The
bulk photovoltaic effect (BPVE) has drawn intensive attention
due to its unique features that cannot be accessed with the conventional
photovoltaic effect. However, the BPVE is observed in noncentrosymmetric
materials and has been studied mainly for inorganic materials. Here,
we report a simple subphthalocyanine (SubPc) derivative that assembles
into a noncentrosymmetric columnar liquid crystal with the help of
a DC E-field. These columnar assemblies exhibit the BPVE over a wide
range of wavelengths up to 650 nm. Furthermore, just by sandwiching
this columnar assembly between two ITO electrodes, the resultant device
reaches a light-on/off ratio, I
light/I
dark, as high as 6.6 × 103,
indicating that the polar columnar assemblies with SubPcs are promising
for photodetectors.
To meet the imminent requirement of fullerene‐free electron acceptors, a new ladder‐type heteroarene benzodi(thienopyran) (BDTP) is designed and synthesized by embedding pyran rings in [2,2‐(2,5‐dialkyloxy‐1,4‐phenylene)dithiophene] (PDT) for organic photovoltaic (OPV) applications. Originating from the strong p–π conjugation of the oxygen atom in the pyran rings, electron‐rich BDTP results in the BDTP‐cored molecular acceptor, NBDTP, with strong intramolecular charge transfer effect. With sp3 carbons in pyran rings, NBDTP have the flexibility of targeted modification to resolve the solubility as well as the morphological tuning by handy alkyl chain attachment. As a result, the fusion of pyran rings in BDTP means that the acceptor exhibits a narrow optical band gap of 1.58 eV and a high LUMO energy level of −3.79 eV. Meanwhile, blend morphology of NBDTP‐based OPVs shows fine tunability via thermal annealing. Owing to the beneficial optical absorption, suitable energy‐level alignment, favorable molecule packing, and proper morphology, the optimized NBDTP‐based OPVs achieve a power conversion efficiency of up to 10.1%, which exemplifies the potential of utilizing molecular acceptors featuring ladder‐type heteroarenes for high‐performance OPVs.
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