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Redox mediators play a major role in determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Copper complexes are a good option for redox mediators but suffer from elec...

Oligo-meta-phenylenes have been designed and synthesized as multipotent base materials of single-layer organic light-emitting devices. Simple molecular structures of oligo-meta-phenylenes composed of linear phenylene arrays benefited from the wealth of modern reactions available for biaryl couplings and were concisely synthesized in a series. Structure-performance relationship studies with the first seven congeners revealed key features important for the multipotent materials in single-layer devices. As a result, highly efficient phosphorescent electroluminescence was made possible in a highly simplified device architecture comprising one-region, single-layer configurations. Detailed investigations with hole-only devices disclosed that the hole mobility was effectively retarded by potent materials, which should facilitate hole/electron recombination for electroluminescence.

Various types of organic dyes were synthesized to enhance efficiency over past years. Understanding structure-property relationships is a significant issue to develop novel dye for high efficiency dye-sensitized solar cells (DSSCs). In this work, three novel dyes (JY40-1–JY42-1) with ullazine as donor were designed based on the dye sensitizers JY40, JY41 and JY42, and their geometrical structures, absorption spectra as well as optical properties were theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). Compared with original dyes, JY40-1–JY42-1 will exhibit better J SC due to higher light harvesting efficiency (LHE), regeneration driving force ( Δ G inject ), stronger and broader absorption spectra, superior ICT properties, and lower the driving force of regeneration ( Δ G reg ) as well as reorganization energy ( λ total ). According to the analysis of interfacial interaction between the dye and electrolyte, JY40-1–JY42-1 have lower electron recombination rate, which further increase V OC . Hence, ullazine group as electron donor can effectively enhance efficiency of DSSCs according to the above analysis. In addition, JY42 exhibits a better balance in various important properties among three original dyes, which is in good agreement with the experimental results. This work provide a guidance for molecular engineering and screen high-efficiency sensitizers for DSSCs.

Hierarchical flower-like TiO2 microspheres (FMS) and TiO2 nanorice (NR) were obtained, respectively, by controlling the dosage of Ti precursor via a simple hydrothermal process. Flower-like TiO2 microspheres consist of nanopetals grown from the center radially, the nanopetals are about several nm in average thickness, and each nanopetal has a thinned tip with an average size of 15 nm. The unique hierarchical TiO2 microspheres with large surface area (118.6 m2 g−1) suggested its potential application in dye-sensitized solar cells (DSSCs). The power conversion efficiency of FMS-based DSSCs (9.58%) is much higher than that of NR-based DSSCs (7.13%), which could be ascribed to its excellent light-scattering and dye absorption ability, shorter electron transport pathway and longer electron recombination time derived from the thin thickness and large specific surface area of nanopetals.

A way of exciting nuclei using reverse conversion is studied. Nuclear excitation occurs due to resonance absorption of the kinetic energy of the recombining electron and its binding energy in the final state. Calculations of triggering cross sections are made using reverse conversion of the energy of ions of isomeric nucleus 129mSb on a bare nucleus and lithium-like ions. Experiments to study this process are performed in the storage rings of the GSI in Darmstadt and the IMP in Lanzhou.

Metal chalcogenide complex (MCC) has been reported as a promising exchanger to link quantum dots onto photoanodes in quantum dot sensitized solar cells, which provides better chemical connectivity and electronic conductivity. However, the reported efficiencies are far lower than average efficiencies for quantum dot sensitized solar cells using traditional exchangers, which is majorly ascribed to the low short current densities. Serious electron recombination among MCC connected quantum dots are proposed and proved according to transient photoluminescent spectra, which reduces short current densities.

Time dependent density functional theory calculations are applied on a series of molecular photocatalysts of the type [(tbbpy)2M1(tpphz)M2X2]2+ (M1 = Ru, Os; M2 = Pd, Pt; X = Cl, I) in order to provide information concerning the photochemistry occurring upon excitation of the compounds in the visible region. To this aim, the energies, oscillator strengths and orbital characters of the singlet and triplet excited states are investigated. The structural modifications of the complexes have a strong impact on the excited states properties. In particular, it is found that the main differences concern the energies of the charge-separated and metal-centered states. The analysis of these differences provides general trends for the efficiency of population transfers between the states, particularly regarding the charge separation and electron recombination processes.

Temperature-dependent spectral response mechanism in GaAs-based blocked-impurity-band (BIB) far-infrared detectors has been investigated. Device structure, processing steps and physical models are described in detail. In this work, our discussion is mainly focused on the operation temperature (Tope) of BIB detector. It is demonstrated that the critical Tope and the optimal Tope both exist for GaAs-based BIB detector. It is only when the temperature-assisted photo electron excitation process is fundamentally equivalent to the temperature-assisted photo electron recombination process that the optimal Tope occurs, and it is only when the temperature-assisted photo electron excitation process is dominated by the temperature-assisted photo electron recombination process that the critical Tope occurs.

Uniform $TiO_2$ blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating $TiO_2$ BLs of 0, ...

The recombination rates of two typical D–π–A dyes have been evaluated qualitatively by means of quantum chemical calculations. By dissecting the geometrical and electronic structures of the dyes, the function of the inserted phenyl ring in inhibiting recombination is recognized as the blocking of back electron transfer and decreasing the HOMO distribution on the anchoring group, but with the distorted structure caused by the inserted benzene ring also decreasing the light harvesting ability. Molecular designs for the screening of potential dyes are carried out with a comprehensive consideration of both suppressing recombination and enhancing light absorption. Tightening the adjacent rings in the donor and π-spacer is verified to be a feasible route for extending the π-conjugation, thus leading to red-shifted and broad absorption spectra. The calculated results show that the dyes possessing both a small distribution of the HOMO on the anchoring group and a relatively strong light harvesting ability are the most promising candidates for use in dye-sensitized solar cells. Moreover, this work provides a deep understanding of the relationship between the electron recombination rate and electronic structure of dyes, and provides theoretical guidelines for the design of high performance sensitizer materials.

Sandwich-type polyoxometalates K6Na2Ni2[Ni4(H2O)2(SiW9O34)2]·30H2O(Ni4), K6Na2Co2[Co4(H2O)2(SiW9O34)2]·30H2O(Co4) and K10[Ni(H2O)2(γ-SiW10O35)2]·13.25H2O(Ni1) were doped into TiO2 separately and applied as photoanodes for dye-sensitized solar cells (DSSCs) for the first time, enhancing the current intensity and photoelectric conversion efficiency of the cells. The TiO2 and POM@TiO2 used in this paper were synthesized by a modified sol–gel method. The Jsc of pure P25 is 15.84 mA cm−2, the Voc is 0.637 V, the FF is 0.564, and the η is 5.69%. The Jsc of the prepared TiO2 is 16.48 mA cm−2, the Voc is 0.68 V, the FF is 0.537 and the η is 6.01%, which is a higher efficiency than that of pure P25, therefore the POMs@TiO2 were directly used in photoanodes without being formed into composites with P25 in this paper. The Jsc of 0.8% Ni4@TiO2 is 18.79 mA cm−2, the Voc is 0.71 V, the FF is 0.595 and the η is 7.94%, which is 32.1% higher than that of the prepared TiO2 based DSSC. 0.8% Co4@TiO2 and 0.8% Ni1@TiO2 modified photoanodes obtained power conversion efficiencies of 6.22% and 6.17%. The electron lifetimes of the self-prepared TiO2 and 0.8% Ni4@TiO2 are 13.5 ms and 28 ms respectively, calculated from a bode plot. Among the three kinds of sandwich-type POMs mentioned in this paper, the 0.8% Ni4 modified photoanode in DSSCs exhibited the best performance in enhancing light harvesting and reducing electron recombination. The energy levels of Ni4 were also investigated.

Highlights The TTC layer was efficiently deposited at the grain boundary of the perovskite, which passivated the grain surface and grain boundary, thereby decreasing the interfacial recombination of the perovskite solar cells.The hydrophobic small molecule TTC on the perovskite films forms a water-resistant layer that protects the perovskite from water damage. Electronic supplementary material The online version of this article (10.1007/s40820-019-0282-0) contains supplementary material, which is available to authorized users., The advancement of perovskite solar cells (PVSCs) technology toward commercialized promotion needs high efficiency and optimum stability. By introducing a small molecular material such as tetratetracontane (TTC, CH3(CH2)42CH3) at the fullerene (C60)/perovskite interface of planar p-i-n PVSCs, we significantly reduced the interfacial traps, thereby suppressing electron recombination and facilitating electron extraction. Consequently, an improved efficiency of 20.05% was achieved with a high fill factor of 79.4%, which is one of the best performances for small molecular-modified PVSCs. Moreover, the hydrophobic TTC successfully protects the perovskite film from water damage. As a result, we realized a better long-term stability that maintains 87% of the initial efficiency after continuous exposure for 200 h in air. Electronic supplementary material The online version of this article (10.1007/s40820-019-0282-0) contains supplementary material, which is available to authorized users.

This chapter presents a thorough review on the role of tin oxide (SnO2) as a photoanode, either as pure or composite, with another material in dye-sensitized solar cells (DSSCs). The research in SnO2-based DSSCs is fueled by its electron mobility, which is several orders of magnitude higher than the most successful photoanode (TiO2), so much so that the transport-driven electron recombination could be minimized. The SnO2 has been developed in diverse morphologies with differing surface and electronic properties, and, therefore, with varying photovoltaic properties. This chapter gives a thorough account on the SnO2-based DSSCs.

In this study, ultrasmall and ultrafine TiO 2 quantum dots (QDs) were prepared and used as a high-performance compact layer (CL) in dye-sensitized solar cells (DSCs). We systematically investigated the performance of TiO 2 CL under both low-intensity light and indoor fluorescent light illumination and found that the efficiency of DSCs with the insertion of optimal TiO 2 QDs-CL was increased up to 18.3% under indoor T5 fluorescent light illumination (7000 lux). We clarified the controversy over the blocking effect of TiO 2 CL for the efficiency increment and confirmed that the TiO 2 QDs-CL performed significantly better under low-intensity illumination due to the efficient suppression of electron recombination at the FTO/electrolyte interface. We, for the first time, demonstrate this potential for the application of the DSCs with TiO 2 QDs-CL in the low-intensity light and indoor fluorescent light illumination.

Dye-sensitized solar cells (DSSCs) represent a promising technology in the renewable energy portfolio. In this study, tin-doped-indium oxide (ITO) nanowires are used to prepare DSSC photoanodes that overcome charge transport limitations associated with conventional nanoparticle-based photoanodes. Vertically-aligned ITO nanowires are grown by a thermal evaporation method and a porous TiO 2 shell layer is uniformly coated on the nanowire surfaces to ensure high dye-loading. It is found that cell efficiency increased to 4.85% from 2.81% when a dense HfO 2 blocking layer is inserted between ITO nanowire surfaces and the porous TiO 2 shell. While more photoactive surface area associated with longer nanowires improves device performance, nanowires longer than 20 μm show reduced efficiency from an increase in electron recombination. Therefore, 20-μm-long nanowires show the best efficiency, which is attributed to the balance of surface area and electron recombination in the photoanode. Although decreasing TiO 2 annealing temperatures from 600 to 400 °C increases electron recombination, the smaller TiO 2 nanoparticles at 400 °C lead to much higher dye-loading and, ultimately, the highest device efficiency of 5.59%.

The performance of dye-sensitized solar cells (DSSCs) can be influenced by the sensitizer. Therefore, three heteroleptic ruthenium complexes, cis-[Ru(dcbpy)(bpy)(NCS)2] (Ru-bpy), cis-[Ru(dcbpy)(dppz)(NCS)2] (Ru-dppz) and cis-[Ru(dcbpy)(dppx)(NCS)2] (Ru-dppx) (dcbpy = 4,4′-dicarboxylic-2,2′-bipyridine, NCS = isothiocyanate) sensitizers, were synthesized using one pot synthesis. The structures and functionalization of the ligands in each complex sensitizer were confirmed using FT-IR and NMR analyses. They were then systematically studied to determine their light absorption spectrum, the metal-centered oxidation peak, and electron recombination properties using a UV–vis spectrophotometer and electroanalytical techniques (i.e., CV, EIS, and LSV). The criteria for an efficient DSSC ruthenium sensitizer were drawn based on the structure-property relationship. It was found that the power conversion efficiency (ɳ) of the sensitizers were in the sequence of Ru-dppz (ɳ = 0.40%)

A non-elemental luminescence band with a maximum at 630 nm was studied in the undoped ZnSe crystals. This broad luminescence band was expanded into components by the Alentsev-Fock method, and the two basic elemental components were identified at room temperature. For these elemental components, mechanisms of recombination were established by comparing the temperature dependences of the luminescence intensity at different wavelengths. These components were named: D+–band (hvmax= 1.875 eV, 661 nm, δ = 0.181 eV) with the hole recombination mechanism and D––band (hvmax= 2.028 eV, 611 nm, δ = 0.196 eV) with the electron recombination mechanism.

The complete dye-sensitized solar cell (DSC) life cycle includes three stages: “mature” period, stability period and degradation period. However, during the DSC performance adjustment period, considering the influence of both sides of the dyed-TiO2/electrolyte interface on the electron recombination process is still blank. In this paper, the effects of the environment on both sides of the interface between TiO2 and electrolyte during the DSC performance adjustment on the electron recombination process are studied. The results show that the performance adjustment of DSC is greatly influenced by the chemical environment of electrolyte. The film microstructures have a certain influence on the electron recombination process during the performance adjustment. During the performance adjustment period of DSC, the adjustment of quasi-Fermi level is more complicated under the condition of weak light than under the condition of strong light. The results of this paper are significant for studying complex systems of DSC, understanding the device working mechanism and improving the cell efficiency.

A nanocomposite porous electrode structure consisting of hierarchical iodine-doped zinc oxide (I-ZnO) aggregates combined with the two simple solution-processed interfacial modifications i.e. a ZnO compact layer (CL) and a TiO 2 protective layer (PL) has been developed in order to understand electron transport and recombination in the photoanode matrix, together with boosting the conversion efficiency of I-ZnO based dye-sensitized solar cells (DSCs). Electrochemical impedance spectra demonstrate that ZnO CL pre-treatment and TiO 2 PL post-treatment synergistically reduce charge-transfer resistance and suppress electron recombination. Furthermore, the electron lifetime in two combined modifications of I-ZnO + CL + PL photoelectrode is the longest in comparison with the other three photoelectrodes. As a consequence, the overall conversion efficiency of I-ZnO + CL + PL DSC is significantly enhanced to 6.79%, with a 36% enhancement compared with unmodified I-ZnO DSC. Moreover, the stability of I-ZnO + CL + PL cell is improved as compared to I-ZnO one. The mechanism of electron transfer and recombination upon the introduction of ZnO CL and TiO 2 PL is also proposed in this work.

Dithiafulvenyl–triphenylamine (DTF–TPA) based organic dyes with different alkyl chains attached on the DTF unit were examined to investigate the effect of alkyl chain lengths on the photovoltaic performances of dye-sensitized solar cells (DSSCs). Relative to WD9 with two methyl groups, the power conversion efficiency (η) increased significantly from 3.18% to 4.29% (WD12 with two hexyl chains) and 4.62% (WD13 with two decyl chains) in the absence of the chenodeoxycholic acid (CDCA). An increase in η of about 45.2% was obtained from WD9 to WD13. The attached longer alkyl chains in DTF–TPA based organic dyes are effective to suppress the electron recombination and reduce the interactions between dye molecules. Electrochemical impedance spectroscopy studies indicate that both the resistance for charge recombination and the electron lifetime are increased after the increase of alkyl chains length to the dye molecules. The η of DSSC based on WD9 was markedly increased by about 28.6% in the presence of CDCA as compared to that in the absence of CDCA. However, the η of WD13-sensitized DSSC was not dependent on CDCA and decreased by about 5.4% in the presence of CDCA. This work indicates that the incorporation of longer alkyl chains into DTF–TPA organic dyes is a promising way for efficient coadsorbent-free DSSCs.

An ultrathin SiO2 under-layer was inserted between the FTO substrate and the Ti-doped hematite film to suppress the reverse electron recombination from the FTO substrate to the hematite layer for improved photoelectrochemical activity of the hematite film during the photoelectrochemical (PEC) water splitting reaction. The reverse current of the SiO2 under-layered hematite thin film decreased from −0.075 mA cm−2 to −0.035 mA cm−2, with enhanced interfacial charge transfer and internal charge transport efficiencies. The hematite film with the ultrathin SiO2 under-layer showed a promising photocurrent density of 0.76 mA cm−2 at 1.23 V vs. RHE under 1 sun illumination without hole scavenger materials during the PEC water splitting reaction.

In this work, we report for the first time the improvement of the photovoltaic characteristics of DSSCs by mixing TiO2 with WO3. WO3 reduced the surface trap states of TiO2, which suppressed the charge recombination and increased the driving force of electron injection, thereby improving its power conversion efficiency. It was observed that DSSCs fabricated using the WO3-mixed TiO2 films show the maximum conversion efficiency of 4.84% because of the effective prevention of the electron recombination. DSSCs based on WO3-mixed TiO2 films showed better photovoltaic performance than cells fabricated with only TiO2 nanoparticles.

An InGaN light-emitting diodes with a leakage electron recombination (LER) quantum well have been proposed and investigated numerically by using the APSYS simulation software. The simulation results indicate that the AlGaN electron blocking layer inserted between the last two quantum wells changed the carrier concentrations distribution, and the leakage electrons can be further recombined with holes in the LER quantum well which can decrease the electrons that spill out from active region. As a result, the internal quantum efficiency and light output power are markedly improved attributed to LER quantum well.

New organic dyes containing fluorene functionalized with two imidazole chromophores as donors and cyanoacrylic acid acceptors have been synthesized and successfully demonstrated as sensitizers in nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs). The monoimidazole analogues were also synthesized for comparison. The Sommelet reaction of bromomethylated 2-bromo-9,9-diethyl-9H-fluorene produced the key precursor 7-bromo-9,9-diethyl-9H-fluorene-2,4-dicarbaldehyde required for the preparation of imidazole-functionalized fluorenes. Since the dyes possess weak donor segment, the electron-richness of the conjugation pathway dictated the optical, electrochemical, and photovoltaic properties of the dyes. The dyes served as sensitizers in DSSC and exhibited moderate efficiency up to 3.44%. The additional imidazole present on the fluorene has been found to retard the electron recombination due to the bulkier hydrophobic environment and led to high open-circuit voltage in the devices.

To supplement our study on thiocyanate-free ruthenium sensitizers (TFRS) for dye-sensitized solar cells (DSSCs), which belong to a class of Ru(II)-based complexes coordinated by a single 4,4'-dicarboxylic acid-2,2'-bipyridine and two symmetrically arranged functionalized trans-azolate chelates, we carefully isolated and characterized the second and less-abundant stereoisomer, in which the two pyridyl azolate ancillaries are asymetrically cis-arranged to each other. Two distinctive ancillaries, namely: 5-[4-(5-hexyl-2-thienyl)-2-pyridinyl]-3-trifluoromethyl pyrazole and 5-(6-tert-butyl-1-isoquinolinyl)-3-trifluoromethyl pyrazole, were employed in this study, giving a total of four sensitizers, that is, thienyl substituted TFRS-2 a and 2 b, and isoquinolinyl substituted TFRS-52 a and 52 b, in which the suffix b indicates the cis-stereoisomers. To gain insight into their fundamental properties their photophysical, electrochemical, and spectroelectrochemical behavior was investigated by density functional theory. Upon comparison of the correspondingly fabricated DSSCs, the sensitizers TFRS-2 a and 52 a yielded significantly higher conversion efficiencies than their asymmetrical cis-counterparts, TFRS-2 b and 52 b. To rationalize the cell performances charge extraction/photovoltage decay and impedance spectroscopic measurements were carried out to compare the rates of interfacial electron recombination from the TiO2 conduction band to the electrolyte.

Organolead halide perovskite solar cells (PSCs) show great promise as a new large-scale and cost-competitive photovoltaic technology. Power conversion efficiencies over 15% to 19% have been achieved within 18 to 24 months of development, and thus perovskite materials have attracted great attention in photovoltaic research. However, the manufacture of PSCs raises environmental concerns regarding the over-production of raw lead ore, which has harmful health and ecological effects. Herein, we report an environmentally responsible process to fabricate efficient PSCs by reusing car batteries to simultaneously avoid the disposal of toxic battery materials and provide alternative, readily available lead sources for PSCs. Perovskite films, assembled using materials sourced from either recycled battery materials or high-purity commercial reagents, show the same material characteristics (i.e., crystallinity, morphology, optical absorption, and photoluminescence properties) and identical photovoltaic performance (i.e., photovoltaic parameters and resistances of electron recombination), indicating the practical feasibility of recycling car batteries for lead-based PSCs.

This study investigates the optimization of a ZnO-coated TiO2 working electrode and the effect of this hybrid electrode on the power conversion efficiency of a dye-sensitized solar cell (DSSC). This electrode was fabricated by dipping the TiO2 electrode with the TiCl4 treatment in a solution of zinc acetate dehydrate [Zn (CH3COO)22H2 and ethanol. The effect of the concentration of Zn (CH3COO)22H2O on the band gap of a working electrode and on the power conversion efficiency of a DSSC was also examined. As the concentration of ZnO decreased to 0.002 from 0.004 mol/L, the band gap of the working electrode decreased to 3.08 eV from 3.87 eV, and the power conversion efficiency () of the DSSC increased to 3.8573% from 3.3514%. Interestingly, the of DSSC with a ZnO-coated TiO2 hybrid electrode substantially exceeded that of the conventional DSSC due to TiO2 orbital hybridization and an energy barrier between ZnO and TiO2 that suppressed the electron recombination.

Four new pyrrole-based organic sensitizers with different isolation groups were conveniently synthesized and applied to dye sensitized solar cells (DSCs). The introduction of isolation group in the side chain could both suppress the formation of dye aggregates and electron recombination. Especially, when two pieces of D-π-A chromophore moieties shared one isolation group to construct the "H" type dye, the performance was further improved. Consequently, in the corresponding solar cell of LI-57, a short-circuit photocurrent density (Jsc) was tested to be 13.85 mA cm(-2), while 0.72 V for the open-circuit photovoltage (Voc), 0.64 for the fill factor (FF), and 6.43% for the overall conversion efficiency (η), exceeding its analogue LI-55 (5.94%) with the same isolation group. The results demonstrated that both the size (bulk and shape) and the linkage mode between the D-π-A chromophores and the isolation groups, could affect the performance of sensitizers in DSCs in a large degree, providing a new approach to optimize the chemical structure of dyes to achieve high conversion efficiencies.

Electron recombination is one of the major loss factors in dye-sensitized solar cells (DSC), especially, with single electron outer sphere redox shuttle electrolyte. Insulating sub-nanometer oxide tunneling layers deposited by atomic layer deposition (ALD) are known to block the electron recombination, thereby leading to an increase in the open-circuit potential and the collection efficiency of the solar cell. A general perception in the DSC community is that any insulating oxide layer can block the recombination. However, in this work, it is unraveled that the insulating property of oxides alone is not sufficient. In addition, the properties such as the conduction band position and the oxidation state of the insulating oxide, the electronic structural modification induced to the underlying TiO2 mesoporous film, modification of surface charges (isoelectric point) and charge of the electrolyte species have to be considered. A complete photovoltaic study is done by depositing different cycles (by ALD) of four different insulating oxides (Ga2O3, ZrO2, Nb2O5, and Ta2O5) and their recombination characteristics, surface electronic properties, transport rate, and injection dynamics are investigated with a standard organic dye and Co2+/Co3+ redox mediator. A comparison is made with the conventional iodide/triiodide electrolyte.

In this paper we developed a recombination model for the steady state photoconductivity (SSP) with the assumption that the correlated dangling bond states (DB) act as the essential recombination centres and the electron recombination proceeds by tunneling from the conduction band tail states (TS) for n-type a-Si:H. The modeled temperature dependence of the SSP presents the main measured features, particularly the small activation energy and the thermal quenching.

We synthesized silver nanoparticles (Ag NPs) with particle sizes ∼6 nm, and also investigated the effect of Ag NPs on the performance of polymer solar cells. It is seen that Ag NPs improved power conversion efficiency (PCE) of poly[ N -9′′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole) (PCDTBT) solar cells. PCE increased from 0.65 to 1.72 with incorporation of Ag NPs. Hole and electron recombination time ( τ n ) was calculated with impedance spectroscopy as 0.4 ms for PCDTBT solar cells with nanoparticles and 1.26 ms for PCDTBT solar cells without nanoparticles.

This paper is concerned with the improvement of dye-sensitized solar cell (DSSC) efficiency upon ZnO-coating of the TiO2 electrode. Sol-gel ZnO of controlled amount by varying the number of sol drops during spin-coating is shown to increase the DSSC efficiency. The highest efficiency is obtained at a single sol drop with enhancement of 40%, while beyond this amount the efficiency falls down sharply to zero. Based on measured optical absorption spectra of the different dye-loaded electrodes, it is concluded that this amount of ZnO sol corresponds to the thinnest layer that can create the energy barrier to minimize the electron recombination rate without seriously affecting the dye adsorption efficiency of the TiO2 film.

A model for radiation-induced interface-trap buildup distinguishes among the contributions of hydrogen dimerization, electron recombination, and electric field mechanisms, quantitatively explaining time-dependent and true dose rate effects in irradiated bipolar isolation oxides. Hydrogen dimerization is the dominant ELDRS mechanism for devices exposed to medium H2 concentrations (1% per volume), whereas H2 cracking dominates as H2 concentration is increased further. Electron recombination mechanisms contribute at high dose rates ( >; 100 rad(SiO2)/s), but are not the dominant ELDRS mechanism at dose rates lower than 100 rad(SiO2)/s).

A facile approach to fabricate dye-sensitized solar cells (DSSCs) is demonstrated by depositing (001) oriented zinc oxide (ZnO) nanostructures on both glass and flexible substrates at room temperature using pulsed laser deposition. Unique crystallographic characteristics of ZnO combined with highly non-equilibrium state of pulsed laser-induced ablated species enabled highly crystalline ZnO nanostructures without aid of any chemically induced additives or organic/inorganic impurities at room temperature. Film morphology as well as internal surface area is tailored by varying ambient oxygen pressure and deposition time. It is revealed that the optimization of these two experimental factors was essential for achieving structure providing large surface area as well as efficient charge collection. The DSSCs with optimized ZnO photoanodes showed overall efficiencies of 3.89 and 3.4 % on glass and polyethylene naphthalate substrates, respectively, under AM 1.5G light illumination. The high conversion efficiencies are attributed to elongated electron lifetime and enhanced electrolyte diffusion in the high crystalline ZnO nanostructures, verified by intensity-modulated voltage spectroscopy and electrochemical impedance measurements. Electronic supplementary material The online version of this article (doi:10.1186/s11671-016-1437-2) contains supplementary material, which is available to authorized users.

The effect of N -(2-alkoxyphenyl) group in double rhodanine indoline dye on the performance of zinc oxide dye-sensitized solar cell was examined. Both J sc and V oc were improved by introducing long alkoxy group due to prevention of H-aggregates formation and inhibition of electron recombination from zinc oxide surface to electrolyte.

National High Technology Research and Development Program of China (863 Program) [2011AA050522]; Qinghai Science & Technology Department [2010-N-S03]; Ministry of Science & Technology (MOST) of China [2010DFB23160]

The absorbed light spectral composition determines the type of carrier generation: interband generation or mixed generation that also includes the generation of electrons from levels of the valence-band tail. The generation type affects the value and temperature dependence of the electron recombination rate in a-Si:H layered films. This effect is caused by a variation in the occupation of the levels of silicon dangling bonds and the valence band tail with electrons upon a change in the carrier generation type. As a result, in the case of mixed carrier generation in the investigated films with a low concentration of native dangling bonds, electron recombination in the films is slow and recombination at the levels of the valence-band tail can prevail up to room temperature.

Three organic dyes XS24–26 containing N,N-dimethylaniline and butoxybenzene have been designed, synthesized and applied in the dye-sensitized solar cells (DSSCs). The influence of secondary electron-donating groups on the performance of DSSCs is discussed. The dimethylaniline is beneficial to extend absorption spectrum, whereas butoxybenzene is useful to suppress electron recombination. XS26 containing butoxybenzene and thiophene unit gives the highest power efficiency η of 5.67%, with a JSC of 12.36 mA cm−2, VOC of 680 mV, and ff of 0.67.

A comb-like copolymer based on N-propylvinylimidazolium iodide (VImI) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) was synthesized. The VImI/PEGMA copolymer was used to prepare quasi-solid electrolytes. The charge transport and interfacial charge transfer of the dye-sensitized solar cells (DSSCs) based on the quasi-solid electrolytes were investigated using photocurrent density-voltage (J-V) curves, ionic conductivities, and impedance spectra. It was found that the copolymer plays an active role in decreasing the electron recombination at TiO2/electrolyte interface and increases the conduction band edge of TiO2. The photovoltaic characteristics of the DSSCs are therefore not determined entirely by the conductivity of the quasi-solid electrolyte. Based on the dependence of the open-circuit voltage on the VImI/PEGMA molar ratio, the decrease of recombination is primarily ascribed to the contribution of VImI segments. In addition, open-circuit voltage decay (OCVD) and photocurrent transient results indicate that the introduction of the copolymer not only extends the electron lifetime but also tunes the energy distribution of the localized electrons. When the VImI/PEGMA molar ratio reaches 5.0 and the mass fraction of copolymer in the quasi-solid electrolyte is 50%, the DSSC yields an energy conversion efficiency of 4.10% under an illumination intensity of 100 mW·cm-2. [Article] doi: 10.3866/PKU.WHXB201202233 www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2012, 28 (5), 1139-1145 May Received: November 21, 2011; Revised: February 1, 2012; Published on Web: February 23, 2012. ∗Corresponding authors. SUN Zhe, Email: zhesun@tjut.edu.cn; Tel: +86-22-60214259. XUE Song, Email: xuesong@ustc.edu.cn; Tel: +86-22-60214250. The project was supported by the National Natural Science Foundation of China (21003096, 21103123). 国家自然科学基金(21003096, 21103123)资助项目 C Editorial office of Acta Physico-Chimica Sinica 1139 Acta Phys. -Chim. Sin. 2012 Vol.28 1 引 言 染料敏化太阳能电池(DSSCs)是近20年发展起 来的新型“激子”薄膜电池.此类电池不必采用高 纯度半导体或稀土材料,能够同时实现光伏器件的 低成本和高效率. 目前, 染料敏化太阳能电池的实 验室光电转换效率已经达到 12.3%,电池组件效率 也超过8%.染料敏化电池普遍采用液态电解质,电 解液的低粘度和氧化还原电对的高扩散系数保证 了电池内部的有效电荷分离和较高的光电转换效 率. 但是, 基于液态电解质的染料敏化电池在实际 应用中存在难于封装、有机溶剂挥发泄漏等问题, 直接影响了电池的使用寿命. 为解决这些问题, 研 究者已经着手开发固态和准固态电解质,包括有机 空穴传输材料、p型半导体、聚合物电解质、聚合物 凝胶电解质等. 其中, 聚合物凝胶电解质是利用 高分子聚合物对电解液进行凝胶化处理得到的准 固态电解质. 此类电解质虽不具有流动性, 但电荷 输运机制类似于液态电解质,因此在解决电池的长 期使用问题的同时,可以获得与液态电解质近似的 光电转换效率. 目前,准固态电解质中使用的聚合物材料主要 有丙烯酸-乙二醇共聚物,聚氧乙烯,聚偏氟乙烯, 聚甲基硅氧烷等. 这些材料虽然能够对电解质 进行有效地凝胶化, 但聚合物只起到凝胶骨架作 用,对促进电荷分离提高电池性能没有贡献.小分 子咪唑碘盐已被证实能够在TiO2/电解质界面形成 Helmholtz双电层,抑制电子复合从而提高电荷收集 效率. 为此,研究者将咪唑碘盐作为修饰基团引入 聚合物端基或侧链以提高敏化电池的光伏性能. 在本文中, 我们直接将咪唑碘盐引入聚合物主链, 合成了具有梳状结构的乙烯基咪唑碘盐/聚乙二醇 单甲醚甲基丙烯酸酯共聚物,并制备了基于此共聚 物的准固态电解质.在表征共聚物及其电解质结构 的同时,本文着重研究了基于此电解质的敏化电池 的光伏性能与共聚物组成和浓度的关系,利用电化 学阻抗谱分析了准固态电池的电荷输运与界面电 子转移特性,讨论了共聚物对TiO2薄膜的电子寿命 的影响. 2 实验部分 2.1 试剂和仪器 聚乙二醇单甲醚甲基丙烯酸酯(PEGMA, Mw约 为300 g·mol-1, Sigma-Aldrich);导电玻璃(FTO, 15 Ω· □,大连七色光太阳能科技开发有限公司); N719染 料((TBA)2-cis-Ru(Hdcbpy)2-(NCS)2, Solaronix, 瑞士); 氯铂酸(H2PtCl6, Sigma-Aldrich). 乙烯基咪唑(VIm), 1-碘丙烷, 偶氮二异丁腈(AIBN), γ-丁内酯(GBL), 碘和碘化锂均为市售分析纯试剂. 共聚物及电解 质的红外光谱采用傅里叶变换红外(FT-IR)光谱仪 (Avatar-370DTGS, Thermo Nicolet公司, 美国)测得. 利用电化学工作站(LK2005B,天津兰立科化学电子 有限公司)分别测定了电解质的电导率和敏化电池

Upon the formation of the surface complexes of dicyanomethylene compounds (TCNX: TCNE, TCNQ, and TCNAQ) with TiO2 nanoparticles, new visible light absorption bands appear due to interfacial charge-transfer transitions from the TCNX adsorbates to the conduction band of TiO2. The charge-transfer absorption band is significantly changed depending on the kind of TCNX. The spectral region is extended to the near-IR region with increase in the π-conjugation length of TCNX. Density functional theory calculations using simple model compounds Ti(OH)3-O-TCNX– well reproduce the charge-transfer bands and the TCNX dependence and the experimentally observed vibrational spectrum of the TiO2-TCNQ surface complex. We then model the geminate electron recombination from TiO2 to the HOMO level of the TCNX moiety immediately following the charge-transfer transitions. The computed result indicates that the rate of the recombination process is significantly dependent on the kind of TCNX, increasing with the extent of the π-con...

Ministry of Science & Technology (MOST) of China [2010DFB23160]; research fund for the doctoral program of higher education of China [20090002110010]

Research on the flexible dye-sensitized solar cells (DSCs) has been more and more extensively conducted during the recent years both academically and comercially for the sake of its further reduced expense and even broader application. However, significant promotion of electron transport properties and consequently the photovoltaic performances of such devices are perpetually hindered by the key problem that the poor heat tolerance of the plastic substrates employed in flexible DSCs makes high-temperature sintering of the photoanode films impossible. Based on a brief overview of the current state of research on flexible DSCs, including new materials and delicate processing techniques, and the research results from the author’s own group, this chapter specially treats the profound mechanistic issue of electron transport and recombination in flexible DSCs, which is rarely discussed and relatively less well understood up to now. It is pointed out that the electron transport and recombination dominate photovoltaic performance of the flexible DSCs and suppressing the recombination of injected electrons with electrolyte redox species is of crucial sense for performance promotion. Besides, the methods for restraining electron recombination are proposed and the developing trend and prospects of flexible DSCs are also presented.

We report on our recent studies of dissociative recombination (DR) employing two different fragment imaging detection techniques at the TSR storage ring in Heidelberg, Germany. Principles of an upgraded 3D optical system and the new energy-sensitive multistrip detector (EMU) are explained together with possible applications in reaction dynamics studies. With the EMU imaging detector we succeeded to observe the branching ratios after DR of deuterated hydronium ions D(3)O(+) at energies of 0-0.5 and 4-21 eV. The branching ratios are almost constant at low energies while above 6 eV both oxygen-producing channels O + D + D + D and O + D(2) + D strongly increase and dominate by about 85% at 11 eV. To demonstrate further capabilities of our fragment imaging detectors, we also summarize some of our additional recent studies on DR of molecular ions important for astrophysics as well as for fundamental unimolecular dynamics.

Detailed measurements employing a combination of a cryogenic flowing afterglow with Langmuir probe (Cryo-FALP II) and a stationary afterglow with near-infrared absorption spectroscopy (SA-CRDS) show that binary electron recombination of para-H3(+) and ortho-H3(+) ions occurs with significantly different rate coefficients, (p)αbin and (o)αbin, especially at very low temperatures. The measurements cover temperatures from 60 K to 300 K. At the lowest temperature of 60 K, recombination of para-H3(+) is at least three times faster than that of ortho-H3(+) ((p)αbin=(1.8±0.4)×10(-7) cm(3) s(-1) vs. (o)αbin=(0-0 (+5))×10(-8) cm(3) s(-1)).

Poly(3,4-ethylenedioxypyrrole) (PEDOP), combined with metal-free organic sensitizers, is efficiently used for the first time as the hole-transporting material in solid-state dye-sensitized solar cells. Devices employing PEDOP as the hole conductor and D35 or D21 L6 as the sensitizer show a ten-times-higher energy-conversion efficiency (of 4.5% and 3.3%, respectively) compared to Ru-Z907-based devices. This is due to the efficient suppression of electron recombination.

The two mechanisms known for the production of cometary C('D) atoms, namely the dissociative electron recombination of CO + ions and the photodissociation of CO molecules, have been examined to ascertain whether these mechanisms can produce the observed brightnesses of the comae of Comet 1P/Halley, Comet C/1975 V1 (Comet West 1976 VI) and Comet C/1979 Yl (Comet Bradfield 1979 X) in the C I ( 1 D- 1 P o ) line at 1931 A on specific dates. The brightnesses computed from these mechanisms for the respective comets are compared with those quoted in the literature. It is found that the latter of the above two mechanisms can account for the observed brightnesses of these comets in the C I ( 1 D- 1 P o h ) line. A valid, hitherto undiscussed reaction mechanism not involving COH for the production of cometary C( 1 D) atoms is suggested.

ZnO@SnO2 multilayered network was deposited on fluorine doped tin oxide (FTO) glass and applied as photoanode in dye sensitized solar cells whose functional performances are compared with single oxide-based photoanodes made of SnO2 nanoparticles and ZnO microparticles. Multi-oxide photoanodes provide for enhanced photoconversion efficiency (3.31%) as compared with bare SnO2 nanoparticles (1.06%) and ZnO microparticles (1.04%). Improved functional performances of the ZnO@SnO2 layered network are ascribable to partial inhibition of back electron transfer from SnO2 to the redox electrolyte, guaranteed by the ZnO, which acts as a capping layer for the underlying SnO2.

The effect of a ZnO compact blocking layer (BL) in dye-sensitized solar cells (DSSCs) based on ZnO photoanodes is investigated. BL is generated through spray deposition onto fluorine-doped tin oxide (FTO) conducting glass before the deposition of a ZnO active layer. The functional properties of dye-sensitized solar cells (DSSCs) are then investigated as a function of the thickness of the BL for two different kinds of ZnO active layer, i.e., hierarchically self-assembled nanoparticles and microcubes composed of closely packed ZnO sheets. Presence of BL leads to the improvement of photoconversion efficiency (PCE), by physically insulating the electrolyte and the FTO. This effect increases at increasing BL thickness up to around 800 nm, while thicker BL results in reduced cell performance. Remarkable increase in Jsc is recorded, which doubles as compared to cells without blocking layer, leading to PCE as high as 5.6% in the best cell under one sun irradiation (AM 1.5 G, 100 mW cm(-2)). Electrochemical impedance spectroscopy (EIS) elucidates the mechanism boosting the functional features of the cells with BL, which relies with enhanced chemical capacitance together with an almost unchanged recombination resistance, which are reflected in an increased electron lifetime. The results foresee a straightforward way to significantly improve the performance of ZnO-based DSSCs.

A two-dimensional time-dependent model of non-self-sustained dc and RF discharges is used for the analysis of recent experiments in optically-pumped non-equilibrium plasmas. The analysis shows that non-self-sustained dc and RF discharges can be successfully used for measurements of the electron production rate, electron recombination rate, and electron density in these plasmas. The inferred rate of electron production per unit volume by the associative ionization mechanism is S0 = 1.0 × 10 15 cm −3 s −1 and S0 = 2.2 × 10 14 cm −3 s −1 in CO/Ar = 2/100 and in CO/N2 = 2/100 plasmas, respectively. The inferred electron–ion recombination rate coefficients are β> 6.0 × 10 −6 cm 3 s −1 and β = (7.5 ± 1.5) × 10 −6 cm 3 s −1 in CO/Ar = 2/100 mixtures at P = 100 Torr and 20 Torr, respectively. In CO/Ar = 2/100 mixtures with a 0.05–0.1 Torr admixture of O2 at P = 100 Torr and 20 Torr, the inferred recombination rate coefficients are β = (1.5 ± 0.3) × 10 −8 cm 3 s −1 and β = (5.1 ± 2.9) × 10 −8 cm 3 s −1 , respectively. Finally, the inferred electron density in optically-pumped CO/Ar/O2 plasmas at the laser beam axis is ne = (1.7 ± 0.2) × 10 11 cm −3 at P = 100 Torr and ne = (6.2 ± 0.8) × 10 10 cm −3 at P = 20 Torr. These results demonstrate that the electron density in optically-pumped CO/Ar plasmas can be controlled and significantly increased by adding small amounts (up to ∼0.1%) of species such as O2 and NO, which result in the reduction of the electron–ion recombination rate.

Despite many experimental efforts over several decades, no consensus has been reached concerning the rate of dissociative recombination of H3+. We review the current status concerning different experimental approaches to the measurement of the cross–section, rate coefficient and branching ratios in electron recombination of H3+.