibit efficiencies beyond 8% are based on either imide or dicyanoethylene. To boost the development of this promising solar cell type, creating novel electron-deficient units to build high-performance polymer acceptors is critical. A novel electron-deficient unit containing B←N bonds, namely, BNIDT, is synthesized. Systematic investigation of BNIDT reveals desirable properties including good coplanarity, favorable single-crystal structure, narrowed bandgap and downshifted energy levels, and extended absorption profiles. By copolymerizing BNIDT with thiophene and 3,4-difluorothiophene, two novel conjugated polymers named BN-T and BN-2fT are developed, respectively. It is shown that these polymers possess wide absorption spectra covering 350-800 nm, low-lying energy levels, and ambipolar film-transistor characteristics. Using PBDB-T as the donor and BN-2fT as the acceptor, all-PSCs afford an encouraging efficiency of 8.78%, which is the highest for all-PSCs excluding the devices based on imide and dicyanoethylene-type acceptors. Considering that the structure of BNIDT is totally different from these classical units, this work opens up a new class of electron-deficient unit for constructing efficient polymer acceptors that can realize efficiencies beyond 8% for the first time.
Polymer Solar CellsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.
The exploration of unipolar n-channel semiconductors plays an important role in the advance of organic complementary inverters and complementary logic circuits. Based on the conventional donor–acceptor type conjugated copolymers, the...
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