Recently, solution‐processed organic solar cells combining small‐molecule donor and nonfullerene acceptor have achieved breakthrough results with the certified efficiency over 15%. These impressive ...progresses are driven by the concerted efforts of modifying the donor and acceptor materials and optimizing the morphology. Considering the defined chemical structures and easily tuned properties of small‐molecule materials, it is of great necessity and importance to pay more attentions on the topic of all‐small molecule organic solar cells. Here, we summarize the recent progress of all‐small molecule organic solar cells from the prospect of materials' evolutions and expect to provide some hints for its future developments. The involved small‐molecule donors including oligothiophene‐, benzodithiophene‐, naphthodithiophene‐, and porphyrin‐based materials are discussed to illustrate the relationship of chemical structures, properties, and device performance. Then, the small‐molecule nonfullerene acceptors in all‐small molecules organic solar cells are discussed to highlight their vital role. Finally, we will present the challenges and future of this research area.
Solution processed organic solar cells using small‐molecule electron donor and acceptor have demonstrated impressive efficiencies over 15% recently. The review presents the progress of all‐small molecule organic solar cells from the evolutions of small‐molecule donors and small‐molecule nonfullerene acceptor, respectively. The challenge and future development in the all‐small molecule organic solar cells have been discussed.
Although the multiple-component (MC) blend strategy has been frequently used as a very effective way to improve the performance of organic solar cells (OSCs), there is a strong need to understand the ...fundamental working mechanism and material selection rule for achieving optimal MC-OSCs. Here we present the 'dilution effect' as the mechanism for MC-OSCs, where two highly miscible components are molecularly intermixed. Contrary to the aggregation-induced non-radiative decay, the dilution effect enables higher luminescence quantum efficiencies and open-circuit voltages (V
) in MC-OSCs via suppressed electron-vibration coupling. The continuously broadened bandgap together with reduced electron-vibration coupling also explains the composition-dependent V
in ternary blends well. Moreover, we show that electrons can transfer between different acceptors, depending on the energy offset between them, which contributes to the largely unperturbed charge transport and high fill factors in MC-OSCs. The discovery of the dilution effect enables the demonstration of a high power conversion efficiency of 18.31% in an MC-OSC.
The recent development of quasi‐2D perovskite solar cells have drawn significant attention due to the improved stability of these materials and devices against moisture compared to their 3D ...counterparts. However, the optoelectronic properties of 2D perovskites need to be optimized in order to achieve high efficiency. In this work, the effect of spacer cations, i.e., phenethylammonium (PEA), 4‐fluorophenethylammonium (F‐PEA), and 4‐methoxyphenethylammonium (MeO‐PEA) on the optoelectronic properties and device performance of quasi‐2D perovskites is systematically studied. It is observed that both larger and more hydrophobic cations can improve perovskite stability against moisture, while larger size can adversely influence the device performance. Interestingly, with F‐PEA or MeO‐PEA, distribution of n value can be shifted toward high 3D content in quasi‐2D perovskite layers, which enables lower bandgaps and possibly lower exciton binding energy. Due to the best charge transport and lowest bandgap, the F‐PEAI‐based quasi‐2D perovskite (n = 5) solar cell shows a highest power conversion efficiency (PCE) of 14.5% with excellent stability in air with a humidity of 40–50%, keeping 90% of the original PCE after 40 d. It is believed that the approach may open a way for the design of new organic spacer cations for stable low‐dimensional hybrid perovskites with high performance.
The 4‐fluorophenethylammonium iodide based quasi‐2D perovskite (n = 5) solar cell shows a power conversion efficiency of 14.5% with excellent stability in air, with a humidity of 40–50%, maintaining 90% of the original efficiency after 40 d.
It has been a challenging topic and perpetual task to design and synthesize covalent macrocycles with characteristic self-assembling behaviors and excellent host-guest properties in supramolecular ...chemistry. Herein, we present a family of macrocyclic diphenylaminenarenes (DPAns, n = 3-7) consisting of methyldiphenylamine units through a facile one-pot synthesis strategy. Unlike many other reported macrocyclic arenes, the resultant non-planar DPAns feature intrinsic π-π stacking interactions, interesting self-assembling behaviors and ethene/ethyne capture properties. Specifically, strong multiple intermolecular edge-to-face aromatic interactions in DPA3 have been systematically investigated both in solid and solution states. The intriguing findings on the intermolecular edge-to-face stacking interaction mode in the macrocycle would further highlight the importance of noncovalent π-π interaction in supramolecular self-assembly. This study will also shed light on the macrocyclic and supramolecular chemistry and, we expect, will provide a direction for design and synthesis of covalent macrocycles in this area.
Sophisticated mechanically interlocked molecules (MIMs) with interesting structures, properties and applications have attracted great interest in the field of supramolecular chemistry. We herein ...report a highly efficient self-assembly of heterometallic triangular necklace 1 containing Cu and Pt metals with strong antibacterial activity. Single-crystal X-ray analysis shows that the finely arranged triangular necklace 1 has two racemic enantiomers in its solid state with intriguing packing motif. The superior antibacterial activity of necklace 1 against both standard and clinically drug-resistant pathogens implies that the presence of Cu(I) center and platinum(II) significantly enhance the bacterium-binding/damaging activity, which is mainly attributed to the highly positively charged nature, the possible synergistic effect of heterometals in the necklace, and the improved stability in culture media. This work clearly discloses the structure-property relationships that the existence of two different metal centers not only facilitates successful construction of heterometallic triangular necklace but also endows it with superior nuclease properties and antibacterial activities.
L
uminescent open-shell organic radicals have recently been regarded as one of the most potential materials in organic light-emitting diodes(OLEDs). Herein, we have synthesized two new organic ...radicals, namely tris{4-4-(
tert
-butyl)phenoxy-2,6-dichlorophenyl}methane radical(TTM-O) and tris(4-{4-(
tert
-butyl)-phenylthio}-2,6-dichlorophenyl)methane radical(TTM-S), by the substitution of chalcogen atom elements at the
para
position of conventional tris(2,4,6-trichlorophenyl)methyl(TTM) radical moiety. Interestingly, both TTM-O and TTM-S exhibited significantly enhanced photostability compared with the unsubstituted TTM radical parent. Moreover, the chalcogen atom also had a crucial impact on the photoluminescence quantum yield(PLQY) of the radicals,
i.e.
, the PLQY of TTM-S was greatly enhanced compared to TTM radical while TTM-O was nearly non-emissive. Particularly, TTM-S showed intense PLQY of 37.54% and 185-fold longer photostability than that in cyclohexane solution of TTM.
Photodetectors with ultrafast response are explored using inorganic/organic hybrid perovskites. High responsivity and fast optoelectronic response are achieved due to the exceptional semiconducting ...properties of perovskite materials. However, most of the perovskite‐based photodetectors exploited to date are centered on Pb‐based perovskites, which only afford spectral response across the visible spectrum. This study demonstrates a high‐performance near‐IR (NIR) photodetector using a stable low‐bandgap Sn‐containing perovskite, (CH3NH3)0.5(NH2CHNH2)0.5Pb0.5Sn0.5I3 (MA0.5FA0.5Pb0.5Sn0.5I3), which is processed with an antioxidant additive, ascorbic acid (AA). The addition of AA effectively strengthens the stability of Sn‐containing perovskite against oxygen, thereby significantly inhibiting the leakage current. Consequently, the derived photodetector shows high responsivity with a detectivity of over 1012 Jones ranging from 800 to 970 nm. Such low‐cost, solution processable NIR photodetectors with high performance show promising potential for future optoelectronic applications.
A high‐performance NIR photodetector derived from a stable low optical bandgap (E
g) Sn‐containing perovskite, MA0.5FA0.5Pb0.5Sn0.5I3, is introduced. Ascorbic acid is used as an effective antioxidant additive to enhance the performance of the photodiode. Finally, a high detectivity of over 1012 Jones between 800 and 970 nm with a high response rate is achieved.
To explore a new supramolecular interaction as the main driving force to induce hierarchical self-assembly (HSA) is of great importance in supramolecular chemistry. Herein, we present a ...radical-induced HSA process through the construction of well-defined rhomboidal metallacycles containing triphenylamine (TPA) moieties. The light-induced radical generation of the TPA-based metallacycle has been demonstrated, which was found to subsequently drive hierarchical self-assembly of metallacycles in both solution and solid states. The morphologies of nanovesicle structures and nanospheres resulting from hierarchical self-assembly have been well-illustrated by using TEM and high-angle annular dark-field STEM (HAADF-STEM) micrographs. The mechanism of HSA is supposed to be associated with the TPA radical interaction and metallacycle stacking interaction, which has been supported by the coarse-grained molecular dynamics simulations. This study provides important information to understand the fundamental TPA radical interaction, which thus injects new energy into the hierarchical self-assembly of supramolecular coordination complexes (SCCs). More interestingly, the stability of TPA radical cations was significantly increased in these metallacycles during the hierarchical self-assembly process, thereby opening a new way to develop stable organic radical cations in the future.
Open-shell singlet diradicaloids display unique electronic, nonlinear optical, and magnetic activity and could become novel molecular materials for organic electronics, photonics, and spintronics. ...However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this Article, we report our efforts toward a tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties, and chemical reactivity were systematically investigated by various experimental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device, and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introduction of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/antiaromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.
Triphenylamine (TPA) derivatives and their radical cation counterparts have successfully demonstrated a great potential for applications in a wide range of fields including organic redox catalysis, ...organic semiconductors, magnetic materials, etc., mainly because of their excellent redox activity. The stability of TPA radical cation has significant effect on the properties of the TPA-based functional materials, especially in relation to their electronic properties. Considering the instability of parent TPA radical cation, many efforts have been devoted to the development of stable TPA radical cations and related materials. Among them, TPA radical cation-based macrocycles have attracted particular attention because their large delocalized structures can stabilize the TPA radicals, thus endow them with outstanding redox behaviors, multiple resonance structures, and wide application in various optoelectronic devices. In this review, we give a brief introduction of organic radicals and the documented stable TPA radicals. Subsequently, a number of TPA radical cation-based macrocycles are comprehensively surveyed. It is expected that this minireview will not only summarize the recent development of TPA radical cations and their macrocycles, but also shed new light on the prospect of the design of more sophisticated radical cation-based architectures and related materials.
This review summarizes the design, preparation, characterization, and the potential application of triphenylamine radical cations and related macrocycles. Display omitted
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