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For organnoboron compounds, the substituents on boron atoms are very important because they not only impact on the molecular stability but also significantly modulate the electronic structures and properties. In this manuscript, we synthesized two new B⟵N-containing azaacenes with propynyl groups on boron atoms through one-step Grignard reaction. Replacing fluorine atoms by propynyl groups greatly impacts on the electronic energy levels, especially enhancing the HOMO levels, thus leading to the narrowed HOMO-LUMO bandgaps. These B⟵N-containing azaacenes exhibit the NIR light-absorption (λabs = 706 nm for 2a and 762 nm for 2b) and fluorescence properties (λem = 740 nm for 2a and 802 nm for 2b), as well as multiple reversible redox behaviors, which are significantly different from the analogs with fluorine atoms. This study thus provides a functional substituent of boron atom, which may lead to new organoboron materials with fascinating properties.

Open-circuit voltage (VOC) of polymer solar cells (PSCs) is always in the range of 0.6–0.9 V and rarely exceeds 1.0 V. The common strategy to enhance VOC of PSCs is to use polymer donors with low-lying highest occupied molecular orbital energy level (EHOMO). In this manuscript, we report high VOC of 1.3 V for PSCs by further using a polymer acceptor with high-lying lowest unoccupied molecular orbital energy level (ELUMO). With poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole] (PCDTBT) as the donor and poly[(N,N′-bis(2-hexyldecyl)-diamine-bis(difluoro-borane)−2,2′-bipyridine)-alt-(2,5-thiophene)] (P-BNBP-T) as the acceptor, the PSC devices show the VOC of 1.30 V and power conversion efficiency (PCE) of 3.20%. This VOC is higher than that of the conventional acceptor materials by 0.4 V owing to the high-lying ELUMO of P-BNBP-T. We have also investigated the effect of processing solvents on the blend morphology and the device performance. Compared with high boiling-point solvent o-dichlorobenzene, low boiling-point solvent chloroform gives finer phase separation size, improved exciton dissociation and consequently better photovoltaic device performance. The demonstration of high VOC in this work indicates that there is large room for PCE enhancement of PSCs.