Search

Graphene-based 2D materials have shown extraordinary promise in electrochemical energy storage, owing to their high electrochemical activity, fast carrier mobility, and large electronic conductivity. However, low specific capacity ( 5 mAh cm−2). The highly interpenetrating graphene oxide network in the HAGO/Co@CN electrode accelerates electronic transport. In addition, benefiting from the advanced layered architecture, the HAGO/Co@CN electrode exhibits excellent structural stability and thickness-independent electrochemical performances. By systematically adjusting the orientation of GO/Co@CN nanosheets inside electrode to optimize the electron/ion transmission to deliver high areal capacity and high-rate capability at high mass loading. More importantly, a designed full cell with NCM622 cathode and HAGO/Co@CN anode shows ultrahigh capacity retention of >98% at 1 C after 500 cycles with a commercial-level reversible capacity of 2.3 mAh cm−2.

Understanding the structure–property relationships in antiaromatic molecules is crucial for controlling their electronic properties and designing new organic optoelectronic materials. Here we report the design, synthesis, and characterization of three new antiaromatic molecules (Pn, n = 1–4) based on the pentalene (P) antiaromatic core, to investigate how electron-donating and electron-accepting substituents affect P1–P4 properties. As expected, the optical, HOMO and LUMO energy levels and electronic structure are greatly modulated by core substitution. Compared to the unsubstituted compound (P1), P3 and P4 containing strong electron-withdrawing units reduced antiaromaticity as assessed by nucleus-independent chemical shift (NICS) calculations compared with P2, which is functionalized with strong electron-donating units, showing that substitution strongly tunes local antiaromaticity. Organic field-effect transistors (OFETs) fabricated using these materials indicate that P2 has an average hole mobility of ∼10−4 cm2 V−1 s−1 while P3 has an average electron mobility of up to 0.03 cm2 V−1 s−1, versus FET-inactive P1. Therefore, introduction of strong π-extended electron-withdrawing or electron-donating substituents onto an antiaromatic core is an effective strategy to switch-on charge transport capacity.

Two conjugated polymers (CPs) Fu-F and Fu-Cl that are soluble in a green solvent anisole were successfully synthesized via direct arylation polycondensation (DArP) using a furan-flanked diketopyrrolopyrrole (DPP) derivative (FDPP-Br) as the C–Br monomer and (E)-1,2-bis(3,4-difluorothien-2-yl)ethene (4FTVT) or (E)-1,2-bis(3,4-dichlorothien-2-yl)ethene (4ClTVT) as the C–H monomer. With anisole as the processing solvent and polyethylenimine ethoxylated (PEIE) as the electrode modification layer, n-type organic thin-film transistors (OTFTs) of the polymers were fabricated via bar-coating. The electron mobility (μe) of the devices based on Fu-Cl was only in the magnitude of 10−2 cm2 V−1 s−1, owing to the unfavoured fine granular film morphology. In contrast, Fu-F films showed fibre-like morphology with the polymer chains aligned along the bar-coating direction, which is favourable for the charge transport in OTFTs. Therefore, Fu-F delivered much better device performance with the μe of up to 2.79 cm2 V−1 s−1. Our study demonstrates that green solvent processed high mobility CPs can be synthesized by DArP, an emerging eco-friendly protocol for the synthesis of CPs.

This paper distinguished hydrogen roles to improve electron mobility and carrier concentration in ZnO and Al doped ZnO sputtered films. By combining experimental evidences and theoretical results, we find out that hydrogen located at oxygen vacancy sites (HO) is the main factor gives rise to increase simultaneously mobility and carrier concentration which has not been mentioned before. Introducing appropriate hydrogen content during sputtering not only results in crystalline relaxation but also supports doping Al into ZnO, increasing carrier concentration and electron mobility in the film. First principles calculations confirmed hydrogen substitutional stability for oxygen vacancy, significantly reducing electron conductivity effective mass and hence increasing electron mobility. In particular, 0.8% hydrogen partial pressure ratio achieved 61 cm2V−1s−1 maximum electron mobility, optical transmittance above 82% in visible and near-infrared regions, and 2 × 1020 cm−3 carrier concentrations for H Al co-doped ZnO film. These values approach ideal electrical and optical properties for transparent conducting oxide films. The presence of one maximum electron mobility was attributed to competition between increasing mobility due to restoring effective electron mass and hydrogen passivation of native defects, and decreased electron mobility due to electron-phonon scattering.

Rational functionalization plays an important role to push forward graphene applications in multifarious cutting-edge technologies. A key topic that how to program the regular distribution of functional groups, however, remains a big challenge. Herein, we developed a very simple, high-throughput graphite reduction methodology to attain the negatively-charged graphene which carried ultrahigh-density and evenly-distributed negative charges. Guided by these negative charges, electrophiles were regularly attached to graphene sheets. On the other hand, potassium reduction will not break the carbon-carbon σ-bonds, hence graphene hexagonal lattice was kept as perfect as the pristine pattern. Structural advantages of the negatively-charged graphene derivatives allowed a far more excellent conductivity and electron mobility than the counterparts derived from the prevalent graphene oxide precursor.

Through the introduction of two perylene diimide (PDI) moieties to the triphenylamine (TPA) core, a PDI dimer-based electron transport material has been synthesized with an A (electron acceptor)–D (electron donor)–A structure. It demonstrated a high electron mobility of 8.23 × 10−4 cm2 V−1 s−1 as a thin film and achieved a PCE of 20.07% in perovskite solar cells, higher than that of PC61BM (18.38%) as the standard reference under the same conditions. This is the highest conversion efficiency among various PDI derivatives as ETMs, providing the optimized molecular configuration by combination of twisted core (TPA) and planar peripheral moieties (PDI), as well as matched electronic properties with multiple charge transfer processes.

Compared to epitaxial gallium arsenide (GaAs) grown at regular temperature, low-temperature epitaxial growth of GaAs results in a dramatically shorter carrier lifetime. This produces subpicosecond device responses and enables ultra-high-speed photodetection. However, low-temperature-grown GaAs (LT-GaAs) photodetectors usually exhibit poor responsivity due to the lower carrier mobility in LT-GaAs. Here, the properties and characteristics of the low-temperature-grown material are investigated. Carrier lifetime as a function of growth and annealing temperatures are explored as well as nonlinear optical characteristics and optical absorption well below the bandgap energy of GaAs. Several photodetector styles (photoconductive, PIN, MSM, and waveguide photodetectors) utilizing LT-GaAs are presented. These photodetectors enable a variety of high-speed photonic systems. Their technology and the future use of LT-GaAs are explored, especially in the field of THz emitters and receivers.

A facile solution process to synthesis ZnO thin films was successfully conducted in this work. Zinc acetate dihydrates were used as the main precursor, dissolved in the mixture of acetylacetone and ethanol whichact as solvent and precursor simultaneously. This mixture deposited by spin coating and dried under ambient atmosphere at room temperature. The reaction mechanism, structure, morphology, chemical composition and optoelectrical properties of the resulted ZnO thin film were studied. The as deposited films were annealed at 500 °C for 2 h under O2 gas flow added with H2O vapor and CO2 gas. The ZnO thin films showed a dense, homogenous morphology and high transparency. The film is an n-type semiconductor with 3.18 eV bandgap, has 1.25 × 10−19 cm3 carrier concentration, 12 cm2/Vs electron mobility and 2.42 × 10−3 Ω·cm resistivity making it suitable for application as window layer in a photovoltaic cell.

Nowadays, high-quality metal oxide thin film transistors grown by solution process have the most potential to replace the traditional a-Si TFT as the next generation of transparent electronics for various applications. However, the low intrinsic carrier concentration and poor charge carrier mobility of metal oxide thin film hinder its development. In order to solve these problems, the heterojunction structure was proposed. In this study, the Indium Oxide/Indium Gallium Oxide (In2O3/IGO) heterojunction was systematically investigated, and the existence of a two-dimensional electron gas was found. There is a large accumulation of carriers at the In2O3/IGO heterojunction interface, and the Hall tests show that the In2O3/IGO heterojunction has the highest carrier concentration of 7.82 × 1012 cm−2 and a carrier mobility of 10.22 cm2V−1s−1. This research can provide a theoretical guidance for promoting the development of oxide thin film transistor technology.

The role of hole transport material (HTM) layer is critical to obtain high performances for perovskite solar cells (PSCs). The development of novel HTMs with good stability, low cost, and high hole mobility for PSCs is an essential research direction. Herein, new isoindigo-based HTMs were designed and investigated using density functional theory (DFT) computations combined with Einstein relation and Marcus theory. It was found that the energies of HOMO and LUMO levels were increased with an enhancement in the electron-donating character of substituents located on the diphenylamine moieties. The molecules with X = N(Me)2, NHMe, NH2, OMe, OH, and Me substituents exhibited appropriate energy level alignments with respect to MAPbI3, which indicated the hole could be injected from the MAPbI3 to the designed HTMs. Based on the solvation energies, the designed HTMs would be expected to be soluble in the dichloromethane solvent. The results of the absolute hardness and electrostatic surface potential calculations revealed that the stability of such HTMs was decreased with an increase in the electron-donating character of the substituents positioned onto the diphenylamine groups. All of the designed HTMs, except for the X = OH molecule, illustrated considerably greater hole mobility than that of the Spiro-OMeTAD. In view of the matched HOMO level, good hole mobility, plus acceptable solubility and stability, the designed isoindigo based HTMs would have the potential for replacing the Spiro-OMeTAD in PSCs.

In this article, the electrical properties of nMOSFET devices with different high-k Al₂O₃ capping layer thickness and TiN electrode have been systematically studied at deep cryogenic temperatures ranging from 10 to 300 K. The threshold voltage $V_{TH}$ , transconductance $g_{m}$ , carrier mobility μ, mobility attenuation factor θ , and subthreshold swing (SS) are extracted using the $I_{DS}$ - $V_{GS}$ curves and Y-function method at different temperatures. It is indicated that: 1) all the electrical parameters ( $V_{TH}$ , $g_{m}$ , μ, θ , and SS) show strong temperature dependence in the range of studied temperatures and 2) temperature-dependent electrical properties of nMOSFET devices will modulate at various cryogenic temperatures ascribed to the presence of the Al₂O₃ capping layer on the SiO₂ dielectric layer, which increases the oxide trap density and consequentially adjusts the threshold voltage and mobility of the devices.

The effects of the substituent in p-substituent-benzylidenemalononitrile small molecules have been investigated. We found that the replacement of cyano group in the molecule (M1) by a nitro group (M2) reduces the optical and the electrochemical band gap value which is correlated with a red shift in the absorption and photoluminescence spectra. The insertion of both molecules in P3HT and PCDTBT polymers showed that the quenching parameter efficiency increase from 42 to 71% and from 51 to 64%, respectively. We conclude that M2 is an efficient quencher in P3HT. Electrical measurements in dark showed a diode behaviour for all devices. The effective hole mobility μeff was calculated and shows an enhancement in the case of ITO/P3HT:M2/Al. The calculated values are comparable to those in the literature.

To improve the electron mobility of quantum well (QW) gallium nitride (GaN) high electron mobility transistors (HEMT), we investigated QW and conventional AlGaN/GaN heterostructures grown by metal organic vapor phase epitaxy. Using calculation and experimental results, we revealed that the primary reason for the reduced electron mobility of the QW GaN-HEMT is the increase in intrasubband scattering events because of excessive electron confinement, which is caused by a strong polarization electric field. A strained Al0.30Ga0.70N/Al0.86Ga0.14N buffer structure was applied to alleviate the electric field in the GaN channel while maintaining a strong electron confinement. It enables to increase the piezo polarization of Al0.30Ga0.70N and thus, reduces that of the GaN channel. Consequently, the electron mobility improved to 1420 cm2/Vs for the QW GaN-HEMT structure with the Al0.30Ga0.70N/Al0.86Ga0.14N buffer from 1100 cm2/Vs for the common QW GaN-HEMT structure. To the best of our knowledge, 1420 cm2/Vs at a two-dimensional electron gas density of $1.5\times 10^{{13}}$ cm−2 is the highest electron mobility in the QW double heterostructure.

The discovery and development of ultra-wide bandgap (UWBG) semiconductors is crucial to accelerate the adoption of renewable power sources. This necessitates an UWBG semiconductor that exhibits robust doping with high carrier mobility over a wide range of carrier concentrations. Here we demonstrate that epitaxial thin films of the perovskite oxide NdxSr1−xSnO3 (SSO) do exactly this. Nd is used as a donor to successfully modulate the carrier concentration over nearly two orders of magnitude, from 3.7 × 1018 cm−3 to 2.0 × 1020 cm−3. Despite being grown on lattice-mismatched substrates and thus having relatively high structural disorder, SSO films exhibited the highest room-temperature mobility, ~70 cm2 V−1 s−1, among all known UWBG semiconductors in the range of carrier concentrations studied. The phonon-limited mobility is calculated from first principles and supplemented with a model to treat ionized impurity and Kondo scattering. This produces excellent agreement with experiment over a wide range of temperatures and carrier concentrations, and predicts the room-temperature phonon-limited mobility to be 76–99 cm2 V−1 s−1 depending on carrier concentration. This work establishes a perovskite oxide as an emerging UWBG semiconductor candidate with potential for applications in power electronics.

When designing organic semiconductors, side-chain engineering is as important as modifying the conjugated backbone, which has a significant impact on molecular ordering, morphology, and thus electronic device performance. We have developed three dicyanovinyl-end-capped donor-acceptor diketopyrrolopyrrole-based n-type small molecules (C2C9CN, SiC4CN, and EH4PCN) bearing an identical length of alkyl spacer yet different end-functionalized side chains (i.e., alkyl-, siloxane-, and phosphonate-end pendants). The effects of the end-functionalized side chains on the intrinsic molecular properties, microstructure, and charge transport of the small-molecule series were investigated. In comparison with the alkyl-end side chains, incorporating siloxane-end side chains into the backbone facilitates 2D edge-on oriented high intergrain connectivity/crystallinity and compatibility with the substrate surface, whereas the phosphonate-end analogues have an adverse effect on the film-forming quality due to high polarity. Thereby, an organic field-effect transistor fabricated by SiC4CN shows the best electron mobility up to 1.59 × 10-1 cm2 V-1 s-1 along with a high current on/off ratio >105. This study contributes to our understanding of the role of the end-functionalized side chains (e.g., the effects of polarity and bulkiness of the end groups) for the development of high-performance semiconductors.

Doped graphene could be of use in next-generation electronic and photonic devices. However, chemical doping cannot be precisely controlled in the material and leads to external disorder that diminishes carrier mobility and conductivity. Here we show that graphene can be efficiently doped using a monolayer of tungsten oxyselenide (TOS) that is created by oxidizing a monolayer of tungsten diselenide. When the TOS monolayer is in direct contact with graphene, a room-temperature mobility of 2,000 cm2 V−1 s−1 at a hole density of 3 × 1013 cm−2 is achieved. Hole density and mobility can also be controlled by inserting tungsten diselenide interlayers between TOS and graphene, where increasing the layers reduces the disorder. With four layers, a mobility value of around 24,000 cm2 V−1 s−1 is observed, approaching the limit set by acoustic phonon scattering, resulting in a sheet resistance below 50 Ω sq−1. To illustrate the potential of our approach, we show that TOS-doped graphene can be used as a transparent conductor in a near-infrared (1,550 nm) silicon nitride photonic waveguide and ring resonator. A monolayer of tungsten oxyselenide, created by oxidizing a layer of tungsten diselenide, can be used to efficiently dope graphene, leading to a room-temperature mobility of 2,000 cm2 V–1 s–1 at a hole density of 3 × 1013 cm–2.

Crystalline covalent organic frameworks (COFs) are porous polymeric semiconductors with network topologies, which are built from the integration of selected organic blocks with covalent bond linkages. They have shown great promise for artificial photosynthesis, owing to broad light harvesting, high crystallinity, and high carrier mobility. This Minireview introduces state-of-the-art COF photocatalysts based on different linkages and discusses the origin of photocatalytic activities for hydrogen evolution. Three typical COF photocatalysts, with linkages including imine (-C=N-), β-ketoenamine (O=C-C=C-NH-), and vinylene (-C=C-), are discussed with a particular focus on the advancements in synthetic methodologies and structural design, as well as photoelectronic properties that are relevant to photocatalytic performance. The Minireview is expected to elucidate their structure-property relationships and the way to design photoactive COFs with enhanced performances.

The practical applications of perovskite solar cells (PSCs) are limited by further improvement of their stability and performance. Additive engineering and interface engineering are promising medicine to cure this stubborn disease. Herein, an alkali metal fluoride as an additive is introduced into the tin oxide (SnO2) electron transport layer (ETL). The formation of coordination bonds of F- ions with the oxygen vacancy of Sn4+ ions decreases the trap-state density and improves the electron mobility; the hydrogen bond interaction between the F ion and amine group (FA+) of perovskite inhibits the diffusion of organic cations and promotes perovskite (PVK) stability. Meanwhile, the alkali metal ions (K+, Rb+, and Cs+) permeated into PVK fill the organic cation vacancies and ameliorate the crystal quality of PVK films. Consequently, a SnO2-based planar PSC exhibits a power conversion efficiency (PCE) of 20.24%, while the PSC modified by CsF achieves a PCE of 22.51%, accompanied by effective enhancement of stability and negligible hysteresis. The research results provide a typical example for low-cost and multifunctional additives in high-performance PSCs.

Layered metal chalcogenides with highly promising thermoelectric properties have attracted attention owing to their intrinsically low thermal conductivity, which originates from their unique layered structure and van der Waals bonding. InSe, a post-transition metal chalcogenide, also has layered atomic structure and low thermal conductivity. We investigate the effects of S doping of Si-doped InSe, In0.9Si0.1Se. The S-doped In0.9Si0.1Se exhibits enhanced thermoelectric properties, with a higher power factor and lower thermal conductivity compared to Si-doped InSe. A significant increase in carrier mobility has an overall positive effect on the electronic transport properties, resulting in a systematic increase in power factor from 0.05 to 0.15 mW/mK2 with S doping. In addition, the thermal conductivity systematically decreases with S doping owing to additional point-defect scattering. Because of the higher power factor and lower thermal conductivity, the thermoelectric figure of merit of the In0.9Si0.1Se0.9S0.1 sample at 735 K was 0.18, which is 3.6 times that of In0.9Si0.1Se.

TiN films with different thicknesses (17.9–102.8 nm) were prepared using rf magnetron sputtering to study the effect thickness on the plasmonic, electrical, and optical properties. X-ray diffraction revealed the amorphous-like structure for thinner films with thicknesses lower than 50.3 nm, whereas polycrystalline of face-centered cubic TiN structure was observed for thicker films. Scanning electron microscopy observations revealed rounded nano-crystallites morphology for TiN films. The EDAX depicted oxygen in the TiN films which attributed to the residual oxygen inside the sputtering chamber and to the partial surface oxidation resulted from the exposure to atmospheric air. As the thickness increased from 17.9 to 102.8 nm, the carrier concentration increases from 1.47 × 1022 to 3.51 × 1022 cm−3 and the carrier mobility increased from 0.091 to 0.489 cm2/V.s, which resulted in a resistivity decrease from 4.65 × 10–3 to 3.64 × 10–4 Ω cm. Two absorption bands around 250 and 1000 nm were observed. The band around 1000 nm was ascribed to the localized surface plasmon resonance (LSPR) and increased with increasing the film thickness. The optical band gap and refractive index values decreased monotonically with increasing the film thickness. It is also inferred that the thickness has a strong influence on the values of real and imaginary parts of the dielectric function. Applying various figures of merit indicated that the prepared TiN films are probably not practical for LSPR device fabrication however they are probably suitable for practical transformation optics and superlens device applications.

Covalent organic frameworks (COFs) with efficient charge transport and exceptional chemical stability are emerging as an import class of semiconducting materials for opto-/electronic devices and energy-related applications. However, the limited synthetic chemistry to access such materials and the lack of mechanistic understanding of carrier mobility greatly hinder their practical applications. Herein, we report the synthesis of three chemically stable polyarylether-based metallophthalocyanine COFs (PAE-PcM, M = Cu, Ni, and Co) and facile in situ growth of their thin films on various substrates (i.e., SiO2/Si, ITO, quartz) under solvothermal conditions. We show that PAE-PcM COFs thin films with van der Waals layered structures exhibit p-type semiconducting properties with the intrinsic mobility up to ∼19.4 cm2 V-1 s-1 and 4 orders of magnitude of increase in conductivity for PAE-PcCu film (0.2 S m-1) after iodine doping. Density functional theory calculations reveal that the carrier transport in the framework is anisotropic, with the out-of-plane hole transport along columnar stacked phthalocyanine more favorable. Furthermore, PAE-PcCo shows the redox behavior maximumly contributes ∼88.5% of its capacitance performance, giving rise to a high surface area normalized capacitance of ∼19 μF cm-2. Overall, this work not only offers fundamental understandings of electronic properties of polyarylether-based 2D COFs but also paves the way for their energy-related applications.

Perovskite-perovskite tandem solar cells have bright prospects to improve the power conversion efficiency (PCE) beyond the Shockley-Queisser (SQ) limit of single-junction solar cells. The star lead-based halide perovskites are well-recognized as suitable candidates for the front cell, thanks to their suitable band gap (∼1.8 eV), strong optical absorption, and high certified PCE. However, the toxicity of lead for the front cell and the lack of a narrow band gap (∼1.1 eV) for the rear cell seriously restrict the development of the two-junction tandem cell. To break through this bottleneck, a novel Dion-Jacobson (DJ)-type (n = 2) chalcogenide perovskite CsLaM2X7 (M = Ta, Nb; X = S, Se) has been found based on the powerful first-principles and advanced many-body perturbation GW calculations. Their excellent electronic, transport, and optical properties can be summarized as follows. (1) They are stable and environmentally friendly lead-free materials. (2) The direct band gap of CsLaTa2Se7 (0.96-1.10 eV) is much smaller than those of lead-based halide perovskites and very suitable for the rear cell in the two-junction tandem cell. (3) The carrier mobility in CsLaTa2Se7 reaches 1.6 × 103 cm2 V-1 s-1 at room temperature. (4) The absorption coefficients (3-5 × 105 cm-1) are 1 order higher than that of Si (104 cm-1). (5) The estimated PCEs of the Cs2Sb2Br8-CsLaTa2Se7 tandem cell (33.3%) and the concentrator solar cell (35.8% in 100 suns) are higher than those of the best recorded GaAs-Si tandem cell (32.8%) and the perovskite-perovskite tandem solar cell (24.8%). These energetic results strongly demonstrate that the novel lead-free chalcogenide perovskites CsLaM2X7 are good candidates for the rear cell of tandem cells.

The development of n-type organic electrochemical transistors (OECTs) lags far behind their p-type counterparts. In order to address this dilemma, we report here two new fused bithiophene imide dimer (f-BTI2)-based n-type polymers with a branched methyl end-capped glycol side chain, which exhibit good solubility, low-lying LUMO energy levels, favorable polymer chain orientation, and efficient ion transport property, thus yielding a remarkable OECT electron mobility (μe ) of up to ≈10-2 cm2 V-1 s-1 and volumetric capacitance (C*) as high as 443 F cm-3 , simultaneously. As a result, the f-BTI2TEG-FT-based OECTs deliver a record-high maximum geometry-normalized transconductance of 4.60 S cm-1 and a maximum μC* product of 15.2 F cm-1 V-1 s-1 . The μC* figure of merit is more than one order of magnitude higher than that of the state-of-the-art n-type OECTs. The emergence of f-BTI2TEG-FT brings a new paradigm for developing high-performance n-type polymers for low-power OECT applications.

In this work, we synthesized and characterized two quinoidal small molecules based on benzothiophene modified and original isatin terminal units, benzothiophene quinoidal thiophene (BzTQuT) and quinoidal thiophene (QuT), respectively, to investigate the effect of introducing a fused ring into the termini of quinoidal molecules. Extending the terminal unit of the quinoidal molecule affected the extension of π-electron delocalization and decreased the bond length alternation, which led to the downshifting of the collective Raman band and dramatically lowering the band gap. Organic field-effect transistor (OFET) devices in neat BzTQuT films showed p-type transport behavior with low hole mobility, which was ascribed to the unsuitable film morphology for charge transport. By blending with an amorphous insulating polymer, polystyrene, and poly(2-vinylnaphthalene), an OFET based on a BzTQuT film annealed at 150 °C exhibited improved mobility up to 0.09 cm2 V–1 s–1. This work successfully demonstrated that the extension of terminal groups into the quinoidal structure should be an effective strategy for constructing narrow band gap and high charge transporting organic semiconductors.

This research presents the effect of different concentrations of iron (Fe) as dopants on the physical properties of the copper selenide (Cu3Se2) nanoparticle (NPs). The physical properties of the Cu3Se2 NPs were investigated using structural, morphological, and optical analysis. The results revealed that the Fe concentrations change the crystallite size (from ∼8 to 44 nm) and strain (from ∼0.0007 to 0.0030). Fe-doped Cu3Se2 NPs showed a higher optical energy band gap in comparison to the un-doped sample (1.80 eV). The films prepared by green binder (ethyl cellulose) indicated that the sample with minimum Fe concentration presents the highest carrier concentration (9.56e+18 cm−3) and lowest ideality factor (2.02) amounts. The electrical study shows space charge limited current (SCLC) mechanism in Fe-doped Cu3Se2 NPs that is not observed in un-doped sample. Using this mechanism, the highest carrier mobility (16.22 cm+2V−1s−1) obtained for sample with the lowest amount of Fe concentrations.

InGaAs is a potential candidate for a next-generation channel material of complementary metal-oxide-semiconductor devices based on its excellent electron mobility. In this study, the surface behaviors of the InGaAs after treatments in H3PO4/H2O2/H2O and HNO3/H2O2/H2O mixtures were investigated and compared with that after treatment in a HCl/H2O2/H2O mixture. Although the presence of Cl− in an acidic solution suppressed the overall etching reaction and material loss of the InGaAs surface, Cl− induced the roughening of the InGaAs surface. The smallest InGaAs/Al2O3 interface charge trap density was observed when the InGaAs surface was prepared in the H3PO4/H2O2/H2O solution. It was also confirmed that the H3PO4/H2O2/H2O-treated InGaAs surface had the highest electron mobility among the samples and the lowest interfacial defect density, such as arsenic vacancies and antisites. Finally, it was concluded that surface preparation of InGaAs with H3PO4/H2O2/H2O effectively improved the interfacial electrical properties at the metal-oxide-InGaAs semiconductor by successfully minimizing surface roughening and the interfacial defect density compared to a well-known HCl/H2O2/H2O solution process.

Graphene is influenced by its surrounding environment, such as adsorbates, charged impurities, and interface traps, owing to its large surface area and ultra-thin thickness. Herein, the effect of substrate conditions on the doping and degradation of graphene is investigated. The hydroxyl (-OH) groups on the silicon dioxide (SiO2) substrate formed by oxygen plasma treatment altered the characteristics of the overlying graphene. On exposure to ultraviolet (UV) light, the p-doping level of graphene on oxygen-plasma-treated SiO2 (P-SiO2) increased and degradation occurred, while graphene on bare SiO2 showed no change. The graphene on P-SiO2 had higher reactivity due to doping induced by –OH groups on the SiO2 surface. The graphene field-effect transistors (G-FETs) on the P-SiO2 also showed the reduced carrier mobility and larger shift of charge neutral point. However, during UV exposure, the device showed sever degradation in electrical conductivity and failure after 60 min. Meanwhile, the device on the bare SiO2 showed negligible changes even after UV exposure. Our results unveil the origin of degradation in the graphene and show a way to prevent the unwanted changes or degradation of graphene, which is highly important for the practical application of graphene.

Hole transporting materials (HTMs) play an unparalleled role in heightening the stability and photovoltaic performance of perovskite solar cells (PSCs). The organic small molecule spiro-OMeTAD is frequently utilized for HTM in PSCs. However, the raw spiro-OMeTAD without dopant would be harmful to the development of highly efficient PSCs, due to its unsatisfied hole mobility and conductivity. Therefore, we introduce an inorganic dopant (chromium trioxide, CrO3) into the lithium-salt doped spiro-OMeTAD. Because of the exclamatory oxidizability of CrO3, it can accelerate the oxidation of spiro-OMeTAD and thereby enhancing the hole mobility of HTM. The introduction of CrO3 not only substantially decreases the density of defects, but also adjusts spiro-OMeTAD energy band, and thus effectively suppresses the hysteresis and improving stability of PSCs. In the end, we obtained a power conversion efficiency (PCE) as high as 22.6% after doping CrO3 in spiro-OMeTAD. The facile, low cost and outstanding photovoltaic performance render CrO3 an excellent dopant for HTMs in PSCs.

Herein, we report a detailed study on creating heterojunction between graphitic carbon nitride (g-C3N4) and bismuth phosphate (BiPO4), enhancing the unpaired free electron mobility. This leads to an accelerated photocatalysis of 2,4-dichlorophenols (2,4-DCPs) under sunlight irradiation. The heterojunction formation was efficaciously conducted via a modest thermal deposition technique. The function of g-C3N4 plays a significant role in generating free electrons under sunlight irradiation. Together, the generated electrons at the g-C3N4 conduction band (CB) are transferred and trapped by the BiPO4 to form active superoxide anion radicals (•O2-). These active radicals will be accountable for the photodegradation of 2,4-DCPs. The synthesized composite characteristics were methodically examined through several chemical and physical studies. Due to the inimitable features of both g-C3N4 and BiPO4, its heterojunction formation, 2.5wt% BiPO4/g-C3N4 achieved complete 2,4-DCP removal (100%) in 90 min under sunlight irradiation. This is due to the presence of g-C3N4 that enhanced electron mobility through the formation of heterojunctions that lengthens the electron-hole pairs' lifetime and maximizes the entire solar spectrum absorption to generate active electrons at the g-C3N4 conduction band. Thus, this formation significantly draws the attention for future environmental remediation, especially in enhancing the entire solar spectrum's harvesting.

Reduced graphene oxide (rGO) is among only a few p-type transparent conductors. This article describes the use of pre-decoration of gold nanoparticles (AuNPs) to tune the optoelectronic properties of rGO film. High-purity Au is sputtered on GO film before the thermal reduction process at 825°C in a H2/CH4 environment. For the optimum 30 s Au sputtering, a high-temperature process transformed the Au nanoballs into nanowires. These conditions resulted in the maximum hole mobility of 158.99 cm2 V−1 s−1 and the minimum sheet resistance of 325.82 Ω□−1. The degree of reduction for the rGO-Au(30s) sample was the highest, since it had the lowest optical transmittance of 0.871 and the lowest bandgap of 3.75 eV. It thus represents the best p-type transparent conductor, with a figure of merit σdc/σop of approximately 8.11. The deconvoluted Raman fit elaborates more on the elimination of defect components on the rGO samples. The integrated area ratio for several defect peaks over a pristine peak was the lowest for the rGO-Au(30s), at 3.98. The AuNPs intervened in the reduction process by repairing the lattice defects for the in-plane carbon sp2, edge, amorphous phase, and out-of-plane sp2–sp3. This was responsible for the great improvement in the carrier transport mechanism and the value of σdc/σop.

In this work, the thermoelectric performance of a typical small-molecule organic semiconductor rubrene under different hydrostatic pressures was studied by first-principles calculation and molecular dynamics simulation. The ZT value of rubrene can reach 1.6 at 400 K due to an unprecedented increase in hole mobility under hydrostatic pressure. The underlying mechanism is ascribed to the suppression of low-frequency phonons (which weakens electron-phonon scattering) and the increase in the intermolecular electronic coupling. The effect of uniaxial stress has also been investigated to confirm this conclusion. Our results provide meaningful insights to understand the relationship between thermoelectric properties and hydrostatic pressure in organic semiconductors.

Previous studies have shown influence of aliphatic side chain length and type on the transport properties of naphthalenediimide (NDI) materials by affecting molecular arrangement. There is lack of comparative study on the presence or absence of unsaturation in side chain and its effect on optical and electronic properties of NDI. The present work focuses on the structure–property relationship of four NDI derivatives bearing octyl (C8, OctA-NDI), hexadecyl (C16, HD-NDI), octadecyl (C18, ODA-NDI) and oleyl (C18-un, unsaturated, OLA-NDI) chain on imide-nitrogen. The self-assembling behaviour of the molecules is studied in concentrated solutions as fresh and aged samples in four different solvents by absorbance and emission spectroscopy. With increase in alkyl chain length, the aggregation behaviour is observed to increase. Very interestingly introduction of unsaturation in side chain reduces aggregation and restores the monomeric properties. Self-assembled microstructures formation was studied by scanning electron microscopy where all the four materials show different types of self-assembly formation. Finally, we compared the thermally activated electron conductivity and electron mobility of NDI derivatives, where also the side chain structure clearly influences the electron transport. Electron mobility decreases on increasing chain length from C8 to C18 and again increases in C18-un. A rationale for the structure–property relationship has been given based on the molecular packing and intermolecular π–π interactions. This study contributes significantly towards designing new NDI derivatives bearing long side chains with hampered aggregation for niche applications.

Solution-processed metal oxide (MO) thin films have been extensively studied for use in thin-film transistors (TFTs) due to their high optical transparency, simplicity of fabrication methods, and high electron mobility. Here, we report, for the first time, the improvement of the electronic properties of solution-processed indium oxide (InOx) films by the subsequent addition of an organic p-type semiconductor material, here 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), yielding organic-inorganic hybrid TFTs. The addition of TIPS-pentacene not only improves the electron mobility by enhancing the charge carrier percolation pathways but also improves the electronic and temporal stability of the IDS(VG) characteristics as well as reduces the number of required spin-coating steps of the InOx precursor solution. Very interestingly, the introduction of 10 nm TIPS-pentacene films on top of 15 nm InOx layers allows the fabrication of either enhancement- or depletion-mode devices with only minimal changes to the fabrication process. Specifically, we find that when the TIPS-pentacene layer is added on top of the source/drain electrodes, resulting in devices with embedded source/drain electrodes [embedded electrode TFTs (EETFTs)], the devices exhibit an enhancement-mode behavior with an average mobility (μ) of 6.4 cm2 V-1 s-1, a source-drain current ratio (Ion/Ioff) of around 105, and a near-zero threshold voltage (VTH). When on the other hand the TIPS-pentacene layer is added before the source-drain electrodes, i.e., in top-contact electrode TFTs (TCETFTs), a very clear depletion mode behavior is observed with an average μ of 6.3 cm2 V-1 s-1, an Ion/Ioff ratio of over 105, and a VTH of -80.3 V. Furthermore, a logic inverter is fabricated combining the enhancement (EETFTs)- and depletion (TCETFTs)-mode transistors, which shows a potential for the construction of organic-inorganic hybrid electronics and circuits.

We demonstrate the potential of using reduced-fluorinated graphene oxide (F-rGO) in improving the performance of polymer bulk-heterojunction when added as a ternary additive. The best device using poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4–b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-th): [6,6]-phenylC71-butyric-acid-methyl-ester (PC71BM): F-rGO (5 wt%) ternary blend, showed a higher power conversion efficiency (PCE) ~ 7.36 % compared to devices without F-rGO (PCE ~ 3.54 %). F-rGO nanosheets not only enhance the charge dissociation by promoting the electron extraction from PTB7-th to PCBM, but also support charge transport by providing conducting pathways. It is attributed to F-rGO induced p-doping effect owing to high work-function of F-rGO nanosheets, and enhanced hole mobility due to improved film morphology. This results in enhanced performance of (PTB7-th:PCBM:F-rGO) based-ternary organic solar cell devices.

A novel design for a silicon-integrated avalanche photodiode (APD) capable of high internal gain (>16,000) is presented. The APD was fabricated in an unmodified, commercial high-volume, high-performance (300 GHz ${f}_{T}/{f}_{\text {MAX}}$ ) silicon-germanium (SiGe) BiCMOS technology. The APD’s high gain is partially attributed to the enhanced lateral carrier mobility of its strained SiGe anode, and the low sheet resistance of its cathode contact. These design aspects lower parasitic resistance and improve junction electric field uniformity, increasing maximum gain. For applications not requiring maximum device speed, a time-resolved overall responsivity of 4.2 A/W is demonstrated, with a photocurrent pulse fall time (90%/10%) of 46 ns at 1066 nm. Alternatively, for applications requiring faster speed, the device can be biased to 0.16 A/W with a fall time of 2.5 ns, or 0.07 A/W with a fall time of 0.8 ns.

This study presents a p-type doping method for donor–acceptor-type conjugated semiconducting copolymer-based field-effect transistors (FETs) with a fluoropolymer dielectric film. The polymeric FET, which initially comprises a non-polar polymer dielectric layer (poly (methyl methacrylate), PMMA), shows ambipolar behavior owing to the well-balanced electron-accepting and -donating properties of the cyclopentadithiophene (CDT) and pyridyl-2,1,3-thiadiazole (PTz)-based conjugated polymer backbone system. However, when combined with an amorphous fluoropolymer (CYTOP) dielectric layer, the FET device exhibits that their ambipolar behavior remarkably changes to a high-performance p-type FET; the hole mobility enhanced by a factor of ~3 and the threshold voltage significantly shifted from −29 V to −12 V. The density of trap states in the CDT-PTz-based polymeric FETs with a CYTOP dielectric layer, which was estimated from the temperature-dependent transfer characteristics, was narrower and shallower than that of polymeric FETs with a PMMA dielectric layer. As such, it can be inferred that the deep-trap states are filled with additional doped charges from the surface polarization induced by the fluorinated dielectrics at the semiconductor-dielectric interface.

Compared with bulk material-based sensors, functional sensors fabricated with nanomaterials have many advantages, such as high sensitivity, multifunctional integration, low power-dissipation, and low cost. Black phosphorus (BP) is a two-dimensional (2D) crystal material, which has a higher molecular adsorption energy, tunable direct band gap, high carrier mobility, ambipolar characteristics, and high current on/off ratio. In this paper, BP bulk was ground into powder, and then the powder was dispersed in dimethylformamide (DMF) to obtain two-dimensional BP nanosheets solution. Afterwards, the black phosphorus nanosheets and H2PtCl6 solution were mixed to obtain the Pt functionalized BP nanocomposite by one-step reduction method. Pt nanoparticles were dispersed on the surface of BP nanosheets with highly uniform size. The Pt functionalized BP nanocomposite exhibited a high response of 2.19 to 10 ppm NOx in a short period of 1.93 s at room temperature. The detection limit was as low as 30 ppb. The Pt functionalized BP nanocomposite will be useful for precise detection of NOx.

The development of n-type semiconductors lags far behind that of their p-type counterparts, demonstrating the exploration of exclusive n-type π-conjugated polymers is significant. The double B←N-bridged bipyridine (BNBP)-based polymers P-BNBP-TVT containing (E)-1,2-di(thiophen-2-yl)ethene (TVT) previously reported exhibits ambipolar character because of the electron-rich nature. Herein, we incorporated strong electron-withdrawing cyano groups into the 3,3′-positions of the TVT moiety to a copolymer P-BNBP-2CNTVT to develop n-type π-conjugated polymers. The LUMO/HOMO energy levels of P-BNBP-2CNTVT are −3.80/−5.95 eV, respectively, which are ~0.4 eV lower than that of P-BNBP-TVT without cyano groups. Unsurprisingly, compared with ambipolar P-BNBP-TVT, the organic field-effect transistors (OFETs) based on P-BNBP-2CNTVT showed unipolar n-type characteristics with an electron mobility of 0.026 cm2 · V−1 · s−1 and a lower threshold voltage of ~25 V as well as high I on/I off of ~105. This study demonstrates that organoboron π-conjugated polymers could be regarded as a tool for constructing exclusive n-type semiconducting polymers used in OFETs.

Abstract We provide a comparative study of basic electrical properties of bulk single crystals of transparent semiconducting oxides (TSOs) obtained directly from the melt (9 compounds) and from the gas phase (1 compound), including binary (β-Ga2O3, In2O3, ZnO, SnO2), ternary (ZnSnO3, BaSnO3, MgGa2O4, ZnGa2O4), and quaternary (Zn1−xMgxGa2O4, InGaZnO4) systems. Experimental outcome, covering over 200 samples measured at room temperature, revealed n-type conductivity of all TSOs with free electron concentrations (ne) between 5 × 1015 and 5 × 1020 cm−3 and Hall electron mobilities (μH) up to 240 cm2 V−1 s−1. The widest range of ne values was achieved for β-Ga2O3 and In2O3. The most electrically conducting bulk crystals are InGaZnO4 and ZnSnO3 with ne > 1020 cm−3 and μH > 100 cm2 V−1 s−1. The highest μH values > 200 cm2 V−1 s−1 were measured for SnO2, followed by BaSnO3 and In2O3 single crystals. In2O3, ZnO, ZnSnO3, and InGaZnO4 crystals were always conducting, while others could be turned into electrical insulators. Graphic abstract

The performance of photocatalytic fuel cell (PFC) is mainly determined by photoanode. In order to reduce the recombination rate of electron–hole pairs and extend the light response wavelength, g-C3N4/WO3/TiO2/Ti photoanode was successfully fabricated by mixed sol–gel dipping method. Its maximum photocurrent density is 2.27 mA·cm−2 at 1.1 V (vs. SCE), which is 1.64 and 1.57 times that of WO3/TiO2/Ti and g-C3N4/TiO2/Ti, respectively. The maximum power density, short circuit current density, and RhB degradation efficiency of PFC with g-C3N4/WO3/TiO2/Ti-Cu photoanode and Cu cathode are 19.35 μW·cm−2, 0.20 mA·cm−2, and 87.7%, respectively. The excellent performance of PFC is mainly attributed to the fact that TiO2/Ti is co-doped with g-C3N4 and WO3, which greatly expands its light absorption range, strengthen its light absorption intensity, and improves its carrier mobility.

Copper(I) thiocyanate (CuSCN) is a stable, low-cost, solution-processable p-type inorganic semiconductor used in numerous optoelectronic applications. Here, for the first time, we employ the time-of-flight (ToF) technique to measure the out-of-plane hole mobility of CuSCN films, enabled by the deposition of 4 μm-thick films using aerosol-assisted chemical vapor deposition (AACVD). A hole mobility of ∼10–3 cm2/V s was measured with a weak electric field dependence of 0.005 cm/V1/2. Additionally, by measuring several 1.5 μm CuSCN films, we show that the mobility is independent of thickness. To further validate the suitability of our AACVD-prepared 1.5 μm-thick CuSCN film in device applications, we demonstrate its incorporation as a hole transport layer (HTL) in methylammonium lead iodide (MAPbI3) perovskite solar cells (PSCs). Our AACVD films result in devices with measured power conversion efficiencies of 10.4%, which compares favorably with devices prepared using spin-coated CuSCN HTLs (12.6%), despite the AACVD HTLs being an order of magnitude thicker than their spin-coated analogues. Improved reproducibility and decreased hysteresis were observed, owing to a combination of excellent film quality, high charge-carrier mobility, and favorable interface energetics. In addition to providing a fundamental insight into charge-carrier mobility in CuSCN, our work highlights the AACVD methodology as a scalable, versatile tool suitable for film deposition for use in optoelectronic devices.

In comparison with the common-used electron donor (D)-electron acceptor (A) type symmetric polymers with regular structures, their asymmetric counterparts have received much less attention and seldom been applied in polymer solar cells. Since the precise modulation of π bridge can significantly influence the photoelectric properties of D-A type polymers, π bridges of tailorable thiophenes are introduced into benzodithiophene (BDT)-benzodithiophene-4,8-dione (BDD) copolymers in both symmetric and asymmetric patterns. Together with the halogen substituent of fluorine or chlorine on BDT, four polymer donors are designed and synthesized. As expected, PTB2T-F and PTB2T-Cl with the asymmetric π bridges of thiophene and hexyl-bithiophene exhibit better planarity, stronger intermolecular interaction and higher hole mobility than P2TB2T-F and P2TB2T-Cl with the symmetric π bridges of hexyl-bithiophene. The more suitable phase separation and optimized nanomorphology is determined by the reasonable miscibility between asymmetric polymer and acceptor, which is evaluated by Flory-Huggins interaction, contributing to the extremely higher performance than that of symmetric counterpart. Moreover, paired with IT-4F as the acceptor, PTB2T-F affords better device performances than the reference BDT-BDD polymer PM6 with the symmetry π bridge of thiophene. These results demonstrate that the precise modulation of asymmetric π bridges is a promising strategy to construct high-efficiency D-A type polymer donors.

A dissymmetric backbone and selenophene substitution on the central core was used for the synthesis of symmetric or dissymmetric A-DA'D-A type non-fullerene small molecular acceptors (NF-SMAs) with different numbers of selenophene. From S-YSS-Cl to A-WSSe-Cl and to S-WSeSe-Cl, a gradually red-shifted absorption and a gradually larger electron mobility and crystallinity in neat thin film was observed. A-WSSe-Cl and S-WSeSe-Cl exhibit stronger and tighter intermolecular π-π stacking interactions, extra S⋅⋅⋅N non-covalent intermolecular interactions from central benzothiadiazole, better ordered 3D interpenetrating charge-transfer networks in comparison with thiophene-based S-YSS-Cl. The dissymmetric A-WSSe-Cl-based device has a PCE of 17.51 %, which is the highest value for selenophene-based NF-SMAs in binary polymer solar cells. The combination of dissymmetric core and precise replacement of selenophene on the central core is effective to improve Jsc and FF without sacrificing Voc .

The formation of n (Znx – Cd1-x)S-PSI neterojunction solar cell under various heat treatments is investigated in order to optimize their behaviour. The results obtained indicate that substantial improvement can be made in the conversion and quantum efficiency of cells witn x about 0.75 , deposited at substrate temperature of 370oc , after annealing in H2/N2 atmosphere at 600oc. Under these conditions , minimum density of interface states good lattice maton , and maximum electron mobility are achieved.

2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-OMeTAD), as the most common used hole transport material (HTM), plays a significant role in the normal structured (n-i-p) high-efficiency perovskite solar cells (PSCs). In general, it is prepared by a halogen solvent (chlorobenzene, CBZ) and needs an ion dopant (lithium bis (trifluoromethanesulfonyl)imide, Li-TFSI) to improve its conductivity and hole mobility. However, such a halogen solvent is not environmentally friendly and the widely used Li-TFSI dopant would affect the stability of PSCs. Herein, we develop a non-halogen solvent—tetrahydrofuran (THF)-prepared spiro-OMeTAD solution with a new p-type dopant, potassium bis(fluorosulfonyl)imide (K-FSI), to apply into PSCs. By this strategy, high-hole-mobility spiro-OMeTAD film is achieved. Meanwhile, the potassium ions introduced by diffusion into perovskite surface passivate the interfacial defects. Therefore, a hysteresis-free champion PSC with an efficiency of 21.02% is obtained, along with significantly improved stability against illumination and ambient conditions. This work provides a new strategy for HTMs toward hysteresis-free high-efficiency and stable PSCs by substituting dopants.

Two-dimensional Ruddlesden–Popper (2DRP) metal halides have attracted extensive attention in photovoltaic applications due to their high stability, low self-doping levels and long-lived free carriers. Among them, (PA)2(MA)2Pb3I10 presents itself as a superior candidate, demonstrating greater moisture resistance and improved heat and light stability over many other 2DRP metal halides. This study takes on the opportunity to search for lead-free alternatives by investigating the optoelectronic and carrier transport properties, as well as the photovoltaic performance of such (PA)2(MA)2M3I10 type metal halides as the photovoltaic absorber, where M = Pb, Cd, Cr, Cu, Ge, Mn, Ni, Sn, Yb, Zn. Our results indicate that the bandgap of (PA)2(MA)2M3I10 can be tuned to the optimum photovoltaic application range of 0.9–1.6 eV, along with improved optical and enhanced photo-response capacity, when Sn, Cd, Mn, Ge, and Zn are used to replace Pb. In particular, (PA)2(MA)2Zn3I10 possesses the largest Stokes shift and Huang-Rhys factor, while showing the best photoluminescence tendency and broadest emission nature. (PA)2(MA)2Ge3I10 displays the most excellent of carrier transport capacities with high mobilities of 73 cm2 V−1 s−1 and 43 cm2 V−1 s−1 for electron and hole carriers, respectively, which are even comparable to that of 3D counterparts. Furthermore, (PA)2(MA)2Zn3I10 is predicted to have the highest power conversion efficiency of 23.36% based on an empirical energy loss (0.5 eV), which is quite close to the Shockley–Queisser limit, thereby featuring it as a suitable absorber for photovoltaic applications. These findings shed light on new strategies for designing and developing lead-free 2DRP metal halides targeted at future applications in photovoltaic solar cell devices.

A comprehensive investigation on the hot-carrier-induced interface state generation and its impact on carrier mobility in nMOSFET is performed. ${I}$ – ${V}$ compact modeling and charge pumping (CP) characterization are used as independent ways to evaluate the interface state density as a function of hot-carrier-induced aging. From the two techniques, similar power-law time exponents of the interface state density kinetics are obtained. Assisted by the quasi-spectroscopic (temperature-resolved) CP measurement, the extracted interface state density is further correlated with the ${I}$ – ${V}$ modeling results: an universal mobility degradation normalization parameter ${N} _{\text {it,ref}} = {\sim }\, {4.1} \times {10}^{{11}}$ /cm2 is reported, irrespective of the effective oxide thickness (EOT), stress temperature, or the relative degradation of the device under test (DUT). Supported by the fundamental principles deployed in the derivation and the broad range of experimental conditions considered for its validation, the reported normalization parameter could serve as a modeling constant in the commonly used ${I}$ – ${V}$ compact models to correlate the mobility degradation with the interface state density induced by hot carrier stress.

Tin dioxide (SnO2) has been demonstrated as one of the promising electron transport layers for high-efficiency perovskite solar cells (PSCs). However, scalable fabrication of SnO2 films with uniform coverage, desirable thickness and a low defect density in perovskite solar modules (PSMs) is still challenging. Here, we report preparation of high-quality large-area SnO2 films by chemical bath deposition (CBD) with the addition of KMnO4. The strong oxidizing nature of KMnO4 promotes the conversion from Sn(II) to Sn(VI), leading to reduced trap defects and a higher carrier mobility of SnO2. In addition, K ions diffuse into the perovskite film resulting in larger grain sizes, passivated grain boundaries, and reduced hysteresis of PSCs. Furthermore, Mn ion doping improves both the crystallinity and the phase stability of the perovskite film. Such a multifunctional interface engineering strategy enabled us to achieve a power conversion efficiency (PCE) of 21.70% with less hysteresis for lab-scale PSCs. Using this method, we also fabricated 5 × 5 and 10 × 10 cm2 PSMs, which showed PCEs of 15.62% and 11.80% (active area PCEs are 17.26% and 13.72%), respectively. For the encapsulated 5 × 5 cm2 PSM, we obtained a T80 operation lifetime (the lifespan during which the solar module PCE drops to 80% of its initial value) exceeding 1000 h in ambient condition.

Sol-gel high-k metal oxide thin film transistors (TFTs) have fascinated huge interest due to their prospective applications in cost-effective, low operating voltage electronics such as sensors, radio frequency identification tags, portable electronics and backplane circuitry for flat panel display. In this work, we report a sol–gel synthesis procedure of γ-phase of lithium aluminates (γ-LiAlO2) which is a high-k material due to the ionic polarization of mobile Li+ of the crystal. This high-k dielectric has been successfully utilized as a gate insulator of a low voltage indium zinc oxide (IZO) TFT. The optimize device shows a moderate on/off ratio of 9 × 102 and electron mobility of 4 cm2 V−1 s−1 under 2.0 V operation. This γ-LiAlO2 dielectric has been synthesized by cost-effective sol–gel technique followed by annealing process at 700 °C.

Layer-by-layer (LBL) sequential solution processing of the active layer has been proven as an effective strategy to improve the performance of organic solar cells (OSCs), which could adjust vertical phase separation and improve device performance. Although perylene diimide (PDI) derivatives are typical acceptors with excellent photoelectric properties, there are few studies on PDI-based LBL OSCs. Herein, three PDI acceptors (TBDPDI-C5, TBDPDI-C11, and SdiPDI) were used to fabricate LBL and bulk heterojunction (BHJ) OSCs, respectively. A series of studies including device optimization, photoluminescence (PL) quenching, dependence of light intensity, carrier mobility, atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing-incidence wide-angle X-ray scattering (GIWAXS), and depth analysis X-ray photoelectron spectroscopy (DXPS) were carried out to make clear the difference of the PDI-based LBL and BHJ OSCs. The results show that LBL OSCs possess better charge transport, higher and more balanced carrier mobility, less exciton recombination loss, more favorable film morphology, and proper vertical component distribution. Therefore, all the three PDI acceptor-based LBL OSCs exhibit higher performance than their BHJ counterparts. Among them, TBDPDI-C5 performs best with a power conversion efficiency of 6.11% for LBL OSCs, higher than its BHJ OSC (5.14%). It is the first time for PDI small molecular acceptors to fabricate high-efficiency OSCs by using an LBL solution-processed method.