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The self-terminated, layered structure of van der Waals materials introduces fundamental advantages for infrared (IR) optoelectronic devices. These are mainly associated with the potential for low noise while maintaining high internal quantum efficiency when reducing IR absorber thicknesses. In this study, we introduce a new van der Waals material candidate, zirconium germanium telluride (ZrGeTe4), to a growing family of promising IR van der Waals materials. We find the bulk form ZrGeTe4 has an indirect band edge around ∼0.5 eV, in close agreement with previous theoretical predictions. This material is found to be stable up to 140 °C and shows minimal compositional variation even after >30 days storage in humid air. We demonstrate simple proof-of-concept broad spectrum photodetectors with responsivities above 0.1 AW-1 across both the visible and short-wave infrared wavelengths. This corresponds to a specific detectivity of ∼109 cm Hz1/2 W-1 at λ = 1.4 μm at room temperature. These devices show a linear photoresponse vs illumination intensity relationship over ∼4 orders of magnitude, and fast rise/fall times of ∼50 ns, also verified by a 3 dB roll-off frequency of 5.9 MHz. As the first demonstration of photodetection using ZrGeTe4, these characteristics measured on a simple proof-of-concept device show the exciting potential of the ZrGeTe4 for room temperature IR optoelectronic applications.

Fingerprints remain topologically unchanged in one's whole life, and therefore, have been used as a means to biometrically identify individuals in forensic investigations, law enforcement and access control. Appropriate methods are essential to obtain high-quality fingerprint images. In this contribution, an aggregation-induced emission luminogen tetraphenylethene-based dye FLA-2 was synthesized and characterized for the visualization of latent fingerprints (LFPs). LFPs can be directly visualized by incubating with the dye FLA-2 solution. And, after a cyanoacrylate fuming method pre-treatment stage, fine fingerprint structures can be obtained from level-1 to level-3 details. Two methods were compared using resolution, fluorescence intensity, and scanning electron microscopy imaging to investigate the influence of the cyanoacrylate fuming method pre-treatment stage. Furthermore, the visualization of old LFPs (7 d, 16 d and 30 d) on glass slides, aluminum foil and coin substrates also became effective after the pre-treatment step. The fluorescent LFP images mentioned above were all validated by using an automated fingerprint identification system obtaining positive matches. These results demonstrate the potential of this method to be applied to visualizing LFPs in the field of public security.

A series of conjugated donor–acceptor (D–A) block copolymers (BCPs) were synthesised using a one-pot Stille coupling polycondensation reaction. This involved reaction between a series of mono-bromo-functionalised Poly3-hexylthiophene (P3HT) polymers (P3HT-Br, Mn : 17, 21 and 43 kg/mol) and [N, N′-bis(2-decyl-tetradecyl)-1,7-dibromo-3,4,9,10-perylene diimide (PBI) and [2,5-bis(trimethylstannyl)-thiophene] (T) monomers. Purification using preparative gel permeation chromatography (GPC) removed any excess P3HT and resulted in BCPs with low polydispersity index values. The P3HT-b-PBIT BCPs were characterised using 1H-NMR and Fourier-transform infrared spectroscopy. When compared to a P3HT/PBIT polymer blend, the D–A BCP films exhibited a remarkably fine structure with a nanoscale morphology. These results indicated that these D–A BCPs have the potential for use as nanostructured active layers in polymer solar cells.

All-conjugated donor-acceptor block copolymers (BCP) were synthesized in a one-pot reaction by a Stille coupling polycondensation through a terminal functional polymer copolymerization process. Mono bromo end-functionalized P3HT samples with various molecular weights (P3HT-Br, Mn: 5, 9, and 26 kg/mol) were copolymerized with AA (N,Nʹ-Bis(2-decyl-1-tetradecyl)-2,6-dibromonaphthalene-1,4,5,8-tetracarboxylic acid bisimide, NDI) and BB (5,5′-bis(trimethylstannyl)-2,2′-bithiophene) type monomers. Further purification by preparative GPC removed excess P3HT to yield block copolymers of low polydispersities with different donor and acceptor block chain lengths. The block copolymers were characterized by 1H-NMR and UV–vis absorption and FTIR spectroscopy. The optical properties, film morphologies, and optoelectronic properties of the block copolymer were strongly influenced by the donor and acceptor block chain lengths. Furthermore, the fully conjugated D-A block copolymer films exhibited fine structures, smooth film morphologies, and better OPV performance than those features of P3HT/PNDIT2 polymer blends. In polymer solar cells based on the various block copolymer as active layers, the device power convention efficiency was improved by maintaining the acceptor block content at 40–50 kg/mol and increasing the P3HT chain from 5 to 26 kg/mol.

Direct C-H arylation is an approximate tool for synthesis of thiophene-diketopyrrolopyrrole (DPP) derivatives, because of better atomic economy, fewer synthetic steps and being environmental friendly. In this work, DPP containing linear structured small molecule TBT(DPPT2)2 are facilely synthesized in high yield by the C-H direct arylation, other small molecule TBT(DPP)2 are synthesized thought stille cross-crouping reaction. Thermal, optimized geometries, electrochemical, photo-physical properties and film morphology of two materials are studied and solution-coated organic field effect transistors (OFETs) are preparated. TBT(DPPT2)2 have wider band gaps and enhanced electronic defects compare to TBT(DPP)2. Both TBT(DPP)2 and TBT(DPPT2)2 demonstrated typical p-type transport with average hole mobility of 1.26 × 10−3 and 9.58 × 10-4 cm2 V-1 s-1 respectively.

By introducing various low concentrations of Iridium complexes to the famous donor polymer of PTB7-Th backbone, new heavy metal containing terpolymers have been demonstrated. When blended with PC71BM, an obvious increase of power conversion efficiency (PCE) is obtained in 1 mol% Ir containing polymer for different photovoltaic devices either using Ca or PDIN as cathode interface layers. The impact of molecular weight on the photovoltaic performance has been particularly considered by using three batches of control polymer PTB7-Th to ensure a fair and more convincing comparison. At similar molecular weight conditions (Mn: ~60 kg mol−1, Mw: 100–110 kg mol−1), the 1 mol% Ir containing PTB7-ThIr1/PC71BM blends exhibits enhanced PCE to 9.19% compared with 7.92% of the control PTB7-Th. Through a combination of physical measurement, such as optoelectrical characterization, GIWAXS and pico-second time-resolved photoluminescence, the enhancement are contributed from comprehensive factors of higher hole mobility, less bimolecular recombination and more efficient slow process of charge separation. Only 1 mol% of Ir complex can do the trick to greatly enhance the efficiency of PTB7-Th: fullerene polymer solar cell from 7.9 to 9.2%. A collaborative research led by Youtian Tao from Nanjing Tech University, China shows that the power conversion efficiency of PTB7-Th: fullerene polymer solar cell can be enhanced by conjugating extremely low ratio of heavy metal Ir complex via ancillary ligand. The conclusions have proved robust for PTB7-Th with different molecular weight, different Ir complex concentrations and different cathode interface materials such as calcium or PDIN. These results prove the importance of heavy metal complex for highly efficient photovoltaic devices and demonstrate a promising design approach toward more efficient photovoltaic polymer donor materials.

We synthesized a rhodamine-based fluorescent probe 1 , which could be used for the optical detection of Fe 3+ . Compared with other commonly coexistent metal ions in aqueous system, it exhibited high sensitivity and selectivity for Fe 3+ , and the detection limit was only 4.2 × 10 −8 M. In addition, the rapid enhancement of fluorescence intensity on addition of Fe 3+ provided a good method for the detection of Fe 3+ . What’s more, the colour change was visible and distinct, so it could be used for the naked-eye detection of Fe 3+ . Furthermore, the fluorescent probe was proved to be effective when used for sensing Fe 3+ in living cells and zebrafish. These results showed its values in biological aspects.

A tetraphenylethene-based dye (FLA-1) was used to develop for enhancing the visualization of the latent fingerprints on the surfaces of various substrates. The resolution of the fingerprints visualized by the probe FLA-1 is enough to offer a positive match according to the information supplied from a police database. Experimental results confirm the accuracy of using the probe for LFPs detection.

A series of novel hyperbranched polymers (HBPs) consisting of a 2,7-subsituted 9-(heptadecan-9-yl)-9H-carbazole unit (A2+A2’) and a tetra-substituted green thermally activated delayed fluorescence (TADF) dye of 2,3,5,6-tetra(9H-carbazol-9-yl)-4-pyridinecarbonitrile (4CzCNPy, B4) have been synthesized via Suzuki cross-coupling reaction following an “A2+A2’+B4” method. The polymers are named according to the polymerization ratio of 4CzCNPy monomer (5 mol%, 10 mol% and 15 mol% for HBPs of P2−P4 respectively, and 0 mol% for the control linear polymer P1). Their thermal, optoelectronic and electrochemical properties have been characterized by a combination of techniques. All the polymers exhibit high thermal stability with the decomposition temperatures (Td) above 400 °C and glass transition temperatures (Tg) up to 98 °C. Unfortunately, the incorporation of TADF moiety into these HBP materials induced non-TADF characteristics. However, when the HBPs functionalized as the host for our previously developed 4CzCNPy TADF dopant in solution processed devices, maximum external quantum efficiency of 5.7% and current efficiency of 17.9 cd/A have been achieved in P3-based device, which is significantly higher than those of 1.5% and 4.2 cd/A for the linear polymer P1.

Platinum complex was introduced in low ratios (0, 1, 1.5, and 5 mol%) as the third monomer in the conjugated backbone of well-known donor polymer PTB7-Th using a random terpolymer molecular design approach. All polymers showed similar absorption behavior and comparable HOMO/LUMO energy levels due to the small amount of Pt complex used. When blended with PC71BM in polymer solar cells, the power conversion efficiency was enhanced to 8.45% (obtained by the device based on PTB7-ThPt1.5 containing 1.5 mol% Pt) compared with 7.92% for the control PTB7-Th. Notably, the apparently low molecular weight of PTB7-ThPt1.5 (Mn/Mw: 46/70 kg mol−1) compared with that of PTB7-Th (Mn/Mw: 62/97 kg mol−1) ensured a more convincing comparison. Using a combination of physical measurements, such as optoelectrical characterization, grazing incident wide-angle X-ray diffraction (GIWAXS), and picosecond time-resolved photoluminescence, the efficiency enhancement was contributed by the higher hole mobility, less bimolecular recombination, and a more efficient slow charge separation process.

Donor-acceptor (D-A) type fully conjugated block copolymer systems have been rarely reported due to the challenges in synthetic approaches to prepare well-defined low-polydispersity products. In this work, fully conjugated block copolymers are synthesized in a one-pot reaction through Stille coupling polycondensation, by utilizing the end-functional polymer copolymerization method. End-functional P3HT are copolymerized with AA (2,7-dibromo-9-(heptadecan-9-yl)-9H-carbazole) and BB (4,7-bis(5-(trimethylstannyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole, TBT) type monomers, respectively. The orthogonal solubility between the very soluble P3HT donor and the insoluble PCDTBT acceptor block improves the purity of block copolymers as well as distinct nano-scale phase-separation compared with other reports on miscibility of donor and acceptor polymer block. Further purification via preparative GPC is carried out to remove the excess of unreacted P3HT and free PCDTBT as well as to achieve low polydispersity of block copolymers. The chemical structure of the P3HT-b-PCDTBT block copolymers are verified via 1H-NMR, and further confirmed by FTIR spectra. The block copolymer shows broad absorption and moderate optical band gap of 1.8 eV. Furthermore, the fully conjugated block copolymer films exhibit significant fine structures, much smoother film morphology compared to P3HT/PCDTBT polymer blends. By adding a small amount of block copolymer P3HT-b-PCDTBT as a compatibilizer into the bulk-heterojunction of P3HT:PC61BM blends, polymer solar cells with an 8% increase of short circuit current (J sc and 10% increase of power conversion efficiency (PCE) are achieved owing to the improvement of the active-layer film morphology. To the best of our knowledge, this is the first report on donor-acceptor type fully conjugated block copolymer as an effective ternary additive in polymer: fullerene bulk heterojunction solar cells.

The application of heavy-metal complexes in bulk-heterojunction (BHJ) solar cells is a promising new research field which has attracted increasing attention, due to their strong spin–orbit coupling for efficient singlet to triplet intersystem crossing. This review article focuses on recent advances of heavy metal complex containing organic and polymer materials as photovoltaic donors in BHJ solar cells. Platinum–acetylide containing oligomersor and polymers have been firstly illustrated due to the good solubility, square planar structure, as well as the fairly strong Pt–Pt interaction. Then the cyclometalated Pt or Ir complex containing conjugated oligomers and polymers are presented in which the triplet organometallic compounds are embedded into the organic/polymer backbone either through cyclometalated main ligand or the auxiliary ligand. Pure triplet small molecular cyclometalated Ir complex are also briefly introduced. Besides the chemical modification, physical doping of cyclometalated heavy metal complexes as additives into the photovoltaic active layers is finally demonstrated.

Direct (hetero) C–H arylation is an advantageous tool for the synthesis of diketopyrrolopyrrole (DPP) derivatives, because of fewer synthetic steps, better atom economy and being environmentally friendly. Herein, four diketopyrrolopyrrole containing linear structured D–A–π–A–D small molecules Ar(DPPT2)2 are facilely synthesized in high yields of 73–82% through C–H direct arylation, where Ar (from electron-donating 1,4-phenyl, 1,4-naphthyl or 9,10-anthryl to electron-accepting 2,5-pyridyl) is functionalized as the core π-bridge structure, DPP as the arm and bithiophene as end-groups. The dihedral angles between the central aryl rings and DPPT2 arms for the optimized geometries of Ph(DPPT2)2, NA(DPPT2)2 and AN(DPPT2)2 gradually increases from 20.3, 44.7 to 93.1°, respectively, which is 18.7° for the pyridyl cored Py(DPPT2)2. It is found that the optoelectronic properties can be elaborately tuned by variation of the central aryl bridge. Moreover, the coplanarity of the molecules as well as the electronic properties of central Ar units significantly affect the charge transport properties. Ph(DPPT2)2 possessing the best conjugated backbone planarity exhibits the highest hole mobility of 0.12 cm2 V−1 s−1 among the three Ar(DPPT2)2 compounds based on the electron-donating phenyl, naphthyl and anthryl cores, while the electron-withdrawing pyridyl core Py(DPPT2)2 shows a poor hole mobility of 6.47 × 10−4 cm2 V−1 s−1 despite of it having the most planar structure.

The incorporation of aggregation-induced emission (AIE) luminogens provides a molecule with enhanced fluorescent emission in the solid state. A representative AIEgen compound is tetraphenylethene (TPE). A series of new conjugates of quinolone derivatives with TPE units (1a - 1f) was synthesized and characterized. The influence on the photophysics of 1a - 1e with a variety of functional groups was investigated systematically by spectroscopic methods and simulated by density-functional theory calculations. A centrosymmetric compound donor-acceptor-donor-type compound 1f with two TPE moieties proved to be the most promising multifunctional material, it exhibited tri-colored (489–569 nm) fluorescence characteristics in tetrahydrofuran-H2O solution with a different water fraction and intense tri-colored solvatochromic (blue, green, and yellow) behaviors. These compounds could be applied as promising acid-base gas probe based on their evident color switch. Compounds 1a - 1f showed the advantage of being a potential piezochromic material.