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We designed and synthesized two kinds of spirobifluorene (SP)-based acceptor–donor–acceptor (A–D–A)-type acceptor materials, denoted by SP-IC and SP-TCF, which have an A–D–A structure consisting of a 3D tetrathienospirobifluorene donor core and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC) or 2-(3-cyano-4,5,5-trimethylfuran-2(5H)-ylidene)malononitrile (TCF) acceptors as terminal units, respectively. Their LUMO levels (−3.91 eV for SP-IC and −3.97 eV for SP-TCF) are suitable as n-type molecules for PTB7-Th-based polymer solar cells. However, their morphologies in blend films with a conjugated donor polymer, Poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b]dithiophene]{3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7-Th), exhibited considerable differences. The PTB7-Th:SP-IC blend film exhibited a better-defined nanophase-separated morphology than PTB7-Th:SP-TCF blend film. The corresponding bulk heterojunction polymer solar cell based on PTB7-Th:SP-IC showed four times higher power conversion efficiency (PCE = 4.50%) than that of PTB7-Th:SP-TCF. The higher PCE was well explained by investigating the morphology, which was affected by the surface energy of the acceptor molecules at the donor–acceptor interface.

A phenothiazine-based colorimetric and fluorescent probe ( 3 ) for Hg 2+ and Cu 2+ was designed and synthesized. Probe 3 showed high selectivity and sensitivity toward Hg 2+ and Cu 2+ over other metal ions. This probe works as a chemodosimeter based on the Kucherov reaction for the selective detection of Hg 2+ . Copper recognition is based on soft–soft metal interactions with the –S and –N atoms of the probe 3 . Probe 3 exhibited a red-shift in the absorption spectra from 449 to 606 nm for Hg 2+ and at 612 nm for Cu 2+ that is accompanied by significant color changes from orange to dark blue and blackish-blue. Probe 3 could be used as a solid state (test paper, TLC plates) optical sensor for the selective detection of Hg 2+ and Cu 2+ . The binding process was confirmed by UV–vis absorption, fluorescence measurements, IR, 1 H NMR and mass spectroscopy.

Conjugated polymers are of great interest and have been extensively examined as colorimetric and fluorometric sensors for biologically important species. Here, we report the systematic investigation of diketopyrrolopyrrole based conjugated polymers (PDTDPPT, PDTDPPSe and PDTDPPTe) bearing S, Se, and Te towards oxidative addition of Br2 using absorption spectroscopy, NMR spectroscopy, cyclic voltammetry, atomic force microscopy, and density functional theory calculations. PDTDPPTe polymer displays a highly sensitive, selective, and rapid response to Br2.

In this study, a panchromatic absorptive conjugated terpolymer, BDTID-BDT3MT, is synthesized, which consists of electron-donating benzodithiophene (BDT), isoindigo (ID) as a strong electron-accepting unit, and methyl-3-thiophenecarboxylate (3 MT) as a weak electron-accepting unit. By combining these three monomers into the structure of a conjugated terpolymer, the absorption spectrum of BDTID-BDT3MT is induced to exhibit an unusually broad, strong, and uniform band in the wavelength interval from 300 to 750 nm, which helps achieving highly efficient light harvesting under solar illumination. The intriguing panchromatic absorption behavior of BDTID-BDT3MT was explained on the basis of theoretical calculations using simplified repeating units. Polymer solar cells (PSCs) based on BDTID-BDT3MT as a donating polymer and non-fullerene acceptors (e.g., ITIC-4F) exhibited a high power conversion efficiency (PCE) of 5.38%, high open circuit voltage (Voc) of 0.88 V, and short circuit current density (Jsc) of 13.74 mA/cm2, while PSCs based on ternary blend systems consisting of BDTID, BDT3MT, and ITIC-4F exhibited lower PCE and Jsc of 3.74% and 11.15 mA/cm2, respectively. The superior performance of PSCs based on BDTID-BDT3MT can be attributed to their high light harvesting efficiencies and relatively more favorable nano-phase film morphologies. Our results establish that BDT, ID, and 3 MT units serve as useful building blocks in the structure of conjugated terpolymers due to their remarkably broad panchromatic absorption band.

Two host materials, CzPy2TCz and CzPy3TCz, were designed as structural isomers and synthesized to achieve high efficiency thermally activated delayed fluorescence-organic light emitting diodes (TADF-OLEDs). The design strategy involved introducing a pyridine group into the core structure as an electron-withdrawing unit and varying the substitution position of tercarbazole (TCz). To realize green TADF-OLED, the two host materials synthesized in this study have excellent thermal stability and high excited triplet energy (T1 = 2.95–2.98 eV). The maximum external quantum efficiency and current efficiency values for CzPy2TCz were 23.81% and 80.2 cd/A, respectively and the respective values for CzPy3TCz were 20.27% and 70.1 cd/A, respectively. Structural isomers with carbazole (Cz) and TCz units at the 2,6-position of the pyridine core effectuate better device performance. Consequently, we found that the host materials introduced in this study play an important role in implementing high performing solution-processed green TADF-OLED.

In this work, dendritic luminogens, namely, 3ICz-Tr as a blue emitter and Tri-tNID as an orange-red emitter, were synthesized and used for the application of white organic light-emitting diodes (WOLEDs). These molecules have appropriately high molecular weights, which are favorable for the fabrication of thin films with fine surface morphologies. Interestingly, the blue emitting 3ICz-Tr displays fluorescent character and the orange-red emitting Tri-tNID exhibited thermally activated delayed fluorescence, which was confirmed by steady state and transient photoluminescence (TRPL) spectroscopy. Eventually, WOLED devices could be realized by mixing the two molecules and optimizing their mixture composition. Among the devices we fabricated, the device with Tri-tNID and 3ICz-Tr (0.5:99.5 wt ratio) without additional host material demonstrated nearly pure white emission, with the maximum EQE of 8.32% and CIE coordinate of (0.32, 0.30). Furthermore, by changing the composition of the two dendritic molecules, the emission color can be adjusted from a warm white to a cool white in the corresponding WOLED.

New organic semiconducting molecules containing diketopyrrolopyrrole and thiophene units were designed to investigate the influence of effective conjugation length on the performance of organic photovoltaics made with [6,6]-phenyl-C61-butyric acid methyl ester. New D–A–D–A–D type molecules (where; D = donor, A = acceptor) such as ter- and quarter-thiophene bridged diketopyrrolopyrrole dimers were synthesized with different numbers of conjugative units. The field-effect mobilities of these molecules were determined by fabricating thin film transistors. The new molecules displayed moderately high mobility between 3.6 × 10 −2 and 1.1 × 10 −2 cm 2 V −1 s −1 without a thermal annealing process for TT(BTDPP) 2 and QT(BTDPP) 2 . The TT(BTDPP) 2 molecule possesses a longer effective conjugation length ( c.f . QT(BTDPP) 2 ) and shows a high carrier mobility. When employing the ter- and quarter-thiophene bridged diketopyrrolopyrrole dimers as donor molecule in combination with [6,6]-phenyl-C61-butyric acid methyl ester [TT(BTDPP) 2 :PC 61 BM = 1:0.8 w/w ], the photovoltaic cell provides the highest power conversion efficiency of 3.76%.

A diketopyrrolopyrrole derivative was synthesized and designed with two trimethylsilyl groups to allow for sensitive, selective and fast recognition of fluoride ions by using a chemodosimeter approach. The probe exhibited a blue shift in the absorption and emission spectra in the presence of fluoride ions due to deprotection of the electron donating trimethylsilyl groups in the probe. UV–vis absorption, fluorescence, density functional theory and cyclic voltammetry studies indicated fluoride triggered cleavage of the Si–C bond resulting in the blue spectral shift.

A reversible probe based on diketopyrrolopyrrole–tellurophene conjugate for the detection of reactive oxygen species has been designed and synthesized. The probe utilizes the redox properties of the tellurium atom for the detection of reactive oxygen species and exhibits high selectivity and sensitivity towards H 2 O 2 ; the presence of which is demonstrated by a fluorescent signal. In addition to fluorescence signal, the probe displayed a color change from light blue to light purple upon oxidation by H 2 O 2 in aqueous media. The generated tellurophene-1-oxide may be quickly reduced by glutathione to regenerate the original diketopyrrolopyrrole–tellurophene conjugate. The probe can be applied to monitor the concentration of H 2 O 2 in aqueous solution over an approximate pH range 3.8–8.0.

We designed and synthesized a series of phenothiazine-based donor–acceptor type molecules which consist of different numbers of chromophores in a molecule for use as photosensitizers for dye-sensitized solar cells (DSSCs). Intriguingly, a dendritic molecule containing three chromophores not only gave a new possibility to modify the three dimensional structure, but also reduced aggregation between chromophores inducing dipole–dipole interaction. The DSSCs made of a dendritic photosensitizer system exhibited much higher cell efficiencies than those with the single- or double-chromophoric photosensitizers due to efficient electron extraction pathways in the dendritic molecule which lead to a significantly reduce recombination rate of electrons from the TiO2 to the electrolyte when the same numbers of chromophores were loaded on the TiO2 surface. In particular, the DSSC based on the dendritic molecule exhibited improved open-circuit voltage than that of the single- or double-chromophoric photosensitizers. This can be attributed to strong adsorption properties of the TiO2 electrode and a screening effect to the electrolyte ions provided by the network structure of the dendritic photosensitizer. The different behavior of these DSSCs was explained by comparing the results of electrochemical impedance spectroscopy and measurement of open-circuit voltage decay.

9-((6-Phenylpyridin-3-yl)methyl)-9H-carbazole and 9-((6-(4-fluorophenyl)pyridin-3-yl)methyl)-9H-carbazole were synthesized as ligands by attaching a carbazolyl group to the pyridine in 2-phenylpyridine and 2-(4-fluorophenyl)pyridine, respectively. Four different Ir(III) complexes were prepared using a simple procedure, the solubility of which was significantly greater than that of conventional green-emitting Ir(ppy)3. Among the many devices fabricated, that which contained 10% of Ir(Cz-ppy)1(Cz-Fppy)2 in PVK/PBD (70:30 wt%), exhibited an external quantum efficiency of 6.80%, luminous efficiency of 20.23 cd/A, and maximum brightness of 17520 cd/m2. In particular, the electronic property of the new 9-((6-(4-fluorophenyl)pyridin-3-yl)methyl)-9H-carbazole ligand can manipulate the triplet energy level of the Ir(III) complex to finely tune the emission spectra.

The ligands, 9-((6-phenylpyridin-3-yl)methyl)- 9H -carbazole and 9-(4-(pyridin-2-yl)benzyl)- 9H -carbazole were synthesized by attaching a carbazolyl group to the pyridine and phenyl rings of 2-phenylpyridine, respectively. Ir(III) complexes were prepared by a simple procedure and the solubility of the novel complexes was significantly better than that of the conventional, green-emitting conventional fac -tris(2-phenylpyridinato-C 2 ,N)iridium(III). The Ir(III) complexes were used to prepare electrophosphorescent polymer light-emitting devices. The device comprising 10% of fac -tris(2-(4′-((9 H -carbazol-9-yl)methyl)phenyl)pyridinato-C 2 ,N)iridium(III) exhibited an external quantum efficiency of 7.88%, luminous efficiency of 23.01 cd/A, and maximum brightness of 32,640 cd/m 2 . The color of the emissions of fac -tris(2-(4′-((9 H -carbazol-9-yl)methyl)phenyl)pyridinato-C 2 ,N)iridium(III) was similar to that of conventional fac -tris(2-phenylpyridinato-C 2 ,N)iridium(III). This work shows that integration of a rigid hole-transporting carbazole and phosphorescent complex in one molecule provides a new route to highly efficient, solution-processable complexes for electrophosphorescent applications.

Novel, photocrosslinkable, star-shaped molecules have been synthesized by attaching a tricyanopyrroline (TCP)-based chromophore to 6-(4-{1,1-bis-[4-(5-carboxy-pentyloxy)-phenyl]-ethyl}-phenoxy)-hexanoic acid. The chromophore 2-(3-cyano-4-(4-diethylamino-phenyl)-5-oxo-1-{4-[4-(3-oxo-3-phenyl-propenyl)-phenoxy]-butyl}-1,5-dihydro-pyrrol-2-ylidene)-malononitrile is a second-order nonlinear optical active compound and bears a chalcone moiety that is sensitive to UV light ( λ = 320–350 nm) for 2π + 2π photocycloaddition. The resultant molecules exhibited good processability and showed 29–37 pm/V of the maximum electro-optic coefficient at 1300 nm.