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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(28):8270-8274
The double perovskite family, A2MIMIIIX6, is a promising route to overcome the lead toxicity issue confronting the current photovoltaic (PV) standout, CH3NH3PbI3. Given the generally large indirect band gap within most known double perovskites, band‐gap engineering provides an important approach for targeting outstanding PV performance within this family. Using Cs2AgBiBr6 as host, band‐gap engineering through alloying of InIII/SbIII has been demonstrated in the current work. Cs2Ag(Bi1−x Mx )Br6 (M=In, Sb) accommodates up to 75 % InIII with increased band gap, and up to 37.5 % SbIII with reduced band gap; that is, enabling ca. 0.41 eV band gap modulation through introduction of the two metals, with smallest value of 1.86 eV for Cs2Ag(Bi0.625Sb0.375)Br6. Band structure calculations indicate that opposite band gap shift directions associated with Sb/In substitution arise from different atomic configurations for these atoms. Associated photoluminescence and environmental stability of the three‐metal systems are also assessed. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(41):12832-12836
The alloying behavior between FAPbI3 and CsSnI3 perovskites is studied carefully for the first time, which has led to the realization of single‐phase hybrid perovskites of (FAPbI3)1−x (CsSnI3)x (0<x <1) compositions with anomalous bandgaps. (FAPbI3)1−x (CsSnI3)x perovskites exhibit stable, homogenous composition/microstructure at the nanoscale, as confirmed by microscopic characterization. The ideal bandgap of 1.3 eV for single‐junction solar cell operation is achieved in the rationally‐tailored (FAPbI3)0.7(CsSnI3)0.3‐composition perovskite. Solar cells based on this new perovskite show power conversion efficiency up to 14.6 %. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(2):500-504
Vacancy‐rich layered materials with good electron‐transfer property are of great interest. Herein, a full‐spectrum responsive vacancy‐rich monolayer BiO2−x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO2−x is responsible for the enhanced photon response and photo‐absorption, which were confirmed by UV/Vis‐NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO2−x, monolayer BiO2−x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near‐infrared light (NIR) irradiation, which can be attributed to the vacancy VBi‐O′′′ as confirmed by the positron annihilation spectra. The presence of VBi‐O′′′ defects in monolayer BiO2−x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(35):11383-11387
Low‐toxicity, air‐stable bismuth‐based perovskite materials are attractive substitutes for lead halide perovskites in photovoltaic and optoelectronic devices. The structural, optical, and electrical property changes of zero‐dimensional perovskite Cs3Bi2I9 resulting from lattice compression is presented. An emission enhancement under mild pressure is attributed to the increase in exciton binding energy. Unprecedented band gap narrowing originated from Bi−I bond contraction, and the decrease in bridging Bi‐I‐Bi angle enhances metal halide orbital overlap, thereby breaking through the Shockley–Queisser limit under relatively low pressure. Pressure‐induced structural evolutions correlate well with changes in optical properties, and the changes are reversible upon decompression. Considerable resistance reduction implies a semiconductor‐to‐conductor transition at ca. 28 GPa, and the final confirmed metallic character by electrical experiments indicates a wholly new electronic property. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(11):3091-3095
The design of narrow band gap (NBG) donors or acceptors and their application in organic solar cells (OSCs) are of great importance in the conversion of solar photons to electrons. Limited by the inevitable energy loss from the optical band gap of the photovoltaic material to the open‐circuit voltage of the OSC device, the improvement of the power conversion efficiency (PCE) of NBG‐based OSCs faces great challenges. A novel acceptor–donor–acceptor structured non‐fullerene acceptor is reported with an ultra‐narrow band gap of 1.24 eV, which was achieved by an enhanced intramolecular charge transfer (ICT) effect. In the OSC device, despite a low energy loss of 0.509 eV, an impressive short‐circuit current density of 25.3 mA cm−2 is still recorded, which is the highest value for all OSC devices. The high 10.9 % PCE of the NBG‐based OSC demonstrates that the design and application of ultra‐narrow materials have the potential to further improve the PCE of OSC devices. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(50):16185-16189
Novel inorganic lead‐free double perovskites with improved stability are regarded as alternatives to state‐of‐art hybrid lead halide perovskites in photovoltaic devices. The recently discovered Cs2AgBiBr6 double perovskite exhibits attractive optical and electronic features, making it promising for various optoelectronic applications. However, its practical performance is hampered by the large band gap. In this work, remarkable band gap narrowing of Cs2AgBiBr6 is, for the first time, achieved on inorganic photovoltaic double perovskites through high pressure treatments. Moreover, the narrowed band gap is partially retainable after releasing pressure, promoting its optoelectronic applications. This work not only provides novel insights into the structure–property relationship in lead‐free double perovskites, but also offers new strategies for further development of advanced perovskite devices. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(3):824-829
Photonic crystals are expected to be metamaterials because of their potential to control the propagation of light in the linear and nonlinear regimes. Biological single‐network, triply periodic constant mean curvature surface structures are considered excellent candidates owing to their large complete band gap. However, the chemical construction of these relevant structures is rare and developing new structures from thermodynamically stable double‐network self‐organizing systems is challenging. Herein, we reveal that the shifted double‐diamond titania scaffold can achieve a complete band gap. The largest (7.71 %) band gap is theoretically obtained by shifting 0.332 c with the dielectric contrast of titania (6.25). A titania scaffold with similar shifted double‐diamond structure was fabricated using a reverse core–shell microphase‐templating system with an amphiphilic diblock copolymer and a titania source in a mixture of tetrahydrofuran and water, which could result in a 2.05–3.78 % gap. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(40):12408-12412
The encapsulation of viologen derivatives into metallic single‐walled carbon nanotubes (SWNTs) results in the opening of a band gap, making the SWNTs semiconducting. Raman spectroscopy, thermogravimetric analysis, and aberration‐corrected high‐resolution transmission electron microscopy confirm the encapsulation process. Through the fabrication of field‐effect transistor devices, the change of the electronic structure of the tubes from metallic to semiconducting upon the encapsulation is confirmed. The opening of a gap in the band structure of the tubes was not detected in supramolecular controls. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(41):12818-12822
Although face‐centered cubic (fcc), body‐centered cubic (bcc), hexagonal close‐packed (hcp), and other structured gold nanoclusters have been reported, it was unclear whether gold nanoclusters with mix‐packed (fcc and non‐fcc) kernels exist, and the correlation between kernel packing and the properties of gold nanoclusters is unknown. A Au49(2,4‐DMBT)27 nanocluster with a shell electron count of 22 has now been been synthesized and structurally resolved by single‐crystal X‐ray crystallography, which revealed that Au49(2,4‐DMBT)27 contains a unique Au34 kernel consisting of one quasi‐fcc‐structured Au21 and one non‐fcc‐structured Au13 unit (where 2,4‐DMBTH=2,4‐dimethylbenzenethiol). Further experiments revealed that the kernel packing greatly influences the electrochemical gap (EG) and the fcc structure has a larger EG than the investigated non‐fcc structure. 相似文献
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Ana Snchez‐Grande Bruno de&#x;la&#x;Torre Jos Santos Borja Cirera Koen Lauwaet Taras Chutora Shayan Edalatmanesh Pingo Mutombo Johanna Rosen Radek Zbo&#x;il Rodolfo Miranda Jonas Bjrk Pavel Jelínek Nazario Martín David cija 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6631-6635
Engineering low‐band‐gap π‐conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on‐surface synthesis protocol to overcome such difficulties and produce poly(p‐anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400 K, resulting in anthracene‐based polymers. High‐resolution nc‐AFM measurements confirm the nature of the ethynylene‐bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface‐stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design π‐conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on‐surface synthesis. 相似文献
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Ana Snchez‐Grande Bruno de&#x;la&#x;Torre Jos Santos Borja Cirera Koen Lauwaet Taras Chutora Shayan Edalatmanesh Pingo Mutombo Johanna Rosen Radek Zbo&#x;il Rodolfo Miranda Jonas Bjrk Pavel Jelínek Nazario Martín David cija 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6853-6853
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Kyu Hyung Park Pyosang Kim Woojae Kim Hideyuki Shimizu Minwoo Han Eunji Sim Masahiko Iyoda Dongho Kim 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(43):12902-12906
Excited‐state dynamic planarization processes play a crucial role in determining exciton size in cyclic systems, as reported for π‐conjugated linear oligomers. Herein, we report time‐resolved fluorescence spectra and molecular dynamics simulations of π‐conjugated cyclic oligothiophenes in which the number of subunits was chosen to show the size‐dependent dynamic planarization in the vicinity of a ring‐to‐linear behavioral turning point. Analyses on the evolution of the total fluorescence intensity and the ratio between 0–1 to 0–0 vibronic bands suggest that excitons formed in a cyclic oligothiophene composed of six subunits fully delocalize over the cyclic carbon backbone, whereas those formed in larger systems fail to achieve complete delocalization. With the aid of molecular dynamics simulations, it is shown that distorted structures unfavorable for efficient exciton delocalization are more easily populated as the size of the cyclic system increases. 相似文献