Diketopyrrolopyrrole based D-π-A-π-D type small organic molecules as hole transporting materials for perovskite solar cells

Three novel diketopyrrolopyrrole （DPP） based small organic molecules were synthesized as hole transporting materials for perovskite solar cells. The effects of different donors and zr bridges on the performance of perovskite solar cells （PSCs） were discussed. The efficiency of TPADPP-1, TPADPP-2. PTZDPP-2 was 5.10%, 9.85% and 8.16% respectively. Compared to TPADPP-2, the voltage of PTZDPP-2 was higher. Because the electron-donatingability of phenothiazine based donor was larger than that of triphenylamine based donor, the HOMO level of PTZDPP-2 was lower than that of TPADPP-2. The results indicated that the diketopyrrolopyrrole based D-π-A-π-D type small organic molecule might be a promising hole trans- porting material in the perovskite solar cells.

High-efficiency single and tandem fullerene solar cells with asymmetric monofluorinated diketopyrrolopyrrole-based polymer

Design and synthesis of low bandgap(LBG) polymer donors is inevitably challenging and their processability from a non-halogenated solvent system remains a hurdle to overcome in the area of highperformance polymer solar cells(PSCs).Due to a high aggregation tendency of LBG polymers,especially diketopyrrolopyrrole(DPP)-based polymers coupled with bithiophenes in the polymer backbones,their widespread adoption in non-ha logena ted solvent-processed PSCs has been limited.Herein,a novel LBG DPP-based polymer,called PDPP4 T-1 F with asymmetric arrangement of fluorine atom,has been successfully synthesized and showed an outstanding power conversion efficiency(PCE) of 10.10% in a singlejunction fullerene-based PSCs.Furthermore,an impressive PCE of 13.21% has been achieved in a tandem device from a fully non-halogenated solvent system,which integrates a wide bandgap PDTBTBz-2 F polymer in the bottom cell and LBG PDPP4 T-1 F polymer in the top cell.The achieved efficiency is the highest value reported in the literature to date in fullerene-based tandem PSCs.We found that a uniformly distributed interpenetrating fibril network with nano-scale phase separation and anisotropy of the polymer backbone orientation for efficient charge transfer/transport and suppressed charge recombination in PDPP4 T-1 F-based PSCs led to outstanding PCEs in single and tandem-junction PSCs.

N-Aryl diketopyrrolopyrrole derivatives towards organic optical and electronic materials

Diketopyrrolopyrrole(DPP)and related derivatives have drawn great attention due to their applications in organic optical/electronic materials.Progress in these materials is associated with developments in the syntheses of the DPP family.Chemical modification of DPP at nitrogen atom,including N-alkylation and N-arylation,is an effective strategy to improve its physical and chemical properties,such as solubility,optical and semiconducting properties.However,N-arylation of DPPs remains challenging compared to the easily accessible N-alkylation.Herein,the synthesis of N-aryl DPP derivatives and correlatedπ-expanded DPPs are summarized,and their optical/electronic properties are introduced.The future perspectives of N-aryl DPP derivatives are also discussed.

Tetramethylammonium Iodide Additive for Enhancing the Charge Carrier Mobilities of Diketopyrrolopyrrole-Based Conju-gated Polymer in Ambipolar Organic Field-Effect Transistors

Diketopyrrolopyrrole(DPP)is one of the most promising building blocks for constructing polymer semiconductors with high charge-carrier mobilities in organic field-effect transistors(OFETs).In this study,a novel DPP-based conjugated polymer,PDPPy-BDD,was designed and synthesized.The ambipolar field-effect transistor characteristics were realized with the average hole and electron mobilities of 3.5×10^(-3)and 3.07×10^(-2)cm^(2)V^(-1)s^(-1),respectively.Both the hole and electron mobilities could be successfully en-hanced by using a tetramethylammonium iodide(NMe4l)additive.Such an enhancement was attributed to the formation of stronger interchainπ-πstackings,the weakening of the face-on packing orientation in the thin film state,and the higher channel conductivi-ties in the OFETs.

Diketopyrrolopyrrole-based Conjugated Polymers as Representative Semiconductors for High-Performance Organic Thin-Film Transistors and Circuits

Since the first report of diketopyrrolopyrrole(DPP)-based conjugated polymers for organic thin-film transistors(OTFTs),these polymers have attracted great attention as representative semiconductors in high-performance OTFTs.Through unremitting efforts in molecular-structure regulation and device optimization,significant mobilities exceeding 10 cm2·V–1·s–1 have been achieved in OTFTs,greatly promoting the applied development of organic circuits.In this review,we summarize our progress in molecular design,synthesis and solution-processing of DPP-based conjugated polymers for OTFT devices and circuits,focusing on the roles of design strategies,synthesis methods and processing techniques.Furthermore,the remaining issues and future outlook in the field are briefly discussed.

Erratum on “Galactose functionalized diketopyrrolopyrrole as NIR fluorescent probes for lectin detection and HepG2 cell targeting based on aggregation-induced emission mechanism” [Sci. China Chem., 2018, 61: 898–908]

In a recent publication [1],there is a mistake in Scheme 1,in which a propargyl alpha-mannoside was drawn on the arrow in the synthetic step from compounds 8/9 to 10/11. The correct structure should be a propargyl beta-galactoside. Here we provide corrections to Scheme 1.

Solution-grown aligned crystals of diketopyrrolopyrroles(DPP)-based small molecules:Rough surfaces and relatively low charge mobility

Field-effect transistors（FETs） of three diketopyrrolopyrroles（DPP）-based small molecules, 3,6-bis（5-phenylthiophene-2-yl）-2,5-bis（2-ethylhexyl）pyrrolopyrrole-1,4-dione（PDPPP）, 3,6-bis（5-（4-fluorophenyl）thiophene-2-yl）-2,5-bis（2-ethylhexyl）pyrrolo pyrrole-1,4-dione（FPDPPPF） and 3,6-bis（5-（4-n-butylphenyl）thiophene-2-yl）-2,5-bis（2-ethylhexyl）pyrrolo pyrrole-1,4-dione（Bu PDPPPBu）, have been studied in this work. Well aligned crystals of the three molecules were grown from para-xylene by droplet-pinned crystallization method. FETs based on these aligned crystals exhibit a hole mobility up to0.19 cm^2 V 1s 1and electron mobility up to 0.008 cm^2 V 1s 1. The achieved hole mobility is of the same order of magnitude as reported highest hole mobility for DPP-based small molecules, but it is much lower than that of the high-performance DPP-based polymers. The relative low mobility is mainly attributed to the rough crystal surfaces with steps and, thus, non-smooth charge transport channels at the interfaces between the crystals and the dielectrics. This work has implications for understanding the low charge mobility of DPP-based small molecules.

Synthesis and characterization of novel red-emitting copolymers containing fluorene,diketopyrrolopyrrole,and phenothiazine units

A novel three-component copolymer (PFDP),derived from 9,9-dihexylfluorene,diketopyrrolopyrrole(DPP),and 10-octylphenothiazine,was synthesized through palladium-catalyzed Suzuki polycondensation in good yields. PFDP possessed moderate molecular weight and polydispersity,well-defined structure,and excellent thermal properties with an onset decomposition temperature at 357℃. PFDP in thin film exhibited red photoluminescence from DPP chromophore exclusively,with a peak at 602 nm. Electron-rich phenothiazine units sighificantly improved the injection and transport of holes by incorporating into polymer backbone. Light-emitting device was fabricated in the ITO/PEDOT:PSS/PVK/ polymer/Ba/Al configuration using PFDP as the emitting layer. The device based on PFDP showed red emission [CIE coordinate value (0.62,0.38)] that was close to the standard red (0.66,0.34). The results on electroluminescent performance revealed that PFDP may be a promising candidate for the red emitter with a maximum brightness of 259 cd/m2 and a maximum external quantum efficiency of 0.25%.

Diketopyrrolopyrrole-derived organic small molecular dyes for tumor phototheranostics

Cancer is one of the leading causes of human death around the world. Phototherapy, including photodynamic therapy(PDT) and photothermal therapy(PTT), is an emerging light-triggered cancer treatment and shows the advantages of non-invasiveness and low side effects. The design and preparation of efficient phototherapeutic agents are of great significance for phototherapy. Diketopyrrolopyrrole(DPP) is a small molecular organic dye featuring outstanding photophysical properties, facile tuning of structures and properties, and excellent photostability;thus, phototherapeutic agents based on organic small molecular DPP derivatives have attracted significant research attention for not only phototherapy but also photodiagnosis of fluorescence imaging(FLI) and photoacoustic imaging(PAI). This review summarizes the recent progress of various DPP-based organic small molecules on phototheranostics during the last five years. The molecular structure design and their phototheranostics performances are discussed in detail,as will be of great help for further creation of DPP-based phototheranostics.

Phthalimide and Naphthalimide end-Capped Diketopyrrolopyrrole for Organic Photovoltaic Applications

Two small molecules named PI-DPP and NI-DPP with a DPP core as the central strong acceptor unit and phthalimide/naphthalimide as the terminal weak acceptor were designed and synthesized. The effects of terminal phthalimide/naphthalimide units on the thermal behavior, optical and electrochemical properties, as well as the photovoltaic performance of these two materials were systematically studied. Cyclic voltammetry revealed that the lowest unoccupied molecular orbitals （LUMO） （- -3.6 eV） of both molecules were intermediate to common electron donor （P3HT） and acceptor （PCBM）. This indicated that PI-DPP and NI-DPP may uniquely serve as electron donor when blended with PCBM, and as electron acceptor when blended with P3HT, where sufficient driving forces between DPPs and PCBM, as well as between P3HT and DPPs should be created for exciton dissociation. Using as electron donor materials, PI-DPP and NI-DPP devices exhibited low power conversion efficiencies （PCEs） of 0.90% and 0.76% by blending with PCBM, respectively. And a preliminary evaluation of the potential of the NI-DPP as electron acceptor material was carried out using P3HT as a donor material, and P3HT：NI-DPP device showed a PCE of 0.6%, with an open circuit voltage （Voc） of 0.7 V, a short circuit current density （Jsc） of 1.91 mA·cm^-2, and a fill factor （FF） of 45%.

Small-molecule diketopyrrolopyrrole-based therapeutic nanoparticles for photoacoustic imaging-guided photothermal therapy

Therapeutic nanoparticles （NPs） based on the donor-acceptor-donor structured small organic molecule diketopyrrolopyrrole （SDPP） were prepared using a simple reprecipitation approach. These near-infrared radiation-absorbing NPs have high photothermal conversion efficiency and are able to selectively target cancer tissues through the enhanced permeability and retention effect. Benefiting from these advantages, SDPP NPs can serve as an excellent therapeutic agent for highly efficient and noninvasive photoacoustic imaging-guided photothermal therapy. Experiments using mouse tumor models showed that the SDPP NPs exhibited exceptional tumor ablation ability under laser irradiation （660 nm, 1.0 W.cm 2）, even at a low dose （0.16 mg.kg^-1）.

Synthesis of Conjugated Polymers Containing Diketopyrrolopyrrole(DPP)Building Block and the Photophysical Study

Sonogashira coupling of two different diketopyrrolopyrrole (DPP)-containing dihaloarenes with the same aromatic bisalkyne resulted in two new conjugated polymers with the same backbone but different pendant groups on the DPP moiety. The polymers were found to have designed chemical structures via structural characterizations in comparison with three monomers. The molecular weight measurement further demonstrated the formation of polymers with polydispersity index around 2, consistent with the polycondensation nature of the polymerization based on Sonogashira coupling. Both polymers could dissolve in many organic solvents, and the one with long alkyl side group on DPP moiety had better solubility. Photophysical investigation showed that both polymers had typical absorption/emission of conjugated polymers, and varying the solvent did not have large influence. Compared with other polar solvents, toluene reduced the quantum yield of fluorescence of the polymers, especially for the one with long alkyl pedant group, accompanying with slight red-shift in absorption/emission. The difference in the absorption/emission wavelengths between the polymers was similar to that between the corresponding monomers. Adding water into the THF solution of polymers reduced the emission intensity but no redshift was observed. Discussion about the structure-property relationships was carried out in detail.

Acceptor-Donor-Acceptor Conjugated Oligomers Based on Diketopyrrolopyrrole and Thienoacenes with Four, Five and Six Rings for Organic Thin-film Transistors

Three acceptor-donor-acceptor （A-D-A） conjugated oligomers, i.e., O1, 02 and 03, have been synthesized using diketopyrrolopyrrole （DPP） as an electron-acceptor unit, and naphtho[1,2-b：5,6-b＇]dithiophene （NDT）, anthra[1,2-b：5,6- b＇]dithiophene （ADT） or dithieno[3,2-b：Y,2＇-b＇]naphtbo[1,2-b：5,6-b＇]dithiophene （DTNDT） as electron-donor unit. These oligomers exhibit identical highest occupied molecular orbital （HOMO） and lowest unoccupied molecular orbital （LUMO） energy levels, which were ca. -5.1 and -3.3 eV, respectively. Upon thermal annealing, all three oligomers formed thin films with ordered microstructures, and their organic thin film transistors （OTFTs） exhibited p-type transport behavior. The mobility was increased with an extension of the size of D-units. 03 showed the best OTFT performance with the mobility of up to 0.20 cm2·V-1 ·s-1. The film quality of 03 was improved by adding 1 wt% poly（methylmethacrylate） （PMMA）. In consequence, the mobility of the O3-based devices was further enhanced to 0.30 cm2·V-1 ·s-1.

High-Efficiency Synthesis and Properties of Latent Pigment Red 272DPP-BOC by Microwave Irradiation

A high-efficiency synthesis method for a latent pigment of red pigment diketo-pyrrolo-pyrrole (Pig. Red 272:272DPP), which is important as a functional organic pigment, was investigated, and the investigation results revealed that irradiation of microwaves (MWs) for several seconds to 272 DPP in NMP (N-methyl-2-pyrrolidone) solvent yielded DPP latent pigment (272DPP-BOC) at a high yield of 86.2%. Two kinds of latent-pigment crystals, namely, red and yellow, were obtained by recrystallization, and it was found that the fluorescence-emission properties of the two kinds differ significantly. Single-crystal X-ray structural analysis showed that the difference in the fluorescence-emission properties of the two types is derived from the difference in their crystal structures.

A near-infrared porphyrin-based electron acceptor for non-fullerene organic solar cells

In this work, a new star-shaped electron acceptor based on porphyrin as core, rhodanine and benzothiadiazole as end groups, was developed for non-fullerene solar cells. The molecule shows three distinct absorption regions due to the Sorer and Q-bands of the porphyrin and the intramolecular charge transfer in the molecule. This molecule as electron acceptor was applied into non-fullerene solar cells by using a diketopyrrolopyrrole-based conjugated polymer as electron donor, An initial PCE of 1.9% was achieved with a broad photo-response from 300-850 nm. The results demonstrate that porphyrin can be used to design near-infrared electron acceptors for organic solar cells.

Fluoro-substituted DPP-bisthiophene conjugated polymer with azides in the side chains as ambipolar semiconductor and photoresist

Photoresists are essential for the fabrication of flexible electronics through all-photolithographic processes.Single component semiconducting photoresist exhibits both semiconducting and photo-patterning properties,and as a result,the device fabrication process can be simplified.However,the design of semiconducting polymeric photoresist with ambipolar semiconducting property remains challenging.In this paper,we report a single component semiconducting photoresist(PFDPPF4T-N_(3))by incorporating azide groups and noncovalent conformation locks into the side alkyl chains and conjugated backbones of a diketopyrrolopyrrole-based conjugated polymer,respectively.The results reveal that PFDPP4FT-N_(3) exhibits ambipolar semiconducting property with hole and electron mobilities up to 1.12 and 1.17 cm^(2) V^(−1) s^(−1),respectively.Moreover,field effect transistors with the individual photo-patterned thin films of PFDPP4FT-N_(3) also show ambipolar semiconducting behavior with hole and electron mobilities up to 0.66 and 0.80 cm^(2) V^(−1) s^(−1),respectively.These results offer a simple yet effective design strategy for high-performance single component semiconducting photoresists,which hold great potential for flexible electronics processed by all-photolithography.