The heterointerface between organic and inorganic semiconductors widely presents in organic optoelectronics, especially for polymer solar cells (PSCs). [1][2][3] Ideally, to facilitate the charge extraction (or injection) at such heterojunction, it requires the presence of not only the minimized interfacial energy barriers between these two composition-different semiconductors, but also the enlargement of build-in field across the interfaces. [4,5] Within a few years, recently, the fast evolution of organic active components, particularly from fullerene to nonfullerene acceptors, has enabled rapid progresses of power conversion efficiencies (PCEs) for PSCs. [6][7][8][9][10][11][12][13][14][15][16][17] Notably, a number of optimal active layers can already achieve near 100% internal quantum efficiencies (IQEs) for the conversion of absorbed photons into photogenerated carriers. [6,18] Therefore, in such devices, the heterointerface governing charge extraction (or injection) becomes deterministic factors to affect the overall performance as well as stability of PSCs.For examples, among the high-performance PSCs, inverted ones have routinely employed metal oxides, such as ZnO and titanium oxide (TiO 2 ) as electron-transport layers (ETLs), [19,20] which have been paired with a large range of organic-active components with variable energetics and surface energies. One therefore can easily identify those conventional metal oxide ETLs; once employed for fullerene, PSCs should present significant mismatch to nowadays nonfullerene acceptors. [21][22][23][24] The mismatched energy levels between metal oxide and organic photoactive layers can create contact resistances to hinder charge extraction. [25] Besides, chemical and physic defects of metal oxides, such as dangling hydroxide (OH) or Zn vacancy on the surface or crystal boundary of ZnO, could trap charges to cause carrier recombination loss. [26] Moreover, the photocatalytic activities of semiconducting metal oxides should also pose significant impacts toward the contacted organic semiconductors. It has been known that ZnO and TiO 2 could generate reactive species upon excitation, such as hydroxide radical and superoxide radical anion in ambient, to degrade vulnerable organic semiconductors with active hydrogen and double bonds. [27] These interfacial issues not only hinder charge events at the heterointerface, Charge events across organic-metal oxide heterointerfaces routinely occur in organic electronics, yet strongly influence their overall performance and stability. They become even more complicated and challenging for the heterojunction conditions in polymer solar cells (PSCs), especially when nonfullerene acceptors with varied energetics are employed. In this work, an effective interfacial strategy that utilizes novel small molecule self-assembled monolayers (SAMs) is developed to improve the electronic and electric, as well as chemical properties of organic-zinc oxide (ZnO) interfaces for nonfullerene PSCs. It is revealed that the tailored SAMs with well-cont...
Ultralong organic phosphorescence (UOP) has aroused enormous interest in recent years. UOP materials are mainly limited to crystals or rigid host–guest systems. Their poor processability and mechanical properties critically hamper practical applications. Here, we reported a series of ultralong phosphorescent foams with high mechanical strength. Phosphorescence lifetime of the foam can reach up to 485.8 ms at room temperature. Impressively, lightweight gelatin foam can bear a compressive pressure of 4.44 MPa. Moreover, phosphorescence emission of polymer foam can be tuned from blue to orange through varying the excitation wavelength. Experimental data and theoretical calculations revealed that ultralong phosphorescence was ascribed to the fixation of multiple hydrogen bonds to the clusters of carbonyl groups. These results will allow for expanding the scope of luminescent foams, providing an ideal platform for developing ultralong phosphorescent materials with high mechanical strength.
Mechanical nonreciprocity, or the asymmetric transmission of mechanical quantities between two points in space, is crucial for developing systems that can guide, damp, and control mechanical energy. We report a uniform composite hydrogel that displays substantial mechanical nonreciprocity, owing to direction-dependent buckling of embedded nanofillers. This material exhibits an elastic modulus more than 60 times higher when sheared in one direction compared with the opposite direction. Consequently, it can transform symmetric vibrations into asymmetric ones that are applicable for mass transport and energy harvest. Furthermore, it exhibits an asymmetric deformation when subjected to local interactions, which can induce directional motion of various objects, including macroscopic objects and even small living creatures. This material could promote the development of nonreciprocal systems for practical applications such as energy conversion and biological manipulation.
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