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Surface functionalization with atoms serves as an important strategy to modulate the catalytic activities of low-dimensional nanomaterials. Herein, we developed a facile hydrogen incorporation strategy for improving the catalytic activities of SnS2 nanosheets toward CO2 electroreduction. Compared with SnS2 nanosheets, the hydrogen-incorporated SnS2 (denoted as H-SnS2) nanosheets exhibited high current density and Faradaic efficiency (FE) for formate. At -0.9 V vs RHE, H-SnS2 nanosheets displayed a maximum FE of 93% for carbonaceous product, which rivals the activities of most Sn-based catalysts in CO2 electroreduction. Mechanistic studies disclosed that the incorporation of surface hydrogen induced the electron injection into the structures of H-SnS2 nanosheets, which largely facilitates the process of CO2 activation. Density functional theory (DFT) calculations further revealed that hydrogen incorporation decreased the energy barrier for the formation of HCOO* intermediates, thus contributing to the CO2-to-formate conversion on H-SnS2 nanosheets.

The electron is unique and is regarded as the smallest reagent. In addition, electron transfer is universally involved not only in chemical systems but also in many other systems such as electrical conduction and life activity. In the field of synthetic organic chemistry, development of novel electron injection methods has led to a new phase of chemical bond formation techniques. In addition to conventional metallic reagents and electrolytic techniques, synthetically valuable reactions with noble metal-free electron initiators driven by thermal or photochemical stimulus have recently been developed intensively. In particular, visible-light organic photoredox catalysis has rapidly spread among synthetic chemists as a game-changing strategy because of its sustainability and versatility. This review focuses on modern state-of-the-art electron injection strategies for organic synthesis.

Solution-phase spectroelectrochemistry was used to study electron injection into colloidal CdSe quantum dots (QDs) with sizes ranging from 3.4 to 11.1 nm in tetrahydrofuran (THF). The absorbance an...

Recently, extracting hot electrons from plasmonic nanostructures and utilizing them to enhance the optical quantum yield of two-dimensional transition-metal dichalcogenides (TMDs) have been topics ...

Performance improved solution-processed blue phosphorescent organic light emitting diodes (PhOLEDs) are demonstrated by adopting a double electron transport layer (ETL) strategy, which consists of TPBi and an additional Alq3 ETL. With the help of Alq3 ETL, the performance of the optimal device with a double ETL is significantly enhanced. The maximum luminance of OLEDs is improved from 6787 cd m−2 to 13 054 cd m−2, and the maximum current efficiency is increased from 3.9 cd A−1 to 11.4 cd A−1. Furthermore, the difference of carrier injection in the two types of PhOLEDs is explored by using the transient electroluminescence measurement method. The results imply that double ETL can help to balance electron injection and carrier transport, reduce the interface charge accumulation, leading to a high efficiency. The PL decay of the emission layer with different ETL is detected to analyze the effect of the introduced second ETL layer and the interface on the exciton decay of the emission layer. The results show that the introduced interface in devices with a double ETL has an adverse effect on the exciton emission, which contributes to the serious efficiency roll-off of devices with a double ETL.

The performance of MoS2 based devices is closely related to the quality and defect morphology of the monolayer MoS2 deposited on metal. First-principles calculations were performed to investigate the vacancy effects of Au–mMoS2 contact. Four possible S-vacancy and a Mo-vacancy were considered in our calculations. Energetic studies show that S-vacancies are easier to form than Mo-vacancy in Au–mMoS2 contact, while S-vacancy (hollow site at interface, VS4) has the lowest formation energy under Mo-rich environments. Electron and charge redistribution analysis of defective Au–mMoS2 contact indicate that the lower contact resistance and higher electron injection efficiency of defective Au–MoS2 contact than perfect ones. Notably, the S-vacancy at top layer showed better electronic performance than that at bottom layer of monolayer MoS2 in the contact. High quality n-type Au–mMoS2 contact can therefore be expected through defect engineering.

Peripherally tetra-4-carboxyethylphenoxy substituted oxotitanium (IV), cobalt(II), zinc(II) and metal free phthalocyanines were synthesized to research the sensitizing abilities of these dye molecules in standard dye sensitized solar cells (DSSCs). All the synthesized phthalocyanine complexes have been characterized by using elemental analyses, UV-Vis, FT-IR, H-1 NMR and MALDI-TOF MS spectroscopic techniques. Electrochemistry of metallo phthalocyanines (MPcs) were studied with electrochemical and in-situ spectroelectrochemical measurements. H2Pc (7) and ZnPc (5) illustrated similar Pc based electron transfer reactions. Differently, CoPc (6) and TiOPc (4) illustrated metal based redox reactions, which enhanced the redox functionality of these complexes. Metal based reductions for CoPc (6) and TiOPc (4) were recorded in addition to the Pc based one. In-situ spectroelectrochemical measurements supported the proposed voltametric mechanism. Moreover, the color and spectra of the electrogenerated species were determined with the in-situ spectroelectrochemical analyses to predict possible optoelectrochemical application of the complexes. Pronounced optical and color changes during the electrolysis of the complexes indicated electrooptical and possible solid state electrochemical functionality of the complexes. TiO2 semiconductor on the fluoride doped indium tin oxide coated glass electrode (FTO) was decorated with H2Pc (7) and TiOPc (4) bearing four carboxyl anchoring groups and they were first of all tested as possible dye for the DSSC. H2Pc (7), TiOPc (4), CoPc (6) and ZnPc (5) dyes used in DSSCs showed 2.9%, 3.3%, 1.02% and 2.2% of power conversion efficiencies respectively.

The efficient cleavage of the N≡N bond is vital to N2 fixation but remains challenging. In this issue of Chem, Zhang and co-workers report that the interfacial polarization fields triggered by protrusion-shaped Fe single atoms on monolayer MoS2 can promote N≡N splitting via electron injection, resulting in a praiseworthy nitrogen electroreduction.

Using hot electrons to drive electrochemical reactions has drawn considerable interest in driving high-barrier reactions and enabling efficient solar to fuel conversion. However, the conversion efficiency from hot electrons to electrochemical products is typically low due to high hot electron scattering rates. Here, it is shown that the hydrogen evolution reaction (HER) in an acidic solution can be efficiently modulated by hot electrons injected into a thin gold film by an Au-Al

Engineered nanomaterials (ENMs) have been developed for imaging, drug delivery, diagnosis, and clinical therapeutic purposes because of their outstanding physicochemical characteristics. However, the function and ultimate efficiency of nanomedicines remain unsatisfactory for clinical application, mainly because of our insufficient understanding of nanomaterial/nanomedicine-biology (nano-bio) interactions. The nonequilibrated, complex, and heterogeneous nature of the biological milieu inevitably influences the dynamic bioidentity of nanoformulations at each site (i.e., the interfaces at different biological fluids (biofluids), environments, or biological structures) of nano-bio interactions. The continuous interplay between a nanomedicine and the biological molecules and structures in the biological environments can, for example, affect cellular uptake or completely alter the designed function of the nanomedicine. Accordingly, the weak and strong driving forces at the nano-bio interface may elicit structural reconformation, decrease bioactivity, and induce dysfunction of the nanomaterial and/or redox reactions with biological molecules, all of which may elicit unintended and unexpected biological outcomes. In contrast, these driving forces also can be manipulated to mitigate the toxicity of ENMs or improve the targeting abilities of ENMs. Therefore, a comprehensive understanding of the underlying mechanisms of nano-bio interactions is paramount for the intelligent design of safe and effective nanomedicines. In this Account, we summarize our recent progress in probing the nano-bio interaction of nanomedicines, focusing on the driving force and redox reaction at the nano-bio interface, which have been recognized as the main factors that regulate the functions and toxicities of nanomedicines. First, we provide insight into the driving force that shapes the boundary of different nano-bio interfaces (including proteins, cell membranes, and biofluids), for instance, hydrophobic, electrostatic, hydrogen bond, molecular recognition, metal-coordinate, and stereoselective interactions that influence the different nano-bio interactions at each contact site in the biological environment. The physicochemical properties of both the nanoparticle and the biomolecule are varied, causing structure recombination, dysfunction, and bioactivity loss of proteins; correspondingly, the surface properties, biological functions, intracellular uptake pathways, and fate of ENMs are also influenced. Second, with the help of these driving forces, four kinds of redox interactions with reactive oxygen species (ROS), antioxidant, sorbate, and the prosthetic group of oxidoreductases are utilized to regulate the intracellular redox equilibrium and construct synergetic nanomedicines for combating bacteria and cancers. Three kinds of electron-transfer mechanisms are involved in designing nanomedicines, including direct electron injection, sorbate-mediated, and irradiation-induced processes. Finally, we discuss the factors that influence the nano-bio interactions and propose corresponding strategies to manipulate the nano-bio interactions for advancing nanomedicine design. We expect our efforts in understanding the nano-bio interaction and the future development of this field will bring nanomedicine to human use more quickly.

Aggregation induced emission enhancement (AIEE) of newly synthesized (E)-2-(((2-(1-(2,3-dihydrobenzo[b] [1,4] dioxin-5-yl)-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)imino) methyl)naphthalen-1-ol (HBDPPIN) was analyzed in aqueous media. The AIEE active HBDPPIN in aggregated state exhibit turn-off emission with Cu2+ whereas HBDPPIN-Cu2+ complex reveal turn-on fluorescence with Al3+. The detection limit was calculated as 4.13 × 10–2 μM for Cu2+ and 9.4 × 10−1 μM for Al3+. The interfacial carrier transfer in the fabricated Cu-TiO2-HBDPPIN-Ag film depends on the interfacial contact of the layers: hole injection barrier of EAg-HBDPPIN > ETiO2-HBDPPIN, however, the electron injection barrier of ETiO2-HBDPPIN → C T HBDPPIN → C T TiO2 is the predominant charge transfer direction in Cu-TiO2-HBDPPIN-Ag film. The binding energy/energy gap (Eb /Eg) of HBDPPIN-CuO composites dependent on the nature of CuO cluster and carrier transfer in HBDPPIN-Cu6O6 composite is faster than other composites.

The operating lifetime of blue quantum-dot light-emitting diodes (QLED) is currently a short slab for this emerging display technology. To pinpoint the origin of device degradation, here we apply multiple techniques to monitor the electric-field distribution and space-charge accumulation across the multilayered structure before and after lifetime tests. Evident by charge-modulated electro-absorption and capacitance-voltage characteristics, the excited electrons in blue quantum dots (QD) are prone to cross the type II junction between the QD emission layer and the electron-transporting layer (ETL) due to the offset of conduction band minimum, leading to space-charge accumulation and operating-voltage rise in the ETL. Therefore, unlike those very stable red devices, of which the lifetime is primarily limited by the slow degradation of hole-transporting layer, the poor lifetime of blue QLED originates from the fast degradation at the QD-ETL junction. Materials engineering for efficient electron injection is prerequisite for the boost of operating lifetime., Wide application of quantum dot light emitting diodes (QLED) in display technology is hindered by the poor lifetime of the blue QLEDs. Here, the degradation mechanism is shown to originate from space charge accumulation in the electron-transporting layer enabling improvements in blue QLED lifetimes.

This study investigates low-temperature cross-linking of polyethyleneimine ethoxylated (PEIE) using four types of silane coupling agents, including trimethyl[3-(trimethoxysilyl)propyl]ammonium chloride (TTSPAC), trimethoxyphenylsilane (TMPS), trimethoxy[3-(phenylamino)propyl]silane (TPAPS) and 1,2-bis(trimethoxysilyl)ethane (BTMSE). The results of this study indicated that all the silane coupling agents reacted with PEIE at low temperatures ranging from 65 to 120 °C. The reacted PEIE exhibited solvent tolerance, indicating the cross-linking of PEIE. The cross-linked PEIE films were applied to electron injection layers (EILs) in solution-processed organic light-emitting devices. The device with PEIE: TTSPAC EIL showed a shorter device lifetime than that with only PEIE EIL. The shorter device lifetimes were attributed to the migration of chloride anions of TTSPAC. Conversely, the devices with PEIE: TMPS, TPAPS and BTMSE EILs, which did not contain mobile ions, had longer device lifetimes than that with only PEIE EIL. These results suggested that these improvements of device stability resulted from the cross-linking of PEIE.

The effect of a series of triarylamine based D-pi-A organic dyes, namely RK1, BA504, BA741 and the simple L1 reference dye on solid-state dye sensitized solar cells (s-DSSCs) performances was studied. The solid hole transporting material (HTM) was obtained by in-situ photoelectrochemical polymerization (in-situ PEP) process applied in two different media (water and acetonitrile) to produce the poly-3,4 ethylenedioxythiophene (PEDOT) conducting polymer (CP). A joint experimental and theoretical (density functional theory and time-dependent density functional theory) study is conducted to correlate the dye molecular structure containing different donor, pi-bridge or acceptor with several physicochemical characteristics such as optical (absorption and emission), electronic and redox properties of dyes in organic and aqueous medium; in-situ PEP process and charge transfer kinetics at the DSSC interfaces (Dye/TiO2 and Dye/HTM) through the alignment of the different energy levels of the dyes and electrodes. These properties are considered since they govern the performance of s-DSSCs denoted by the short-circuit current (J(sc)), open circuit cell potential (V-oc) and fill factor (FF). Among the four studied dyes, the s-DSSCs based on RK1, shows the best power conversion efficiency of 1.75% resulting from highest FF (0.57), V-oc (550 mV) and J(sc) (5.6 mA/cm(2)). The large differences in experimental photovoltaic performances of the obtained s-DSSCs have been well outlined and provide the guidelines for future development of more efficient solar-cell sensitizers.

The 8-hydroxyquinolinato lithium (Liq)|Ag system has been evaluated as the electron-injection layer for the MoOx| N,N′-di (1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB) charge-generation layer in tandem organic light-emitting diode (OLED) devices. From current-voltage studies of single-stack devices, it is determined that Liq is a relatively poor electron-transport material. However, Liq is found to be useful as an electron-injection layer with activation by Ag. Efficient tandem devices have been obtained using Liq|Ag as the electron-injection layer adjacent to the MoOx|NPB charge-generation layer, where the optimal Ag thickness is about 20–40 A and the activation of Liq can be seen with as little as 1 A of Ag.

Here, we use a simple and effective method to accomplish energy level alignment and thus electron injection barrier control in organic light emitting diodes (OLEDs) with a conventional architecture based on a green emissive copolymer. In particular, a series of functionalized zinc porphyrin compounds bearing π-delocalized triazine electron withdrawing spacers for efficient intramolecular electron transfer and different terminal groups such as glycine moieties in their peripheral substitutes are employed as thin interlayers at the emissive layer/Al (cathode) interface to realize efficient electron injection/transport. The effects of spatial (i.e., assembly) configuration, molecular dipole moment and type of peripheral group termination on the optical properties and energy level tuning are investigated by steady-state and time-resolved photoluminescence spectroscopy in F8BT/porphyrin films, by photovoltage measurements in OLED devices and by surface work function measurements in Al electrodes modified with the functionalized zinc porphyrins. The performance of OLEDs is significantly improved upon using the functionalized porphyrin interlayers with the recorded luminance of the devices to reach values 1 order of magnitude higher than that of the reference diode without any electron injection/transport interlayer.

In this work, a series of novel metal-free dyes were designed based on the C217 dye by changing the π-conjugated bridge, and then their electronic and optical properties were theoretically studied with density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. Moreover, the photovoltaic performances of designed dyes were quantitatively estimated by means of the (TiO2)38 cluster and bidentate bridging adsorption mode coupled with the incoherent charge hopping model. Results showed that bithiophene (BT) and biselenophene (BS), which redshift the strongest absorption peak about 19.7 nm and 42.7 nm, are superior to π-conjugated bridges than thieno[3,2-b]thiophene (TT). Furthermore, the photoelectric conversion efficiency (PCE) of C217 dye was predicted to be as high as 9.40%, which is in excellent agreement with the measured value (9.60% ∼9.80%). As expected, the cell sensitized by the designed dye 4 and 7 exhibited higher PCE of 11.50% and 12.69% than that sensitized by the C217 dye, an increase of 22.5% and 35.1%, denoting the dye 4 and 7 are more promising dye sensitizer candidates, and are worth further experimental studies. In addition, our results also revealed that it is essential to accurately estimate the electron injection rate and efficiency for designing and developing high- performable dye sensitizers.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) with layered structures provide a unique platform for exploring the effect of number of layers on their fundamental properties. However, the thickness scaling effect on the chemical properties of these materials remains unexplored. Here, we explored the chemically induced phase transition of 2D molybdenum disulfide (MoS2) from both experimental and theoretical aspects and observed that the critical electron injection concentration and the duration required for the phase transition of 2D MoS2 increased with decreasing number of layers. We further revealed that the observed dependence originated from the layer-dependent density of states of 2H-MoS2, which results in decreasing phase stability for 2H-MoS2 with increasing number of layers upon electron doping. Also, the much larger energy barrier for the phase transition of monolayer MoS2 induces the longer reaction time required for monolayer MoS2 as compared to multilayer MoS2. The layer-dependen...

Charge recombination at the ZnO photoanode/electrolyte interface is one of the major limitations for high performance dye-sensitized solar cells (DSSCs) toward their theoretical power conversion efficiency (PCE). Here, we proposed an efficient approach for reducing this interfacial losses and consequently facilitating charge transfer by decorating a hydrophobic thin-film on the surface of the dye-coated zinc oxide photoanode via 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) hexane solution immersing. As a result, a high PCE of 8.22% was obtained, which far exceeded the efficiency of 5.40% in a conventional DSSC without PFDTES treatment. Furthermore, PFDTES treatment also largely elongated the lifetime of photogenerated electrons, and maintained a good photo-response at the photoelectrode. This work provides a comprehensive explanation of electron injection, transfer and recombination at the ZnO photoanode/electrolyte interface, and a promising strategy to explore high efficiency ZnO-based DSSCs.

Efficient electron injection from cathode to electron transport layer is generally required to realize high-performance inverted organic light-emitting devices (IOLEDs). In this work, highly efficient IOLEDs are developed by employing a non-doped charge-generation unit of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/Al/LiF as electron-injection layers (EILs). The ultraviolet photoelectron spectroscopy (UPS) shows that the insertion of HAT-CN layer reduces the work function of EILs by 0.21 eV. Combined with the current-voltage characteristics of electron-only devices, the role of the HAT-CN layer in promoting electron injection is confirmed. What's more, the double EILs device with Rubrene as a probe verifies the strong hole blocking ability of HAT-CN/Al/LiF. Based on the EILs, the inverted blue phosphorescent OLEDs with a maximum current efficiency of 29.4 cd/A are realized. The excellent performance proves the superiority of HAT-CN/Al/LiF as EILs.

In this paper, we developed a novel electrochemiluminescence (ECL) sensing system based on polydopamine nanoparticles (PDA NPs) and MoS2 nanosheet aerogel. PDA NPs with phenylboronic acid (PBA) were synthesized as a novel kind of organic nano-luminophores. The PDA-PBA NPs had high ECL efficiency and regulable emitting wavelength (552 ~ 610 nm). MoS2 nanosheet aerogel played the important role in the improvement of ECL sensing performance. On the one hand, MoS2 nanosheet aerogel can load a large number of PDA-PBA NPs. The accommodation of PDA-PBA NPs in the MoS2 nanosheet aerogel kept the dispersed state, which prevented NPs aggregation and ECL quenching effect. On the other hand, the excellent conductivity of MoS2 nanosheet aerogel significantly facilitated the electron transfer. Electron injection with MoS2 nanosheet aerogel can effectively reduce the damage of PDA-PBA NPs by excessive hot electrons. As a result, the ECL signal of PDA-PBA NPs@MoS2 nanosheet aerogel have been amplified over 60 times than PDA NPs. Furthermore, the bright ECL light of PDA-PBA NPs@MoS2 nanosheet aerogel can be clearly observed with the smartphone. Finally, a target-catalyzed hairpin assembly (CHA) sensing mode was designed to visually detect MiRNA-126 (detection limit as 0.56 aM). The MoS2 nanosheet aerogel-based sensing system provided a new pathway in the development of ECL analysis research.

Organic chromophores can be synthesized by established methods and offer an opportunity to expand overall solar spectrum utilization for dye-sensitized photoelectrosynthesis cells. However, there are complications in the use of organic chromophores arising from the instability of their oxidized forms, the inability of their oxidized forms to activate a water oxidation catalyst, or the absence of a sufficiently reducing excited state for electron injection into appropriate semiconductors. Three new triarylamine donor–acceptor organic dyes have been investigated here for visible-light-driven water oxidation. They offer highly oxidizing potentials (>1 V vs NHE in aqueous solution) that are sufficient to drive a water oxidation catalyst and excited-state potentials (∼−1.2 V vs NHE) sufficient to inject into TiO2. The oxidized form of one of the chromophores is sufficiently stable to exhibit reversible electrochemistry in aqueous solution. The chromophores also have favorable photophysics. Visible-light-driven...

Interface engineering for the improved injection properties of all-solution-processed n-type organic field-effect transistors (OFETs) arising from the use of an inkjet-printed ZnO electron injection layer were demonstrated. The characteristics of ZnO in terms of electron injection and transport were investigated, and then we employed ZnO as the electron injection layer via inkjet-printing during the fabrication of all-solution-processed, n-type OFETs. With the inkjet-printed ZnO electron injection layer, the devices exhibited approximately five-fold increased mobility (0.0058 cm2/V s to 0.030 cm2/V s), more than two-fold increased charge concentration (2.76 × 1011 cm−2 to 6.86 × 1011 cm−2), and two orders of magnitude reduced device resistance (120 MΩ cm to 3 MΩ cm). Moreover, n-type polymer form smoother film with ZnO implying denser packing of polymer, which results in higher mobility.

Oxygen activation is a key reaction step in assorted thermal-catalytic processes. Here we use light pretreatment to boost oxygen activation by platinum, palladium, or gold loaded on TiO2. Light pretreatment improved catalyst performance by altering metal oxidation state and/or activated oxygen (Oads) generation. For Pt/TiO2 and Pd/TiO2, light pretreatment initially promoted Oads accumulation on the metal. In time, the metal deposits underwent oxidation with a concomitant decrease in the light pretreatment benefit. Au/TiO2 differed in that no Au oxidation was observed. Electrocatalytic assessment indicated that light pretreatment lowered the energy for oxygen activation and that Au was less able to activate oxygen overall. First-principles calculations demonstrated that light pretreatment reduces the oxygen dissociation barrier as each metal becomes negatively charged via electron injection from the TiO2 conduction bands. The calculations also illustrated the ability of Pt and Pd to stabilize the oxygen on...

TiO2-based dye-sensitization cycle is one of the basic strategies for the development of solar energy applications. Although the power conversion efficiency (PCE) of dye-sensitized devices has been improved through constant attempts, the intrinsically fatal factor that leads to the complete failure of the PCE of TiO2-mediated dye-sensitized devices has not yet been determined. Here, by using isotopically labeled MAS–1H NMR, ATR-FTIR spectroscopy (separate H/D and 48Ti/49Ti experiments), and ESR, we revealed that the accumulative formation of Ti–H species on the TiO2 surface is the intrinsic cause of the PCE failure of TiO2-based dye-sensitization devices. Such a Ti–H species is generated from the reduction of hydrogen ions (mostly released from dye carboxyl groups or organic electrolyte) accompanied by electron injection on the surface of TiO2, which deteriorates the PCE mainly by reducing the electrical conductivity of the TiO2 (by a maximum of ∼80%) and the hydrophilic nature of the TiO2 surface (contac...

In this work, a series of porphyrin-based sensitizers, coded as ZnTEP, ZnTTEP, and ZnTTTD in which different kinds of thienyl groups are used as the π-linker, have been designed and successfully synthesized. Their synthesis, photophysical and electrochemical properties, and theoretical DFT calculations, as well as their applications in dye-sensitized solar cells (DSSCs) are reported. The results showed that the power conversion efficiency (η) increases in the order of 1.14, 2.15 and 3.51% for ZnTEP, ZnTTEP and ZnTTTD, respectively. A significant improvement in the η value was achieved with ZnTTTD-based solar cells, which was approximately three times the magnitude when compared to the lowest ZnTEP-based solar cells. Moreover, the effects of chenodeoxycholic acid (CDCA) in a dye solution as a co-adsorbent on the photovoltaic performance of DSSCs were investigated. It was found that the coadsorption of CDCA can hinder the formation of dye aggregates and the improve electron injection yield and thus Jsc. The η value for ZnTTTD with the CDCA co-sensitizer dramatically increases up to 6.51%. This understanding of π-linker and co-sensitizer effects on the performance of porphyrins will serve as a guideline for the design of future dye sensitizers for DSSCs.

Two new Rh2(II,II) dyes were synthesized and anchored to TiO2 for charge injection upon irradiation. The 1ML-LCT (metal/ligand-to-ligand charge transfer) excited state is populated upon excitation, which decays to the corresponding 3ML-LCT state. Ultrafast electron injection into TiO2 from the Rh2(II,II) dyes was achieved with low energy, red light excitation.

A dye-sensitized solar cell was constructed on the basis of encapsulating the ruthenium polypyridyl photosensitizer Z907 in the macrocycle cucurbit[7]uril (CB7). The work focuses on the photophysical properties of the new host-guest complexes in acetonitrile and water (volume ratio 1:9) and on the top of nanocrystalline titanium dioxide (TiO2) electrode prior to the addition of poly(3-hexylthiophene) polymer and gold electrode. Complexation to CB7 in aqueous solutions has decreased the emission intensity and excited-state lifetime for metal-to-ligand charge transfer (MLCT) state at 650 nm by twofold because of collisional quenching, which opens a non-radiative deactivation channel. Similarly, a twofold decrease in the emission intensity and excited-state lifetime of MLCT at 750 nm on the top of TiO2 electrodes was observed with the addition of CB7. Encapsulation of Z907 dye to CB7 host has, also, led to fourfold enhancement in the short circuit current and power conversion efficiency of the final solar cell. The results support the premise that host-guest complexation of CB7 facilitates faster electron injection from Z907 dye into the conduction band of TiO2 electrodes.

Color-tuning for phosphorescent emitters in organic light-emitting diodes (OLEDs) across the entire visible spectrum is prerequisite to fulfil flexible full-color displays and white solid-state lighting. Heteroleptic 2-phenylpyridine-type (ppy-type) Ir(III) and Pt(II) complexes as phosphorescent emitters have been well exploited in the electroluminescence (EL) field due to their outstanding EL performance. Furthermore, the photophysical characters of these heteroleptic Ir(III) and Pt(II) complexes are generally dominated by the nature of cyclometalating ppy-type ligands. Accordingly, either sophisticated modification or judicious combination of different cyclometalating ppy-type ligands will provide a wonderful platform to tune their emission color. In this personal account, we put a special emphasis on our contributions to the novel color-tuning strategies in these heteroleptic ppy-type Ir(III) and Pt(II) complexes. In addition, afforded by our novel color-tuning strategies, ambipolar character or enhanced electron injection/transport (EI/ET) features can be furnished to bring high EL performances.

A series of metal-quinolate (MQ2) materials (M = Be2+, Mg2+, Ca2+, and Sr2+) were theoretically investigated to understand their electronic and charge transport properties as an application of electron injection layer (EIL) and additive material to electron transporting layer (ETL). It was found that the Be2+, Mg2+, and Ca2+ are tetragonally coordinated to the quinolate ligands whereas the Sr2+ is planarly coordinated. The analyses of electronic properties indicated that the stable lowest unoccupied molecular orbital (LUMO) energy level of these materials relative to LiQ is expected to improve the electron injection from cathode and enhance the electron transport in ETL. In perspective of electrochemical reactivity, the chemical hardness values of MQ2 materials showed that hole and electron carriers can be easily facilitated in order of BeQ2

We have prepared titania nanoparticles with an organic dye sensitiser and diarylethene molecular switch attached to the surface. Spectroscopic investigations show that the dye sensitiser's electron injection efficiency is reduced when the diarylethene is switched from its colourless, ring-open isomer to its coloured, ring-closed isomer, due to the introduction of a competing energy transfer pathway.

A new heteroleptic complex, [Ru(dcbH 2 )(bpy)(9AA)Cl] 2+ , Ru-9AA (9AA = 9-aminoacridine), was synthesized, characterized and used along with the previously synthesized [Ru(dcbH 2 )(bpy)(TCNE)Cl], Ru-TCNE (TCNE = tetracyanoethylene), in dye-sensitized solar cells (DSCs). The photoelectrochemical data were evaluated in comparison to the standard [Ru(dcbH 2 ) 2 (NCS) 2 ] dye, N3 . DSCs sensitized by these compounds exhibit overall efficiency conversion of 0.95 and 2.82% for Ru-9AA and Ru-TCNE , respectively, while that for N3 is 5.65% in the same condition. In spite of presenting lower global efficiencies than the standard dye, the Ru-TCNE complex present adequate electron injection efficiency and convert light into electricity effectively.

A beryllium complex, Be(FBTZ)2 (HFBTZ: 2-(benzo[d]thiazol-2-yl)-5-fluorophenol), has been synthesized with the aim of developing electron transport materials (ETMs) for phosphorescent organic light-emitting diodes (PhOLEDs). The complex exhibits a high triplet energy of 2.62 eV which is able to confine triplet excitons of green or lower-energy emissive phosphorescent emitters within the emitting layer. Moreover, it possesses a low-lying LUMO energy level (−3.14 eV) allowing efficient electron injection and a high election mobility of 1.8–1.1 × 10−4 cm2 V−1 s−1 for efficient electron transport. These characters enable Be(FBTZ)2 to act as an excellent ETM in PhOLEDs. By using the complex as an electron transport layer (ETL), structurally simple green, yellow and red PhOLEDs exhibiting extremely low turn-on voltages (Von) of 2.3, 2.1 and 2.2 V and high power efficiencies (PE) up to 65.0, 84.9 and 23.1 lm W−1, respectively, have been successfully fabricated. Be(FBTZ)2 can also work as a host material for PhOLEDs as demonstrated by a green device with a maximum PE of 42.8 lm W−1 and a Von value of 2.3 V.

Simple hydrochloric acid treatment of the corresponding pyridine precursors enable the resulting pyridine hydrochlorides to act as the solution-processed bifunctional electron injection/electron transporting materials. The all-solution-processed super yellow-based fluorescent OLEDs revealed excellent performance with an external quantum efficiency of up to 6.6% and extremely low efficiency roll-off over a wide range of luminance.

In this study, nine different natural dyes having various anchoring groups were extracted from various plants and used as photo-sensitizers in DSSC applications. The photovoltaic parameters controlling the cell performance were investigated and the results were discussed as a function of anchoring groups. The obtained power conversion efficiencies (PCEs) vary from 0.18 to 1.87%, while the quantum yields are heavily dependent on both the anchoring group and type of pigments. Moreover, the effects of anchoring groups on the photoinduced electron injection dynamics from natural dye molecules to TiO2 nanoparticles were studied using time resolved fluorescence spectroscopy measurements. In these dyes, the long-hydroxyl & carbonyl-chain bearing anthocyanin, with the maximum electron transfer rate (kET), has shown the best photosensitization effect with regard to cell output. Despite the fact that their performance in DSSCs is somewhat lower or close to the metal complexes, these metal-free natural dyes can be treated as a new generation of sensitizers.

The development of electron injection materials is one of the most important steps for obtaining highly efficient low-driving-voltage organic light-emitting devices (OLEDs). In this paper, we report poly(ionic liquid) (PIL)-based electron injection layers (EILs) for solution-processed OLEDs. We synthesized poly(N-alkyl-4-vinyl-pyridinium iodide) containing three different alkyl chains (propyl, butyl, and hexyl chains) and investigated the charge-transfer interactions between the pyridinium cations and the iodide anions along with the electronic structures and thermal properties of the PILs. We also fabricated and evaluated OLEDs containing PILs as EILs. The fabricated OLEDs exhibited lower driving voltages than the conventional device containing an alkali metal complex (8-quinolinolato lithium) as the EIL. The longer alkyl chain of the PILs was more effective in reducing the driving voltage.

In dye-sensitized solar cells (DSSCs), the HOMO–LUMO energy gap of organic sensitizers should be large enough to enable efficient electron injection and dye regeneration. However, the LUMOs of most practical organic dyes are always too high, making energy “waste”. In order to deepen the LUMOs, we focus on the targeted modulation of the molecular energy levels by embedding an electron donor or acceptor into the skeleton of a typical D–π–A model. The electron-rich group of 3,4-ethylenedioxythiophene (EDOT) lifts up the HOMO level with little influence on the LUMO, while the electron-deficient group of benzothiadiazole (BTD) or benzooxadiazole (BOD) mainly lowers the customized LUMO level. As a consequence, the auxiliary group change from EDOT (dye WS-53) to BOD (dye WS-55) brings forth a huge photoelectric conversion efficiency (PCE) increase by 38 fold from 0.24 to 9.46% based on an I−/I3− redox couple, and even reaching a high PCE of 10.14% with WS-55 under 0.3 sunlight irradiation.

Inverted quantum dot sensitized solar cells using non-toxic CuInSxSe2–x nanocrystals deposited on mesoporous NiO demonstrate high hole injection rates of 10–8 s–1 and record efficiencies of 1.25%.., Recent progress in quantum dot (QD) sensitized solar cells has demonstrated the possibility of low-cost and efficient photovoltaics. However, the standard device structure based on n-type materials often suffers from slow hole injection rate, which may lead to unbalanced charge transport. We have fabricated efficient p-type (inverted) QD sensitized cells, which combine the advantages of conventional QD cells with p-type dye sensitized configurations. Moreover, p-type QD sensitized cells can be used in highly promising tandem configurations with n-type ones. QDs without toxic Cd and Pb elements and with improved absorption and stability were successfully deposited onto mesoporous NiO electrode showing good coverage and penetration according to morphological analysis. Detailed photophysical charge transfer studies showed that high hole injection rates (108 s–1) observed in such systems are comparable with electron injection in conventional n-type QD assemblies. Inverted solar cells fabricated with various QDs demonstrate excellent power conversion efficiencies of up to 1.25%, which is 4 times higher than the best values for previous inverted QD sensitized cells. Attempts to passivate the surface of the QDs show that traditional methods of reduction of recombination in the QD sensitized cells are not applicable to the inverted architectures.

By using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, the electronic structures and optical properties of a single dye (C239, C259 and C259-N) and co-sensitized dyes (C239+C259 and C239+C259-N) were studied. It is found that the effect of the replacement of dithienopyrrole (DTP) with cyclopentadithiophene (CPDT) in C259 on dye performance is negligible. There is no valley in the light-harvesting efficiency curve for the co-sensitized dyes, and the molar absorbtivity of the co-sensitized dyes at the maximum absorption has been improved compared with a single dye. Further investigations on the co-sensitized dye/TiO 2 complexes show that the A co-sensitization mode with the formation of three O–Ti bonds and a new hydrogen bond is more stable. The co-sensitized dye with the benzoic acid group can stay perpendicular on the titanium surface, this is favourable for electron injection and can weaker electron-hole recombination at dye/TiO 2 interface. Our results can supply a guideline for experimental design of more efficient co-sensitized organic dyes for dye-sensitized solar cells (DSSCs).

Two hydroxamic acid anchoring based dyes, PTZ-HA and BTPA-HA were designed, synthesized and their DSSC performances were compared with that of the corresponding cyanoacetic acid anchoring group dyes (PTZ-CA and BTPA-CA) for better understanding of their enhanced DSSC performance. The hydroxamic anchored dyes, PTZ-HA and BTPA-HA have shown enhanced efficiency of 4.06 and 6.22 % when compared to cyanaoacetic acid dyes, PTZ-CA and BTPA-CA showing 2.99 and 5.65 % efficiencies, respectively. This particular enhancement in the efficiencies could be attributed to the stable bidentate keto anchoring mode of the hydroxamic acid group, which led to the efficient electron injection. The detailed optical, electrochemical and photovoltaic properties were analyzed and complimented with the density functional theory (DFT) studies.

Solution-processable charge injection materials have gathered considerable attention in the field of organic optoelectronics owing to their ability to enhance device efficiency. Of those candidates, polyethylenimine (PEI) polymers have been widely explored, but their effect on the device physics in organic light-emitting diodes (OLEDs) are not completely elucidated yet. In this work, the impact of ZnO:PEI hybrid nanocomposite as an electron injection layer (EIL) of OLEDs on the device performance is investigated. Two different PEIs with the different spatial molecular configuration of the polymer, either linear or branched-type, are employed. Both PEI polymers have the ability to effectively reduce the work-function of ZnO. The ZnO:linear-PEI EIL shows higher device efficiency in comparison to the ZnO:branched-PEI EIL in the charge-balanced OLEDs, whereas the results are opposite in the charge-imbalanced device setup. This is mainly due to the different role required of EIL materials upon different device working mechanisms. This work shows a series of experimental results of the detailed device characteristics using ZnO:PEI hybrid EILs in order to provide a systematic understanding of the device physics by combining two key concepts together; (1) control of the molecular configuration, and (2) charge carrier dynamics.

By adopting an 4,7-diphenyl-1,10-phenanthroline (Bphen):Ag interlayer with the gradient structure between the cathode and electron injection layer, the electron injection of white inverted top-emitting organic light-emitting devices (WITOLED) was enhanced. The structure of Ag–Ge–Ag anode capping with light outcoupling was used to ensure the spectral stability with the angles. The structure of the emission layer was carefully designed to guarantee the spectral stability with the voltages. The highest current efficiency of the WITOLED can reach 21.7 cd/A. The CIE 1931 coordinates varies only 0.022 in X and 0.015 in Y (0o–60o).

In this paper, we present the design of five new derivatives of triphenylamine dyes with variable thiophene rings (0–5) and shed light on their electrooptical and charge-injection properties. Computational techniques are used to study the effect of the thiophene moieties on the properties of interest, i.e., how the number of thiophene rings in π-conjugated systems influence the absorption spectra and electron injection of the dyes. The results show that the absorption spectra gradually became broad and red-shifted (384–542 nm) with the number of thiophene units. The effect of thiophene units on the performance of sensitizers in dye-sensitized solar cells is also determined. During theoretical examination, the electron injection efficiency (Φinject) and light harvesting efficiency (LHE) are determined. Results indicate that the selection of appropriate lengths of conjugated bridges in the dye sensitizer is very important in designing high-efficiency dyes.

Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs2CO3 in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m2, the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m2 which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given ...

We report the effect of gap states on energy level alignment in a typical organic charge generation interface of N,N-bis(1-naphthyl)-N,N-diphenyl-1,1-biphenyl-4,4-diamine (α-NPD)/hexaazatriphenylene−hexacarbonitrile [HAT(CN) 6 ] by using ultraviolet and X-ray photoemission spectroscopy. The gap states tailed from the highest occupied molecular orbital (HOMO) onset of α-NPD dominate the Fermi level pinning at the α-NPD( 6 interface, which is favorable for charges generation upon bias operation and facilitates the electron injection from the HOMO-tail region of α-NPD to the lowest unoccupied molecular orbital (LUMO) region of HAT(CN) 6 .

We report new electron injection lithium complexes, lithium 2-(2-pyridyl)-3-pyridinolate (LIPPy) and lithium 4-phenyl-2-(2-pyridyl)phenolate (LIPPP) for low driving voltage and better stability of organic light emitting diodes (OLEDs). These materials were designed with the help of molecular simulation of anion formation energy and lithium binding energy calculations. Small anion formation energy and low binding energy of lithium complexes show good correlation with expected experimental driving voltage of the OLEDs. Fabricated OLEDs with these new lithium complexes exhibit lower driving voltage, higher power efficiency and longer lifetime as compare to the widely used and commercially available lithium 8-quinolate (Liq) and lithium 2-(2-pyridyl)phenolate (LIPP).