•A newly planar geometry of dithiafulvene sensitizer DTF-C4 was synthesized.•Formation of J-aggregates of DTF-C4 on TiO2 by rinsing with a poor solvent acetonitrile.•Increasing the J-aggregates of DTF-C4 on TiO2 lead to uplift PCE to 7.48% and Voc above 850 mv.•J-aggregates of DTF-C4 enhanced light harvesting ability and retarded electron recombination.A newly planar dithiafulvene sensitizer (DTF-C4) trending to form J-aggregates on the surface of mesoporous TiO2 by simply rinsing with a poor solvent acetonitrile was synthesized. We further show that the self-assembled J-aggregates optimized the TiO2 surface utilization, enhanced the light harvesting ability by broadening and red-shifting the absorption, and suppressed the electron recombination, thereby significantly promoting the solar cell efficiency. Compared to the photoanode surface modified with DTF-C4 and the classical coadsorbent chenodeoxycholic acid (CDCA), the DSC based the DTF-C4 compact J-aggregates exhibited a dramatically improved performance without the loss of adsorbed dyes, uplifting the power conversion efficiency from 4.68% to 7.48% alongside with a high open-circuit voltage of above 850 mV, which is higher than that of the commercial N719-based cell (770 mv).The self-assembled J-aggregates of a newly synthesized planar dithiafulvene sensitizer optimized the TiO2/dye interface, uplifting the power conversion efficiency from 4.68% to 7.48% alongside with a high open-circuit voltage of above 850 mV.

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.

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.

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.

Two hole transporting materials (HTMs), SFX-PT1 and SFX-PT2, were designed and synthesized by combing a spiro[fluorene-9, 9′-xanthene] (SFX) core with tetra- phenothiazine substituted at the 2,2′,7,7′- and 2,3′,6,′7-positions, respectively. As comparison, a HTM with tetra-phenothiazine substituted at the 2,2′,7,7′-positions of a 9, 9′-spirobifluorene core (Spiro-PT) was also synthesized. Their photophysical and electrochemical properties, thermal stability and hole mobility were investigated. It was demonstrated that SFX-centered HTMs exhibited superior Stokes shift, thermal stability and hole mobility than those of Spiro-PT. Combining with the substituted positions modification, SFX-PT1 has the largest Stokes shift of 197 nm, the highest decomposition temperature of 435 °C and hole mobility of 2.08 × 10−3 cm2V−1S−1. Moreover, the energy levels of the HTMs were matched very well with that of CH3NH3PbI3. Our results indicated that SFX-centered, phenothiazole substituted HTMs might be potential candidates for efficient perovskite solar cells.Download high-res image (287KB)Download full-size image

•Two tetra-carbazole substituted spiro[fluorene-9,9′-xanthene] derivatives SFX-Cr1 and SFX-Cr2 were synthesized.•Carbazole substituted positions influenced Tg and hole mobility significantly.•Both of SFX-Cr1 and SFX-Cr2 showing higher thermal stability and hole mobility than NPB.•EQE values of 15.9% and 16.3% were obtained in SFX-Cr1 and SFX-Cr2-based OLEDs.Two spiro[fluorene-9,9′-xanthene]-centered (SFX), tetra-carbazole substituted molecules 2,2′,7,7′-tetrakis(N, N-carbazole)-spiro(fluorene-9,9′-xanthene) (SFX-Cr1) and 2,3′,6,′7-tetrakis(N, N-carbazole)-spiro(fluorene-9,9′-xanthene) (SFX-Cr2) were synthesized, and the effect of the position of carbazole substitutes on bulk properties, such as photophysical and electrochemical properties, thermal stability and hole mobility were investigated. The results implied both these two materials have excellent thermal stability and hole mobility than those of N, N′-Bis(naphthalen-1-yl)N, N′-bis(phenyl)-benzidine (NPB). To explore the application, organic light-emitting diodes (OLEDs) with SFX-Cr1 and SFX-Cr2 as hole transport layer were fabricated and characterized. SFX-Cr2 garnered the highest glass transition temperature of 130.1 °C and hole mobility of 1.57 × 10−3 cm2 V−1 S−1, yielding an appreciated OLED performance in terms of a maximum current efficiency of 55.8 cd A−1, a maximum power efficiency of 46.6 l m W−1, and a maximum external quantum efficiency of 16.3%.Two tetra-carbazole substituted spiro[fluorene-9,9′-xanthene] derivatives are demonstrated as efficient hole transport materials exhibiting a peak external quantum efficiency of 16.3% in OLEDs.Download high-res image (173KB)Download full-size image

Two slightly twisted A–π–D–π–A molecules were prepared to demonstrate that the red/near-infrared mechanoresponsive luminescence turn-on behaviors could be realized through mechanically disturbing their weakly/non-emissive metastable nanostructures, giving emissive amorphous aggregates with λem = 620 nm, ΦF = 12% (h-DIPT) and λem = 700 nm, ΦF = 10% (DIPT), respectively.

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%.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%.

•Linear thiophene-containing π-conjugated aldehydes with aggregation-induced emission characteristic are studied.•Amorphous nanoscale aggregates exhibit distinct aggregation-induced emission behavior.•Efficient solid red luminophor is achieved from the linear AIE aldehyde.Two linear thiophene-containing π-conjugated aldehydes 4-(thiophen-2-yl)benzaldehyde and 2,5-bis[4-(formyl)phenyl]thiophene exhibiting aggregation-induced emission (AIE) were demonstrated. The photophysical properties of the two aldehydes in solution and THF/H2O mixtures were studied, and aggregates formed with different water fractions were studied by scanning electron microscopy. Results indicated that amorphous nanoscale aggregates exhibit distinct AIE behavior when assembled in solutions with appropriate water contents. Condensation of 1,3-indandione with 4-(thiophen-2-yl)benzaldehyde generated a new luminophor 2-[4-(thiophen-2-yl)benzylidene]-2H-indene-1,3-dione; this product presents as a solid powder that emits intensely red photoluminescence at 620 nm with a quantum yield of 12.8%.Two linear thiophene-containing π-conjugated aldehydes 4-(thiophen-2-yl)benzaldehyde and 2,5-bis[4-(formyl)phenyl]thiophene exhibiting aggregation-induced emission (AIE). Our preliminary work shows that these aldehydes have potential applications in building solid red luminophors.

From the viewpoint of practical application, organic materials that are emissive in aggregate or solid state have been a hot research topic. This work demonstrates that 2,2′:5′,2″-terthiophene-5-carbaldehyde (TTA) exhibited aggregation-induced emission (AIE) property. The photophysical properties of the aldehyde in THF/H2O mixtures were studied, and the aggregates formed with different water fractions were studied by scanning electron microscopy. Our results indicated that the presence of an electron deficient aldehyde group as the end-capped group should endow TTA with AIE characteristic. Furthermore, ordered nanoscale aggregates of TTA exhibited distinct AIE behavior when assembled in solutions with appropriate water content.2,2′:5′,2″-Terthiophene-5-carbaldehyde exhibited aggregation-induced emission (AIE) property in THF/H2O mixtures with appropriate water content, which can be attributed to the presence of aldehyde group and formed ordered nanoscale aggregates.

•A novel π-extended tetrathiafulvene derivative DPD was synthesized via a facile approach at first time.•The DPD exhibits enhanced emission in solid film.•The AIEE mechanism of DPD can be attributed to the formed excimer state of DPD and J-aggregates in solid state.Solid-state emissive organic materials have received increasing attention due to their prospective applications in large-area. Here, a novel π-extended tetrathiafulvene derivative DPD with donor-π-donor structure has been newly developed to produce the prominent characteristic of aggregation-induced enhanced emission (AIEE) that exhibits higher fluorescence quantum efficiency in solid film compare to its solutions. The AIEE mechanism of DPD was studied in detail through photophysical investigations and can be dominant attributed to the formed excimer state of DPD and J-aggregates in solid state.

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.

Two slightly twisted A–π–D–π–A molecules were prepared to demonstrate that the red/near-infrared mechanoresponsive luminescence turn-on behaviors could be realized through mechanically disturbing their weakly/non-emissive metastable nanostructures, giving emissive amorphous aggregates with λem = 620 nm, ΦF = 12% (h-DIPT) and λem = 700 nm, ΦF = 10% (DIPT), respectively.