Electron Transport Capability Research Articles

Defect processes in F and Cl doped anatase TiO2

Titanium dioxide represents one of the most widely studied transition metal oxides due to its high chemical stability, non-toxicity, abundance, electron transport capability in many classes of optoelectronic devices and excellent photocatalytic properties. Nevertheless, the wide bang gap of pristine oxide reduces its electron transport ability and photocatalytic activity. Doping with halides and other elements has been proven an efficient defect engineering strategy in order to reduce the band gap and maximize the photocatalytic activity. In the present study, we apply Density Functional Theory to investigate the influence of fluorine and chlorine doping on the electronic properties of TiO2. Furthermore, we present a complete investigation of spin polarized density functional theory of the (001) surface doped with F and Cl in order to elaborate changes in the electronic structure and compare them with the bulk TiO2.

Composites formed from tungsten trioxide and graphene oxide for the next generation of electrochromic interfaces

Abstract Thin films of electrochromic (EC) materials are being used as energy saving platforms. However, manufacturing high quality of such films while ensuring their superior stability and high coloration availability, as well as their persistency in diverse conditions of temperature and/or illumination, is challenging. Herein we proposed to create the next generation of composites that display EC characteristics using a user-controlled manufacturing strategy based on Matrix Assisted Pulsed Laser Evaporation (MAPLE). In our approach, tungsten trioxide and graphene oxide were employed as starting materials, with MAPLE controlling material deposition conditions and overall composites’ thickness. The resulting EC composites were characterized for their chemical and physical properties using Fourier Transform Infrared Spectroscopy and Energy Dispersive Spectroscopy, and Optical and Atomic Force Microscopy respectively, with changes in their electrochemical characteristics being evaluated by cyclic voltammetry and related to film thickness through the use of spectrophotometry. It was found that MAPLE deposition conditions allow for formation of composites that display enhanced electron transport capabilities and high energy efficiency at their interfaces; further, it was found that MAPLE allowed for uniform films production, of controlled thickness as well as eliminated possible impurities normally associated with other methods used for EC films production such as sputtering, sol–gel or electrodeposition, and chemical wet deposition respectively. Our work could potentially provide a user-controlled synthesis and manufacturing strategy for the formation of next generation of EC thin films that have minimum interfacial defects while possessing maximum conversion efficiency to thus influence and/or dictate their energy saving profiles.

Efficient halide perovskite light-emitting diodes with emissive layer consisted of multilayer coatings

Perovskite light-emitting diodes (PeLEDs) with multilayer coatings consisted of CsPbBr3 and 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene as the emissive layer are demonstrated. The effects of the multilayer coatings upon both the electroluminescent performance and the device stability are investigated. The PeLEDs with a coating pair number of 4 (four-pair PeLEDs) obtain a maximum current efficiency of 9.16 cd/A and a maximum external quantum efficiency of 2.37%, corresponding to more than 4-fold enhancement to those of the control PeLEDs. Furthermore, the half-lifetime of the four-pair PeLEDs is about 50 times longer than that of the control PeLEDs. Such enhancements are attributed to the improved film morphology, enhanced electron injection and transport capability, widened exciton formation zone, and better exciton confinement.

Solution-processable GO/rGO: Preparation, functionalization, self-assembly and applications in smart information devices

Graphene, as a kind of nano and mesoscopic molecule which consists of one-atom-thick planar sheet comprising sp2-bonded carbon structure with exceptionally high crystal and electronic quality, shows hierarchical different physical and chemical properties and has been emerged as a rapidly rising star in the field of material science. Graphene has caused much concern in many areas of science and technology due to its remarkable properties. These properties include extraordinary mechanic performances, high specific surface areas and electron transport capabilities. These unique physicochemical properties suggest that graphene has great potential for providing new approaches and critical improvements in the field of information devices. In recent years, many reviews focusing on graphene and related materials have been published. In addition, several reviews with particular emphasis on information devices based on graphene related materials have been reported. One specific branch of graphene research deals with graphene oxide (GO) and reduced graphene oxide (rGO). GO can be considered as a precursor to graphene synthesis by either chemical or thermal/light reduction processes. GO consists of a single-layer of graphite oxide and is usually produced by the chemical treatment of graphite through oxidation, with subsequent dispersion and exfoliation in water or suitable organic solvents. With respect to its structure, there have been several structural models proposed over the years. These assume the presence of various oxygen functional groups in the GO. The oxygen functional groups have been identified as mostly in the form of hydroxyl and epoxy groups on the basal plane, with smaller amounts of carboxyl, carbonyl, phenol, lactone, and quinone at the sheet edges. The chemical reduction of graphene oxide is a promising route towards the large scale production of graphene for commercial applications. The electrical conductivity of the functionalized graphene has been observed to decrease significantly compared to pure graphene, moreover, the surface area of the functionalized graphene prepared by covalent and non-covalent techniques decreases significantly due to the destructive chemical oxidation of flake graphite followed by sonication, functionalization and chemical reduction. However, complementary to the inherent properties of graphene, functionalization or hybridization from GO and rGO can substantially improve the performance of these materials in the information devices. The functionalization of graphene can be performed by covalent and noncovalent modification techniques. In both cases, surface modification and chemical selective reduction of graphene oxide have been carried out to obtain solution-processable graphene related materials. It has been found that both the covalent and noncovalent modification techniques are very effective in the preparation of solution-processable graphene related materials. In this review, we outline the developments of GO/rGO related chemical reactions, functionalization routes and self-assembled methods in the viewpoint of hierarchical chemistry. The dispersibility and interactions of nanosheets involved in thin film technology are summarized here to better understanding the GO/rGO ink formula, film forming and nanostructure. Finally, the applications of GO/rGO related soluble processed materials in smart information devices such as information display, information storage and neuromorphic are discussed as well as the current challenges and several possible future research directions.

MXene-decorated SnS2/Sn3S4 hybrid as anode material for high-rate lithium-ion batteries

The combination of transitional metal dichalcogenides with MXene is an effective strategy to explore high-performance anode materials for lithium-ion batteries (LIBs). In this work, SnS2/Sn3S4 hybrid decorated on Ti3C2 MXene (S-TC) was prepared through a facile solvothermal and calcination process. The multi-layered Ti3C2 matrix improves the electron transport capability, inhibits the aggregation and accommodates the volume change of SnS2/Sn3S4 hybrid, while the SnS2/Sn3S4 hybrid confined in the multilayer stacks serves as a spacer to decrease the tendency of layer restacking and improves the limited capacities of Ti3C2. Besides, the nano-sized SnS2/Sn3S4 hybrid with high specific surface area also enhances the contact between electrolyte and electrode. When used as anode for LIBs, S-TC demonstrates a good cycling stability (462.3 mAh g−1 at 100 mA g−1 after 100 cycles) and superior rate performance (216.5 mAh g−1 at 5000 mA g−1). The strategy in this work should provide a new insight into fabricating novel MXene-based anode material for high-rate LIBs.

Observing electron transport and percolation in selected bulk heterojunctions bearing fullerene derivatives, non-fullerene small molecules, and polymeric acceptors

We systematically study how electrons achieve percolation pathways in a bulk-heterojunction (BHJ) blend as the weight fraction of the electron acceptor is altered. Three different classes of BHJs are explored: BHJs that contain (1) fullerene-based acceptors, (2) non-fullerene small molecules, and (3) polymer acceptors. The nano-topologies of acceptors in (1) to (3) can be approximately associated with spheres, oblates (plates) and prolates (long rods), respectively. We discover that the weight fraction of the acceptor for electron percolation to complete is successively reduced in the order of fullerenes (0.32), non-fullerene (NF) small molecules (0.25), and polymers (0.11). A new parameter, namely, the effective volume fraction, χ, is introduced to quantify the fraction of the acceptor moieties that can contribute to electron transport in the BHJs. The electron percolation regions can be fitted with a model that considers the shapes of the acceptors and their χ in the BHJs. An all-polymer BHJ containing PTB7-Th:N2200 exhibits the largest χ (0.6–0.8), indicating N2200 acceptors are the most effective in transportation of electrons. All-polymer BHJs can better preserve their electron transport capability arising from composition variations, and they are immuned from the introduction of inert materials or the exposure of moisture, in stark contrast to fullerene-based BHJs. Our results correlate the electron transport behaviors to the nano-topologies of acceptors for BHJ cells, and offer guidance to tune the compositions and understand the nano-morphology of BHJ cells using different classes of acceptors.

A high-performance lithium-ion capacitor with carbonized NiCo2O4 anode and vertically-aligned carbon nanoflakes cathode

Lithium ion capacitors (LICs) are energy storage devices integrating the complementary features of both supercapacitors and lithium ion batteries to simultaneously reach high energy and power densities. One of the major challenges in LIC technology is the kinetic imbalance between the faradaic insertion anode and capacitive cathode. Therefore, the design of electrode materials is crucial to enhance the rate performance of anode and the capacitance of the cathode in LIC devices. In this work, novel LICs were demonstrated with nanostructured cathode and anode. A vertically-aligned carbon nanoflakes (VACNFs) cathode provided high electrochemically active surface area and excellent conductivity, while a metal organic framework (MOF) derived carbonized nickel cobalt oxide (cNiCo2O4) anode ensured fast conversion reactions and remarkable cyclability. Electrochemical characterization of individual electrode confirmed that both electrodes exhibited good electron and ion transport capability. The LICs were fabricated with optimized electrode active materials loading to deliver high energy densities at desired charge/discharge rates. The devices exhibited energy density up to 136.9 W h/kg (at 200 W/kg). At higher power density of 40 kW/kg, under which a full charge-discharge can be finished within 4 s, the LICs could still deliver an energy density of 26.44 W h/kg. The devices also showed a good cycle stability (≈90% capacitance retention after 9000 cycles, under current density of 4 A/g) within the voltage range of 1–4.2 V.

Efficient Enhancement of Electron Transport and Collection Capability in PTB7:PC71 BM-based Solar Cells Enabled by Sulforhodamine Cathode Interlayers.

Development of low-cost water-/alcohol-soluble interfacial materials is a crucial issue to promote the commercialization of polymer solar cells (PSCs). Herein, two derivatives of low-cost rhodamine, called sulforhodamine 101 (SR101) and sulforhodamine B (SRB), are applied as cathode interfacial layers (CILs) to effectively improve the charge-carrier transportation and collection, reduce the work function (WF) of Al counter electrode, and decrease the series resistance and charge recombination in the PSCs. As a result, SR101-based devices show excellent performance with the highest power conversion efficiency (PCE) of 9.10 %, superior to that of both the control devices with MeOH/Al and Ca/Al. Notably, sulforhodamine is commercially available with low cost and great solution-processability. This work demonstrates that sulforhodamine has a great potential as a CIL material,which is suitable for the large-area fabrication process and commercialization of highly efficient PSCs.

Electrochemical sensing performance of Eu-BTC and Er-BTC frameworks toward Sunset Yellow

Two lanthanide metal-organic frameworks (Ln-MOFs) using 1,3,5-benzenetricarboxylic acid (H3BTC) and Ln(III) nitrate hydrate (Ln = Eu, Er) as precursors have been prepared through a one-step solvothermal approach. The as-synthesized compounds were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy, confirming that the targeted Ln-MOFs were successfully synthesised, with a straw-sheaf appearance. Their sensing properties were studied using cyclic voltammetry and electrochemical impedance spectroscopy, and the results showed that the prepared Ln-BTCs possessed larger electrochemical-response areas and stronger electron-transport capability, especially the Er-BTC. The oxidation behaviour of Sunset Yellow was investigated, and it was found that the Er-BTC exhibited a superior enhancement effect. Chronocoulometry was used to prove that Er-BTC more strongly adsorbs Sunset Yellow, resulting in a larger electrochemical response signal. The novel Sunset Yellow sensor exhibited a linear response in the range of 0.2–100 nM with a low limit of detection (0.05 nM, S/N = 3), and was applied in drink samples. The results were validated by high-performance liquid chromatography, indicating this sensor is a promising tool for Sunset Yellow detection.

Ga-doped ZnO nanorod scaffold for high-performance, hole-transport-layer-free, self-powered CH3NH3PbI3 perovskite photodetectors

The use of aligned one-dimensional nanostructures as scaffolds in organic-inorganic hybrid perovskite photodetectors (PDs) has attracted significant attention due to their large surface area-to-volume ratio and efficient electron transport capability in the radial direction. Here, we report CH3NH3PbI3 (MAPbI3) perovskite photodetectors (PDs) with Ga-doped ZnO nanorods (GZO NRs), prepared by the water bath method, as a scaffold-structure electron transport layer (ETL). Our MoO3 hole transport layer (HTL) based perovskite PDs using GZO NRs as a scaffold showed a larger light/dark current (Iph/Idark) ratio, higher responsivity and detectivity than those of the undoped ZnO NRs/MAPbI3 devices at zero bias. These enhancements are attributed to the incorporation of Ga atoms into the ZnO NRs, which reduce the density defect states of ZnO NRs and improves the performance of MAPbI3 perovskite PDs. In addition, by taking advantage of the GZO NRs scaffold structure, a HTL-free perovskite PD was prepared by using graphite electrodes. The graphite-connected device shows self-powered PD performances with an Iph/Idark ratio of ~2.5 × 103, responsivity of above 0.3 A/W and detectivity of 1.3 × 1012 Jones, all of which are comparable with those of MoO3 HTL based perovskite PDs.

Self-healing silicon-sodium alginate-polyaniline composites originated from the enhancement hydrogen bonding for lithium-ion battery: A combined simulation and experiment study

Silicon anode suffers from poor intrinsic conductivity and dramatic volume change during discharge/charge process, which hinders its commercialization for high energy density lithium-ion batteries. To address these challenges, silicon-sodium alginate-polyaniline composites are rationally designed and synthesized via in-situ polymerization. A hydrogen bond self-healing process occurs during lithiation and delithiation to accommodate the strong volumetric modification, so that the composites perform excellent electrochemical performance, with a capacity of 1099.5 mAh·g−1 after 200 cycles at the current density of 1.0 A·g−1. In view of the density functional theory calculations, the synergy effect of sodium alginate and polyaniline enhances the hydrogen bonding of the silicon and polymers, increases the electron transport capability, and results in excellent electrical, mechanical integrity and conductivity of the electrodes. Our work not only provides a facile procedure to prepare unique conducting three dimensional network structured composites as a commercial anode but also reveals the mechanism that the silicon nanoparticles avoids electrode pulverization via hydrogen bonding self-healing process.

2D-Bi2MoO6/2D-g-C3N4 nanosheet heterojunction composite: synthesis and enhanced visible light photocatalytic mechanism

In this study, a novel 2D Bi2MoO6 nanosheet/2D g-C3N4 nanosheet heterojunction composite was fabricated through a hydrothermal strategy. Afterwards, physicochemical properties of the composite were systematically detected by a series of measurements. In addition, photocatalytic activity was evaluated by the degradation of rhodamine B, methylene blue, Amido black 10B and malachite green. The results showed that Bi2MoO6/g-C3N4 possessed higher photocatalytic efficiency than that of the pristine Bi2MoO6 and g-C3N4 sample under visible irradiation. This phenomenon could be attributed to the combination of Bi2MoO6 and g-C3N4 as well as the unique 2D/2D heterostructure. Also, the as-fabricated Bi2MoO6/g-C3N4 composite possessed higher surface area, narrower bandgap energy, larger electron transport capability and longer charge carrier lifetime. Furthermore, the enhanced visible-light-driven photocatalytic mechanism was proposed and confirmed, which was mainly ascribed to the Z-scheme structure. That is, the photogenerated electrons (e−) in the conduction band (CB) of Bi2MoO6 and photogenerated holes (h+) in the valence band (VB) of g-C3N4 could combine with each other quickly, so that the e− in the CB of g-C3N4 and h+ in the VB of Bi2MoO6 participated in reduction and oxidation reactions, respectively. Also, this composite exhibited superior physicochemical stability. Hence, it could be applied in advanced wastewater treatment.

Multi-mode photocatalytic performances of CdS QDs modified CdIn2S4/CdWO4 nanocomposites with high electron transfer ability

In general, quantum dots have the property of generating a plurality of charge carriers using hot electrons or using a single high-energy photon to improve the photocatalytic properties of the material. In this paper, CdS QDs@CdIn2S4/CdWO4 modified by CdS QDs was synthesized by the microwave-assisted hydrothermal method, and its composition, crystal structure, morphology, and surface physicochemical properties were well characterized. Electron microscopy results showed that CdS QDs@CdIn2S4/CdWO4 composite material exhibited a sheet structure with a length of ca. 350 nm and a width of ca. 50 nm, and CdS QDs uniformly distributes with a diameter of about 5 nm on the sheet structure. UV-visible diffuse reflectance tests showed that the combination of CdS QDs and CdIn2S4 can extend the light absorption range of CdWO4 to the visible region. Photoluminescence spectroscopy confirmed that CdS QDs had efficient electron transport capabilities. The multi-mode photocatalytic activity of CdS QDs@CdIn2S4/CdWO4 showed an excellent ability to degrade organic pollutants. Under the conditions of no co-catalyst and Na2S-Na2SO3 as the sacrificial agent, the hydrogen production of CdS QDs@CdIn2S4/CdWO4 can reach 221.3 μmol g−1 when exposed to visible light (λ > 420 nm) for 8 h.

2-Methyl-9,10-bis(naphthalen-2-yl)anthracene doped rubidium carbonate as an effective electron injecting interlayer on indium-tin oxide cathode in inverted bottom-emission organic light-emitting diodes

2-Methyl-9,10-bis(naphthalen-2-yl)anthracene doped rubidium carbonate (MADN:Rb2CO3) is used as an effective electron injecting interlayer on an indium-tin oxide (ITO) cathode for inverted bottom-emission organic light-emitting diodes (IBOLEDs). At a Rb2CO3 doping concentration of 20% in MADN, the device exhibits enhanced characteristics, some of which are turn-on voltage, luminance at a given current density, and current efficiency. The attained performance is better than that of the device using lithium fluoride (LiF) as an n-type dopant. Space-charge-limited current acknowledges improved electrical properties of Rb2CO3 doped MADN. Ultraviolet and X-ray photoelectron spectroscopy investigation unveils an interfacial dipole layer induced by charge transfer between Rb2CO3 and ITO, leading to a lowered ITO work function and an electron injection barrier. The improved electron injection and transport capabilities contribute to better charge balance in IBOLED, thus resulting in advanced luminance efficiency. In addition, the morphology stability of organic films is also amended, which benefits long-term reliability under operationally induced thermal stress. Moreover, the effectiveness of using Rb2CO3:MADN as an electron injecting layer for IBOLEDs is superior to many of its alkali-based counterparts demonstrated in the literature, with high compatibility with different types of sophisticated ITO-based IBOLEDs.

Inorganic iron-sulfur clusters enhance electron transport when used for wiring the NAD-glucose dehydrogenase based redox system

Wiring the active site of an enzyme directly to an electrode is the key to ensuring efficient electron transfer for the proper performance of enzyme-based bioelectronic systems. Iron-sulfur complexes, the first link between proteins and mediating molecules in the biological electron transport chain(s), possess an intrinsic electron transport capability. The authors demonstrate the application of inorganic iron-sulfur clusters (Fe-S) viz. FeS, FeS2, Fe2S3, and Fe3S4, as molecular wires to mediate electron transport between a glucose-selective redox enzyme and the gold electrode. It is shown that Fe-S can emulate the functionality of the natural electron transport chain. Voltammetric studies indicate a significant improvement in electron transport, surface coverage, and resilience achieved by the Fe-S-based glucose anodes when compared to a conventional pyrroloquinoline quinone (PQQ)-based electrode. The Fe-S-based glucose anodes showed glucose oxidation at a potential of +0.5 V vs. Ag/AgCl with Tris-HCl buffer (pH 8) acting as a carrier. The current densities positively correlated with the concentrations of glucose in the range 0.1–100 mM displaying detection limits of 0.77 mM (FeS), 1.22 mM (FeS2), 2.95 mM (Fe2S3), and 14.57 mM (Fe3S4). The metal-anchorable sulfur atom, the strong π-coordinating iron atom, the favorable redox properties, low cost, and natural abundance make Fe-S an excellent electron-mediating relay capable of wiring redox active sites to electrode surfaces.Graphical abstractSchematic representation of inorganic iron-sulfur clusters used as molecular wires to facilitate direct electron transfer between NAD-glucose dehydrogenase and the gold electrode. The iron-sulfur based glucose anodes improve current response to selectively sense glucose concentrations in the range 0.1–100 mM.

Development of Functionalized "UiO-66 MOF" Embedded Cellulose Nanocomposites for Photoelectrochemical Water Splitting

Economic distress resulting from global dependence on diminishing fossil fuels that adversely impact the environment has led to increased interest in alternative green energy technologies. The photoelectrochemical cell (PEC), provides an attractive green energy solution that incorporates semiconductor materials capable of absorbing visible light to power the splitting of water and create H2 gas, a clean fuel source. PEC systems today, however, are not yet commercially viable due to a lack in efficiency, stability and cost effectiveness. Therefore, the goal of this work is to create a novel, low price semiconducting material to be used as an electrode in a PEC system. This will be accomplished by incorporating the zirconium based Metal Organic Framework (MOF) UiO-66 into a celllulostic network to create a flexible, semiconducting material. The UiO-66 MOF offers a combination of defect sites on the Zr metal cluster and an aromatic linker allowing for light absorption coupled with efficient charge transport. Unfortunately, UiO-66 absorbs in the UV region (2% of sunlight), but its high stability and conjugated organic ligands make it ideal for photosensitization. Simple post synthetic modifications (PSM) can be done to improve light harvesting and electron transport capabilities within the cellulose network. Modifications incorporated in this work include the use of polyaniline crosslinkers as well as metal nanoparticle doping. Conductivity of each material was characterized using a four point probe and measuring current response to applied stepwise voltage. PEC performance was determined by illuminating cell with light and measuring voltage, current and product evolution. Overall, this work provides a foundational design of low cost working electrodes for use in PEC systems, that can lead to future modifications to optimize cell performance.

Enhanced UV photoresponse with Au nanoparticles incorporated rGO/Si heterostructure

In this work, we demonstrated Au nanoparticles incorporated reduced graphene oxide (rGO)/Si heterostructure based UV photodetector. The pristine and Au nanoparticles incorporated heterostructure was analyzed and characterized by x-ray photo electron spectroscopy (XPS), Current- Voltage (I-V) characteristics and UV photo detective properties were examined by using UV light emitting diode (LED) with 382 nm wavelengths. The UV photoresponse properties revealed that the Au-rGO/Si heterostructure showed much better photoresponse activity toward UV light than pristine rGO/Si. The experimental results clearly revealed that the photoresponse of Au-rGO/Si heterostructure can be effectively enhanced by 30 times at 382 nm wavelength over pristine rGO/Si. The effect of rGO thickness on performance of UV photodetector was also examined. The improved photoresponse was attributed to localized surface plasmon resonance, in addition high electron transport capability of rGO number of photoexcited electrons collected at interface.

Engineered hetero structured arrays of ZnO NanoX (X = discs, rods and wires) and CdTe quantum dots for advanced electron transport applications

Novel hetero structured arrays of CdTe quantum dots capped ZnO nanostructures were successfully prepared through a three tier process. C-axis oriented ZnO nanostructures, namely ZnO nanox (where, x=discs, rods and wires), were prepared on glass and ITO substrates by employing simple, template free and low temperature solvothermal methods. CdTe quantum dots were synthesized subsequently through an organometallic route. ITO/ZnO NanoX/CdTe heterostructured arrays were finally developed, by capping ZnO nanostructured arrays with CdTe quantum dots by using 3-mercaptopropionic acid. The crystalline, structural, morphological and optical features of the individual nanostructures and the heterostructured arrays were investigated by using XRD, HR-TEM, SEM, EDAX, AFM, UV and PL. The role of solvents, solution concentration and temperature on deciding the final morphologies in solvothermal syntheses were studied and the possible growth mechanism of the different nanostructure arrays were proposed. The comparative electron transport studies of the ITO/ZnO NanoX/CdTe heterostructure arrays were carried out. Electrochromic display units having fast electron transport capabilities were developed. The study put forth many futuristic applications of these hetero structured assemblies in wide spectrum of scientific and industrial disciplines, particularly in the areas where a fast electron transport is required.

Non-Fullerene Acceptor-Based Solar Cells: From Structural Design to Interface Charge Separation and Charge Transport.

The development of non-fullerene small molecule as electron acceptors is critical for overcoming the shortcomings of fullerene and its derivatives (such as limited absorption of light, poor morphological stability and high cost). We investigated the electronic and optical properties of the two selected promising non-fullerene acceptors (NFAs), IDIC and IDTBR, and five conjugated donor polymers using quantum-chemical method (QM). Based on the optimized structures of the studied NFAs and the polymers, the ten donor/acceptor (D/A) interfaces were constructed and investigated using QM and Marcus semi-classical model. Firstly, for the two NFAs, IDTBR displays better electron transport capability, better optical absorption ability, and much greater electron mobility than IDIC. Secondly, the configurations of D/A yield the more bathochromic-shifted and broader sunlight absorption spectra than the single moiety. Surprisingly, although IDTBR has better optical properties than IDIC, the IDIC-based interfaces possess better electron injection abilities, optical absorption properties, smaller exciton binding energies and more effective electronic separation than the IDTBR-based interfaces. Finally, all the polymer/IDIC interfaces exhibit large charge separation rate (KCS) (up to 1012–1014 s−1) and low charge recombination rate (KCR) (<106 s−1), which are more likely to result in high power conversion efficiencies (PCEs). From above analysis, it was found that the polymer/IDIC interfaces should display better performance in the utility of bulk-heterojunction solar cells (BHJ OSC) than polymer/IDTBR interfaces.

Perovskite Solar Cells: Efficient Perovskite Solar Cells over a Broad Temperature Window: The Role of the Charge Carrier Extraction (Adv. Energy Mater. 22/2017)

In article number 1701305, Maria Antonietta Loi and co-workers show that the electron transport capability of the electron-extracting layer dominates the temperature dependence of the performance of hybrid perovskite solar cells. The authors further demonstrate efficient hybrid perovskite solar cells over a temperature range from 295 K to 160 K by n-doping the PCBM electron-extracting layer or using a fullerene derivative with intrinsically higher electron transport capability.