Kunpeng Guo

Dithiafulvenyl unit as a new donor for high-efficiency dye-sensitized solar cells: synthesis and demonstration of a family of metal-free organic sensitizers.

This work identifies the dithiafulvenyl unit as an excellent electron donor for constructing D-π-A-type metal-free organic sensitizers of dye-sensitized solar cells (DSCs). Synthesized and tested are three sensitizers all with this donor and a cyanoacrylic acid acceptor but differing in the phenyl (DTF-C1), biphenyl (DTF-C2), and phenyl-thiopheneyl-phenyl π-bridges (DTF-C3). Devices based on these dyes exhibit a dramatically improved performance with the increasing π-bridge length, culminating with DTF-C3 in η = 8.29% under standard global AM 1.5 illumination.

Porphyrin-based metallopolymers: synthesis, characterization and pyrolytic study for the generation of magnetic metal nanoparticles

Metallopolymers with different metal centers, pendant groups and linkages exhibit diverse structures and properties, thus giving rise to versatile applications, e.g., as emissive and photovoltaic materials, optical limiters, materials for nano-electronics, information storage, nanopatterning and sensing, macromolecular catalysts and artificial enzymes, and stimuli-responsive materials. Recently, metallopolymers as precursors to generate monometallic or metal alloy nanoparticles are of great interest owing to their advantages of ease of processability, atomic level mixing, and stoichiometric control over composition. By taking advantage of the template effect of porphyrin compounds, a series of monometallic and heterobimetallic polymers are synthesized which are characterized by NMR, IR, HRMS, EA, GPC and TGA, respectively. Photophysical properties of these metallopolymers are also studied by UV-vis spectroscopy. Pyrolytic treatment of these metallopolymers generates various magnetic monometallic and metal alloy nanoparticles which can be used in data storage, catalysis, biomedicine, etc.

A–π–D–π–A carbazole derivatives with remarkable solvatochromism and mechanoresponsive luminescence turn-on

Two A–π–D–π–A molecules with a carbazole donor and a dicyanovinyl acceptor but differing in N-hexyl (h-CPDM) and N-isooctyl substituents (i-CPDM) were synthesized, and both of them presented remarkable dual properties of solvatochromism and mechanoresponsive luminescence (MRL) turn-on. The intrinsic intramolecular charge transfer (ICT) characteristic endowed both luminophors with a prominent solvatochromic effect, with emission color tuning from blue to orange-red by changing the solvent from nonpolar hexane to polar dimethyl sulfoxide. Meanwhile, the non-/weakly emissive original powders of h-CPDM and i-CPDM gave bright orange (610 nm) and yellow (596 nm) emission with the photoluminescence quantum yields increasing as high as 85-fold after being ground. Investigations revealed this mechanoresponsive luminescence turn-on could be ascribed to the disturbance of the π–π stacking interactions in the non-/weakly emissive J-aggregates by mechanical force. This work offers carbazole derivatives that can be used as sensitive fluorescent indicators for organic solvents and mechanical sensors.

Microwave-assisted hydrothermal synthesis of solid-state carbon dots with intensive emission for white light-emitting devices

A one-pot microwave-assisted hydrothermal approach was developed to quickly synthesize organosilane-functionalized carbon dots (Si-CDs) within 5 minutes. With the assistance of N-(β-aminoethyl)-γ-aminopropyl trimethoxysilane (KH-792) as distance barrier chains, aggregation-caused quenching is suppressed successfully, which contributes to the emission of bright blue fluorescence by solid-state Si-CDs (λem ∼ 454 nm). The photoluminescence quantum yield of the as-prepared Si-CDs in the solid state reaches 65.8% with an optimized molar ratio of the reactant citric acid to KH-792 of 1 : 5 and a reaction temperature of 180 °C, which is 2.5-fold that of their solution. Together with their good film-forming ability and thermal stability, Si-CDs were applied to fabricate a white-light-emitting device with color coordinates of (0.32, 0.36) and a correlated color temperature of 6071 K. Our results indicate that the as-prepared Si-CDs are promising materials with efficient solid-state emission to be used in lighting, backlight displays and other optoelectronic devices.

Molecular engineering of dithiafulvene organic sensitizers with pyridine acceptor for high efficiency dye-sensitized solar cells

Donor-π-acceptor (D-π-A) organic compounds have drawn keen interests as photosensitizers in dye sensitized solar cells (DSSCs). Recent studies showed that pyridine ring as an electron-withdrawing anchoring group could lead to efficient electron injection. To improve the performance of pyridine containing sensitizers based DSSCs, the electron donor, π-bridge and the whole structure should be well engineered at molecular level. In this work, we prepared two monomer type dithiafulvene based sensitizers both with a pyridine acceptor but differing in the phenyl-thienyl (DTFPy3) and thienyl-phenyl π-bridges (DTFPy4), and two corresponding dimeric congeners D-DTFPy3 and D-DTFPy4, and tested them in DSSCs. It was found that the arrangement of the electron-rich thienyl group adjacent to the electron donor moiety in the π-bridge red-shifted in the absorption, and the dimeric sensitizers exhibited significantly enhanced absorption. Among them, D-DTFPy4 garnered the highest light harvesting efficiency, yielding an overall power conversion efficiency up to 5.26%.摘要近年来, 具有给体-π桥-受体结构的有机化合物作为光敏剂用于染料敏化太阳电池的研究引起广泛关注. 研究发现吡啶作为电子受体和吸附基团时可实现有效的电子注入. 为了提高含吡啶受体有机敏化剂的性能, 需要通过分子工程对电子给体, π桥和分子结构在分子层面上进行优化. 本研究以二硫富瓦烯为电子给体, 吡啶为电子受体, 合成了两个π桥结构分别为噻吩-苯和苯-噻吩的单体型敏化剂DTFPy3和DTFPy4, 对二者及其对应的二聚体型敏化剂D-DTFPy3和D-DTFPy4的研究发现, 调整π桥上富电子噻吩靠近给体一端时可使敏化剂的吸收波长红移. 另外, 二聚体型敏化剂可有效提高敏化剂的吸光强度. 在这四个敏化剂中, D-DTFPy4表现出最佳的光捕获效率, 以其制备的染料敏化太阳电池, 光电转换效率可达5.26%.