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P-poly(9, 9-diethylfluorene)/n-silicon nanowire (SiNW) heterojunctions were prepared by spin coating p-type conductive organic polymer on as-prepared n-SiNWs, which were fabricated by electroless metal deposition method. This hybrid nanowire p-n heterojunction shows good rectifying behavior with turn-on voltage of about 1 V at room temperature. Temperature-dependent current-voltage properties in the range of 253–413 K were investigated and they follow the standard p-n heterojunction electron transport mechanism. The hybrid nanowire heterojunction shows good photovoltaic properties and good sensitivity toward visible light, and a responsivity of 3.23 mA/W under a reverse bias of 10 V was obtained. These results present potential applications in the future nanoelectronic and photonic devices based on organic and inorganic p-n heterojunction arrays. [ABSTRACT FROM AUTHOR]

A novel concept based on the use of solutions containing already qualified crystalline antimony-doped tin oxide SnO:Sb (ATO) nanoparticles has been developed. ATO nanoparticles are decorated by reduced graphene oxide (rGO) through a hydrothermal synthesis method. The electrical and optical properties of the graphene oxide films are investigated systematically. The sheet resistance ( R) of the ATO-rGO films decreases with the increase in the rGO content in the precursor solution. The R can be decreased after the ATO-rGO films annealing in the air for 1 h and can be further decreased by depositing Au on the surface of the films. The optimum property of the ATO-rGO film shows that the R is 80 Ω/□ and the transmittance is about 70 %. The ATO-rGO films are used as the anode of the organic solar cells. The anode film impact on the performance of the devices is studied. Finally, the power conversion efficiency (PCE) of the device based on the poly-(3-hexylthiophene): [6, 6]-phenyl C61-butyric acid methyl ester (PCBM) blended is 1.85 %, and the PCE of the device based on the poly-benzo[1,2-b:4,5-b′] dithio-phene thieno[3,4-b] thiophene:PCBM blended is 3.4 %. [ABSTRACT FROM AUTHOR]

In this article, we in situ fabricated copper sulfide (CuS) on fluorinated tin oxide (FTO) substrate using a low temperature and low cost hydrothermal method and then organic solar cells (OSCs) were fabricated by using a thin layer of CuS film as hole transporting layer (HTL). Our CuS films, consisting of two-dimensional (2D) intersected hexagonal nanosheets, are stoichiometric and show p-type electrical conductivity, a good transparency and a high hole mobility. The Fermi level, valence and conduction band energies for CuS HTL are characterized in detail through photoelectron spectroscopy studies. The small energy barrier between the valance band of CuS and the HOMO of poly(3-hexylthiophene) (P3HT) and the high hole mobility and electrical conductivity of CuS nanosheet film benefit for the hole transporting. Therefore, CuS HTL to OSCs results in a power conversion efficiency of 3.4% with P3HT and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the active layer, which is a 13.3% increase in performance than devices with a poly (3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) HTL. Therefore, low-cost, environmental friendly and stable CuS is an appropriate choice for hole transporting materials (HTMs) in OSCs. [ABSTRACT FROM AUTHOR]

Abstract: Copper sulfide (CuS) with nanosheet structure has been synthesized at a low temperature in situ on copper (Cu) film coated fluorine-doped tin oxide glass and bifacial quantum dot-sensitized solar cells (QDSSCs) were herein developed by using these CuS as counter electrodes (CEs). CuS is an environmental compatible and low toxic material. The obtained two-dimensional CuS nanosheet film presents high carrier mobility and exhibits highly catalytic performance for the polysulfide-based electrolyte. The QDSSC based on a CuS CE presents a power conversion efficiency (PCE) of 3.65% by optimizing the thickness of the Cu film under front illumination. The QDSSC based on a CuS CE prepared with a 200 nm thick Cu film shows a very close PCE under front and rear illuminations in which the values are as high as 2.70% and 2.40%, respectively. All the PCEs of the CuS CEs are much higher than that of the Pt CE (1.34%). [Copyright &y& Elsevier]

Abstract: A TiO2-embedded NiCl2 gel is prepared and used as growth catalyst to in situ synthesize binded, thick and porous carbon nanoparticles (CNPs) on Ti foil substrate with a simple flame synthesis method for dye sensitized solar cell (DSSC) counter electrode (CE) applications. The viscous gel catalyst can hold sufficient NiCl2 coated on substrate to make CNP layer thick. The embedded TiO2 can effectively separate the abundant NiCl2 components to active the Ni catalyst for CNP growth and then make CNP layer become porous. In addition, the TiO2 components can bind the porous CNP products to make them conductive. With an optimized TiO2 fraction, the CE shows high catalytic ability and electrical conductivity. By applying this CNP CE for DSSC, a photovoltaic conversion efficiency of 6.6% is achieved, which exceeds 6.5% of a reference cell using costly platinum as CE. Furthermore, the CNP structure is demonstrated beneficial to carrier transport by a mass transfer model. This easy and effective preparation method may have a potential application in general nanomaterial preparation. [Copyright &y& Elsevier]

The electrical characteristics and reliability of Hf-In-Zn-O (HIZO) metal-oxide-semiconductor capacitors (MOSCAPs) with a microporous SiO2-based electric-double-layer (EDL) dielectric were investigated. Experimental results indicated that the HfO2 interlayer could effectively improve the interface quality, thus leading to reduced interface states, suppressed hysteresis and decreased gate leakage current. Improved performance was achieved for the HIZO MOSCAPs with HfO2/EDL stack gate dielectrics (HECAPs), such as a large capacitance density of 0.7μF/cm2, an interface state density of 5.7×1011 eV−1/cm2, a fixed charge density of 1.9×1012 cm−2, a hysteresis voltage of 230mV and a gate leakage current density of 3×10−6 A/cm2 at +1V. Moreover, enhanced reliability of the HECAPs was obtained with an elevated dielectric breakdown voltage of 4.8V and a small increase (< 15 %) of gate leakage after gate bias stressing at 2V for 3600s. [ABSTRACT FROM AUTHOR]

Abstract: A nano-carbon composite with unique hierarchical porous structure has been effectively fabricated as dye sensitized solar cell (DSSC) counter electrode material by a simple and low-cost way. The fabrication process only employs spin-coating and then combustion by using sodium lauryl sulfate as a facile pore-forming precursor. The generated composite reveals high catalytic ability coupled with low electrical resistance owing to its unique structure. The power conversion efficiency of the resulting DSSC device reaches 6.5%, which is close to 6.6% of the referenced DSSC by using platinum as the counter electrode. A mass transfer model is built and it convincingly demonstrates that the composite architecture is beneficial to carrier transport. The fabrication strategy is simple and effective, and it has a great potential to be applied to DSSC fabrication on a large scale. [Copyright &y& Elsevier]

Abstract: Reproducible near-ultraviolet (near-UV) light-emitting diodes composed of ZnO nanorods (NRs) and p-GaN film using direct-bonding (DB) structure have been demonstrated and characterized. It is revealed that numerous p–n heterojunctions are formed between the ZnO NR top tips and GaN film after the thermal treatment. Dominant near-UV electroluminescence (EL) centered at 400nm was observed and green–orange defect-related light emissions were absent, which is probably due to the formation of high-quality p–n heterojunctions where the EL is stimulated. The EL origination and related carrier transport mechanism were discussed qualitatively in terms of photoluminescence results and energy band diagram. It''s hoped that the DB structure may serve as a feasible way in the future solid lighting applications. [Copyright &y& Elsevier]

Abstract: Efficient bulk-heterojunction (BHJ) polymer solar cells (PSCs) based on poly (3-hexylthiophene) (P3HT): indene-C60 bisadduct (ICBA) were fabricated with lithium fluoride (LiF) as electron collecting buffer layer and UV–ozone (UVO) treated molybdenum trioxide (MoO3) as hole collecting buffer layer. LiF is observed to be critical for the device performance, significantly enhancing the fill factor (FF) and the efficiency compared to the device without LiF layer. MoO3 layer is also critical to the device performance, efficiently extracting holes to prevent the exciton quenching and reducing the interfacial resistance because of alignment of energy band. After UVO treatment on MoO3 film, its surface morphology, transmittance and film quality can be improved, therefore, it is beneficial to the performance of the PSCs. The optimal thickness of MoO3 and UVO treatment time on MoO3 was 12nm and 15min, respectively. Based on these optimal parameters, a power conversion efficiency (PCE) of 6.43% was obtained under AM1.5G 100mW/cm2 illumination. [Copyright &y& Elsevier]

n-ZnO/p-Si heterojunction light emitting devices with and without a NiO intermediate layer were fabricated using a radio frequency magnetron sputtering system. Electroluminescence measurements revealed that the device with the NiO intermediate layer exhibits a sharper and stronger orange emission peaks at ∼670 nm compared with that of the device without the NiO layer. And the light output-current characteristic of the n-ZnO/NiO/p-Si heterojunction device follows a nearly linear relationship (L ∝ I) rather than the superlinear relationship (L ∝ I1.5) for the n-ZnO/p-Si heterojunction device. This work indicates that the NiO intermediate layer could effectively improve the performance of the n-ZnO/p-Si heterojunction light emitting device. [ABSTRACT FROM AUTHOR]

Abstract: Ultraviolet (UV) electroluminescence (EL) of n-ZnO:Al (AZO)/i-layer/n-GaN heterojunctions with different intrinsic layers has been obtained. Rectifying behavior and EL spectra of the heterojunctions are investigated at room temperature. Under positive voltage, a dominant UV emission peak around ∼370nm is observed for both AZO/i-ZnO/n-GaN and AZO/i-MgO/n-GaN heterojunctions. Nevertheless, the UV emission peak intensity of AZO/i-MgO/n-GaN heterojunction is much stronger than that of AZO/i-ZnO/n-GaN heterojunction at the same voltage. The threshold voltage of AZO/i-MgO/n-GaN heterostructured device is as low as 2.3V. The difference of EL spectra and the emission mechanism in these devices are discussed. [Copyright &y& Elsevier]

n-ZnO/HfO2/p-GaN based heterojunction light emitting diodes were fabricated using a radio frequency magnetron sputtering system. The electroluminescence measurements revealed that dominant violet emissions centered at around 415 nm were emitted and improved performances were observed for the devices with the HfO2 intermediate layer; the color of the devices could be tuned from violet (0.18, 0.10) to cold white (0.22, 0.20) by varying the Ar/O2 flow ratio during the deposition of HfO2, which are probably ascribed to the deep level emission bands in ZnO. The results were studied by peak-deconvolution with Gaussian functions and were discussed in terms of band diagram of the heterojunctions. [ABSTRACT FROM AUTHOR]

Abstract: A patterned method was proposed to realize large area fabrication of organic solar cells (OSCs) in series and parallel configurations. Series and parallel configurations of OSCs on ITO glass were designed and studied. Large open circuit voltage (V OC) was achieved in series OSCs, while the high short-circuit current (I SC) was achieved by using the parallel structure. A photovoltaic device composed of eight ITO/NiO/P3HT:PCBM/Al OSCs in series connection with area of 5×4cm2, V OC of 4.35V, I SC of 1.59mA and power conversion efficiency of 2.08% was achieved. This device succeeded in driving a group of 11 light emitting diodes. In addition, this patterned method a device with V OC of 1.5V and I SC of 18mA succeeded in driving a small motor. [Copyright &y& Elsevier]

Abstract: Efficient organic solar cells (OSCs) based on regioregular of poly (3-hexylthiophene): fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide coated glass substrates by using a sputtered indium oxide film as a hole-transporting layer (HTL). Optimized parameters for p-type In2O3 layer fabrication have been obtained through In2O3 layer sputtering temperature modulation. Based on this HTL, photovoltaic devices have been fabricated, and a power conversion efficiency up to 1.32% has been achieved. With the help of X-ray photoelectron spectroscopy and Hall-effect measurements, we conclude that the formation of In(OH)3/InOOH on the surface of In2O3 film could increase the electrical resistivity of films and affect the performance of OSC further. [Copyright &y& Elsevier]

We fabricate an ultraviolet (UV)/orange bicolor light emitting diode (LED) based on an n-ZnO/n-GaN isotype heterojunction, which presents a sharp ultraviolet emission centered at 367 nm and a broad orange emission centered at 640 nm under forward and reverse biases, respectively. Time dependence electroluminescence (EL) measurements reveal that this device shows good stability. The electroluminescence mechanism of the bicolor light emitting diode is discussed in terms of the material properties of the interfacial layer and the luminescence properties of the device in this work. [ABSTRACT FROM AUTHOR]

Abstract: Organic solar cells (OSCs) based on the blends of poly(3-hexylthiophene) and fullerene derivative [6, 6]-phenyl-C61 butyric acid methyl ester have been fabricated with p-type chromium oxide film as hole-transporting layer. The distribution of temperature and heat flow in vacuum chamber was investigated by temperature probes and finite element method. It is found that the two factors have significant effect on the quality of the thermally evaporated Al cathode. The bigger momentum impinging Al particles facilitates the formation of C–Al or C–O–Al bonds at the interface between photoactive layer and Al electrode, which is propitious to the electron transfer, and the corresponding devices have higher electron mobility. The higher substrate temperature that induced by thermal radiation during Al evaporation can act as a function of thermal annealing treatment, which can eliminate some electron traps and lead to better ohmic contacts for electrons to transport at the interface. The combination of the bigger momentum impinging Al particles and the higher substrate temperature can induce the improvement of electron mobility and OSC performance. [Copyright &y& Elsevier]

Abstract: The authors have attentively investigated the roles of the thermal annealing in the thin blended film of a novel low band-gap polymer poly[(4,4-bis(2-ethyl)cyclopenta- [2,1-b:3,4-b’]dithiophene)-2,6-diyl-alt-(5-octylthieo[3,4-b]pyrrole-4,6-dione)-1,3-diyl] (PCPDTTPD) and [6,6]-phenyl C60 butyric acid methyl ester (PCBM). The surface morphology, optical absorption spectra and carrier mobility of the PCPDTTPD:PCBM film as a function of annealing temperature were investigated. Open-circuit voltage as high as 0.86V was obtained in the PCPDTTPD:PCBM active layer based organic photovoltaics. The post-deposition annealing effects on the performance of solar cells also have been discussed. The results illustrated that the maximum power conversion efficiency of 2.01% was achieved in the as-cast devices. [Copyright &y& Elsevier]

Abstract: Efficient bulk-heterojunction (BHJ) (regioregular poly (3-hexylthiophene) (P3HT): (6, 6)-phenyl C61 butyric acid methyl ester (PCBM)) solar cells were fabricated with molybdenum trioxide (MoO3) and copper phthalocyanine (CuPc) as buffer layers. The insertion of MoO3 layer was found to be critical to the device performance, effectively extracting holes to prevent the exciton quenching and reducing the interfacial resistance because of alignment of energy levels. The introduction of CuPc buffer layer was observed to be ameliorative for device performance, further enlarging the visible absorption spectra range of the devices. The effect of the MoO3 and CuPc layer thickness on device performance was studied. The optimized thickness was achieved when MoO3 layer was 12nm and CuPc layer was 6nm, resulting in optimized power conversion efficiency (PCE) of 3.76% under AM1.5G 100mW/cm2 illumination. [Copyright &y& Elsevier]

Abstract: In this paper, we reported a simple method to increase the power conversion efficiencies (PCEs) of solar cells based on poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester derivatives blended active layer. The approach includes insertion of a discotic liquid crystal [2,3,6,7,10,11]-Hexabutoxytriphenylene (HAT4) at the interface between the active layer and a hole transporting layer. HAT4 molecules distribute in the active layer to form a more efficient pass way for carriers leading to improve the charge mobility. The experiments also included different hole transporting layers (HTLs) (PEDOT:PSS, MoO3 and NiO) deposited on fluorine-tin oxide substrates, respectively. The results showed that both short-circuit current (J SC) and fill factor (FF) were increased without open-circuit voltage sacrifice. Maximum 43% increase in PCE with the insertion of HAT4 for three kinds of HTLs was obtained in the devices compared with that of the reference ones. The mechanisms behind J SC and FF increase are discussed. [Copyright &y& Elsevier]

Abstract: Efficient organic solar cells based on the blends of poly (3-hexylthiophene) (P3HT):fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) composites have been fabricated by using the sputtered amorphous chromium oxide (ACO) film on fluorine-doped tin oxide (FTO) coated glass substrates as a hole-transporting layer (HTL). Through ACO layer sputtering temperature, film thickness and oxygen flow ratio optimization, the highest power conversion efficiency of 3.28% of FTO/ACO/P3HT:PCBM/Al solar cells on glass has been achieved under AM1.5G 100mW/cm2 illumination. It is found that the device with 10nm thick ACO sputtered at 473K and oxygen flow ratio f(O2) (O2/O2 +Ar)=40% shows the best photovoltaic properties. The photovoltaic properties in these devices are discussed in terms of the band diagrams and series resistance of the devices, and characteristics of ACO HTL. It is concluded that ACO is a suitable alternative to poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as a HTL. [Copyright &y& Elsevier]

Abstract: Efficient organic solar cells (OSCs) based on the blends of poly(3-hexylthiophene): fullerene derivative [6,6]-phenyl-C61 butyric acid methyl ester composites have been fabricated on fluorine-doped tin oxide coated glass substrates using the sputtered nitrogen doped amorphous chromium oxide (NACO) film as a hole-transporting layer (HTL). Optimized parameters for p-type NACO layer fabrication have been obtained through argon/oxygen/nitrogen flow ratio variations. Based on the HTL, the power conversion efficiency up to 3.17% has been achieved. With the help of X-ray photoelectron spectroscopy and Hall-effect measurements, we come to a conclusion that CrN in amorphous chromium oxide (ACO) film could prevent water dissociation and hydroxylation at defect sites on the ACO film surface, and reduce the electrical resistivity of films. The stability of NACO as HTL has been improved compared with that of ACO as HTL, which can improve the performance of OSC. [ABSTRACT FROM AUTHOR]

Abstract: Phase separation of the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) active layer (ATL) was investigated by varying their relative ratio in the organic solar cells (OSCs). With the help of the UV/visible spectrophotometer, optical microscopy and scanning electron microscope, we found that the cluster of PCBM at the interface or surface was affected by Al cathode, the composition of the blends and thermal annealing. The disc-like shape crystals of PCBM substituted for the needle-like ones at higher PCBM compositions at the ATL/Al interface, which led to stronger contacts and bigger contact area. It could make short circuit current density increase, but may affect the blend morphology and result in parallel resistance and open circuit voltage decreased with the PCBM ratio increasing from 40 to 60%. The microstructure of the P3HT:PCBM ATL, determined by the composition dependent phase separation, supported the optimized performance of the OSCs with the composition of 40–50% PCBM. [ABSTRACT FROM AUTHOR]

Abstract: We report efficient bulk-heterojunction [regioregular of poly(3-hexylthiophene) (P3HT):(6,6)-phenyl C61 butyric acid methyl ester (PCBM)] solar cells with a highly transparent and electrical conductive NiO film as hole transporting layer (HTL) on optimized Al doped zinc oxide (AZO) substrate. The highest power conversion efficiency (PCE) of 3.15% of AZO/NiO/P3HT:PCBM/Al solar cells was achieved through NiO nano-layer sputtering O2/Ar flow ratio, film thickness optimization and it was found that room temperature sputtered NiO at an O2/Ar ratio of 3:7 and with a thickness of 10nm shows the best photovoltaic properties. [ABSTRACT FROM AUTHOR]

Abstract: High κ HfO x N y film was deposited on amorphous InGaZnO (a-IGZO) by radio-frequency reactive sputtering using an HfO2 target in nitrogen plus argon ambience, the electrical characteristics and reliability of a-IGZO metal–insulator–semiconductor (MIS) capacitors were investigated. Experimental results indicate that the nitrogen incorporation into HfO2 can produce a strong nitride interfacial barrier layer, thus lead to reducing the interface state density, suppressing the hysteresis voltage, and decreasing the gate-leakage current. Improved performance has been achieved for HfO x N y gate dielectric a-IGZO MIS capacitors, with a interface state density of 5.1×1011 eV−1 cm−2, a gate-leakage current density of 3.9×10−5 A/cm2 at Vfb +1V, an equivalent permittivity of 24, and a hysteresis voltage of 105mV. Moreover, the enhanced reliability of Al/HfO x N y /a-IGZO MIS capacitor is observed with a small degradation of electrical characteristics after a high field stressing at 10MV/cm for 3600s. [Copyright &y& Elsevier]

Abstract: Polycrystalline p-type Cu x O films were deposited after the growth of HfO2 dielectric on Si substrate by pulsed laser deposition, and Cu x O metal-oxide-semiconductor (MOS) capacitors with HfO2/SiO2 stack gate dielectric were primarily fabricated and investigated. X-ray diffraction and X-ray photoelectron spectroscopy were applied to analyze crystalline structure and Cu+/Cu2+ ratios of Cu x O films respectively. SiO2 interlayer formed between the high-κ dielectric and substrate was estimated by the transmission electron microscope. Results of electrical characteristic measurement indicate that the permittivity of HfO2 is about 22, and the gate leakage current density of MOS capacitor with 11.3nm HfO2/SiO2 stack dielectrics is ∼10− 4 A/cm2. Results also show that the annealing in N2 can improve the quality of Cu x O/HfO2 interface and thus reduce the gate leakage density. [Copyright &y& Elsevier]

Abstract: Patterned carbon nanotube (CNT) arrays on Si substrate have been fabricated by using a two layer Sn/Ni catalyst in a diffusion ethanol flame. Vertically well-aligned CNT arrays were achieved on a Si substrate without any catalyst pretreatment. The Sn underlayer activated the substrates for CNT growth with Ni as catalyst, and provided a good contact between CNTs and the substrate, which is useful for field emission. Since the adhesion of Sn/Ni nanoparticles to the substrate is very strong, the growth of the CNTs follows a base-growth mode. The thickness of the Sn underlayer largely determines the diameter and diameter distribution of the as-grown CNTs. The morphologies and field electron emission properties of CNT arrays grown on Si substrates with different thicknesses of Sn and growth times have been investigated. The variation of emission current density was less than 5% during a 4h test under a field of 1.77V/µm. [Copyright &y& Elsevier]

Abstract: Three types of models, with various emitter shapes in planar electrodes, have been employed to investigate field electron emission characteristics by finite element method. With the model of “hemisphere on a post”, two definitions of field enhancement and field amplification factors and their relation have been discussed systemically at different anode locations. The field distribution in the gap, between emitter apex and anode, is quantified by a field saturation factor. Simulation indicates that field distribution is an important aspect for explaining the nonlinear variation of field amplification factor at different anode locations. Furthermore, the field saturation factor can reflect the saturation degree of field amplification factor. The findings can be used not only in the model of “hemisphere on a post” but also approximately in the models of “two-stage hemisphere on a post” and “hemi-ellipsoid on plane”. Therefore, the fact can be approximately applied to every protruding shape of emitter that is supposed. Comparisons with previously reported experimental and theoretical results are also given. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) have been grown directly on a Si substrate without a diffusion barrier in ethanol diffusion flame using Ni as the catalyst after a photoresist-assisted catalyst annealing process. The growth mechanism of as-synthesized CNTs is confirmed by scanning electron microscopy, high resolution transmission-electron microscopy and energy-dispersive spectroscopy. The photoresist is the key for the formation of active catalyst particles during annealing process, which then result in the growth of CNTs. The catalyst annealing temperature has been found to affect the morphologies and field electron emission properties of CNTs significantly. The field emission properties of as-grown CNTs are investigated with a diode structure and the obtained CNTs exhibit enhanced characteristics. This technique will be applicable to a low-cost fabrication process of electron-emitter arrays. [Copyright &y& Elsevier]

Abstract: In this article, we report ZnO nanorod samples grown on transparent conductive SnO2:F (FTO) glass substrates by two different growth routes through hydrothermal method in a closed autoclave. One route is one-step continuous growth for 10h. The other route is discrete multi-step growth for total 48h. In this process, fresh solution was repeatedly introduced in every step. The structural, photoluminescence (PL) and photovoltaic properties of the as-prepared nanorod arrays were investigated. The nanorod arrays obtained through multi-step growth show longer rods, higher aspect ratio, larger spacing, better crystalline quality. The PL spectrum of nanorod arrays obtained through multi-step growth shows a strong and sharp near-band-gap emission (UV) peak and a weak green–yellow emission (GY) peak (I UV/I GY =7.7), which also implies its good crystallinity and high optical quality. Dye-sensitized solar cells based on ZnO nanorod arrays were fabricated, and those grown with discrete multi-step procedure present better photovoltaic properties duo to its special morphology and better crystal quality. [Copyright &y& Elsevier]

Abstract: We reported the flame-synthesis of patterned multiwalled carbon nanotubes (CNTs) on silicon substrate by a shadow mask and their field emission properties. It was found that CNTs with tangled and curved morphology were preferentially grown around the cracked edges of Ni dot pattern. A crack-induced catalyst-activation growth mechanism was proposed. The patterned CNTs fabricated by such a simple flame-synthesis method exhibited good field emission characteristics with uniform emission patterns and reproducible and stable emission behaviors, although the CNTs possessed many defective graphite layers and showed relatively higher turn-on and threshold field than other reported CNTs grown by chemical vapor deposition. Our results demonstrated that such a low-cost and scaleable CNT pattern fabrication process can be expected to have favorable applications in field emission devices. [Copyright &y& Elsevier]

Abstract: The novel 2D snowflake-like ZnO structures have been self-assembly synthesized on SiO2/Si substrate coated with Pt strips by thermal evaporation of Zn power. Scanning electron microscopy, X-ray diffraction, transmission electron microscopy measurements showed that the snowflake-like ZnO possesses the perfect six-fold symmetric single-crystalline wurtzite structure. The room-temperature photoluminescence spectrum revealed a strong ultraviolet emission band at 382 nm. The possible growth process was also discussed. It was found that the deposition of thin layer of Pt strips is important for the formation of 2D snowflake-like ZnO structures. [Copyright &y& Elsevier]

Abstract: Vertically well-aligned single crystal ZnO nanorod arrays were synthesized and enhanced field electron emission was achieved with hafnium nitride (HfN x ) coating under proper sputtering condition. HfN x films with various composition have been coated on ZnO nanorod arrays using a reactive direct current (DC) magnetron sputtering system. Morphology and crystal configuration of the ZnO nanorod arrays were investigated by scanning electron microscopy and X-ray diffraction. The field emission properties of the coated and uncoated ZnO nanorod arrays were characterized. The as-grown ZnO nanorod arrays showed a turn-on electric field of 6.60 V μm−1 at a current density of 10 μA cm−2 and an emission current density of 1 mA cm−2 under the field of 9.32 V μm−1. While the turn-on electric field of the coated ZnO nanorod arrays sharply decreased to 2.42 V μm−1, an emission current density of 1 mA cm−2 under the field of only 4.30 V μm−1 can be obtained. A method to accurately measure the work function of the coated films was demonstrated. [Copyright &y& Elsevier]

Abstract: Nickel oxide thin films were deposited on fused silica and Si(100) substrates at different substrate temperatures ranging from room temperature to 400°C using radio frequency reactive magnetron sputtering from a Ni metal target in a mixture of O2 and Ar. With the increase of substrate temperature, nickel oxide films deposited on the Si substrates exhibit transition from amorphous to poly-crystalline structures with different preferred orientations of NiO(200) and (111). The films deposited at higher temperature exhibit higher Ni2+/Ni3+ ratio. With substrate temperature increasing from room temperature to 400°C, the electrical resistivities of nickel oxide films increase from (2.8±0.1)×10−2 to (8.7±0.1)Ωcm, and the optical band-gap energies increase from 3.65 to 3.88eV. A p-nickel oxide/n-zinc oxide heterojunction was fabricated to confirm the p-type conduction of nickel oxide thin film, which exhibited a steadily rectifying behavior. [Copyright &y& Elsevier]

Abstract: Hafnium nitride (Hf-N) thin films were deposited on fused silica at different N2 flow ratio (N2/N2 +Ar) using a reactive DC magnetron sputtering system. A gradual evolution in the composition of the films from Hf3N2, HfN, to higher nitrides was found through X-ray diffraction (XRD). Films of Hf3N2 and HfN show positive temperature coefficients of resistivity, while higher nitride has a negative one. Highly oriented growth of (001) Hf3N2 and NaCl-structure (100) HfN films were fabricated on fused silica substrate at relatively lower temperature of 300°C. The electrical resistivity values of both as-deposited and post-deposition annealed films were measured by a four-point probe method. The obtained minimum resistivity of as-deposited film is 20μΩcm, and this result shows potential application of HfN films as electrode materials in electronic devices. [Copyright &y& Elsevier]

Abstract: Vertically well-aligned single crystal ZnO nanorod arrays were synthesized and enhanced field electron emission was achieved after radio-frequency (rf) Ar plasma treatment. With Ar plasma treatment for 30min, flat tops of the as-grown ZnO nanorods have been etched into sharp tips without damaging ZnO nanorod geometrical morphologies and crystallinity. After the Ar ion bombardment, the emission current density increases from 2 to 20μAcm−2 at 9.0Vμm−1 with a decrease in turn-on voltage from 7.1 to 4.8Vμm−1 at a current density of 1μAcm−2, which demonstrates that the field emission of the as-grown ZnO nanorods has been efficiently enhanced. The scanning electron microscopy (SEM) results, in conjunction with the results of transmission electron microscopy (TEM), Raman spectroscopy and photoluminescence observation, are used to investigate the mechanisms of the field emission enhancement. It is believed that the enhancements can be mainly attributed to the sharpening of rod tops, and the decrease of electrostatic screening effect. [Copyright &y& Elsevier]

Abstract: ZnO 3D microstructures with nano-multipod have been self-assembly synthesized on a post-annealed Ag-coated silicon substrate by sintering the mixture of ZnO and graphite powders in Ar flow. SEM images show that the microstructure has a spherical core and multiple radial nanorods grown around its outside with diameter of about 1–2 μm and 50–200 nm, respectively. XRD investigation shows the ZnO multipods are of a wurtzite structure. The room temperature photoluminescence spectrum of the microstructures reveals a strong broad green emission band at 530 nm. It is found that the post-deposition annealing treatment of the Ag thin film is a key factor to control the formation of ZnO 3D microstructures. The possible growth process based on VLS mechanism is proposed. [Copyright &y& Elsevier]

Abstract: A type of optical degradation of aluminium-doped zinc oxide (AZO) films due to water electrolysis-induced reduction reaction was reported. An experiment was designed in which AZO films were immersed in a 0.01M NaOH aqueous solution as cathode to electrolyze water. Significant decreases in the optical transmission of the treated samples were observed. Studies by X-ray diffraction and scanning electron microscope showed that the degradation of AZO films was due to compositional and structural changes with the treatment of water electrolysis, which resulted from the reduction reaction of atomic hydrogen generated in the electrolysis of water. This optical degradation reflects the stability degradation of AZO films under water electrolysis environment. [Copyright &y& Elsevier]

Abstract: In this study, highly transparent conductive Ga-doped Zn0.9Mg0.1O (ZMO:Ga) thin films have been deposited on glass substrates by pulsed laser deposition (PLD) technique. The effects of substrate temperature and post-deposition vacuum annealing on structural, electrical and optical properties of ZMO:Ga thin films were investigated. The properties of the films have been characterized through Hall effect, double beam spectrophotometer and X-ray diffraction. The experimental results show that the electrical resistivity of film deposited at 200°C is 8.12×10−4 Ωcm, and can be further decreased to 4.74×10−4 Ωcm with post-deposition annealing at 400°C for 2h under 3×10−3 Pa. In the meantime, its band gap energy can be increased to 3.90eV from 3.83eV. The annealing process leads to improvement of (002) orientation, wider band gap, increased carrier concentration and blue-shift of absorption edge in the transmission spectra of ZMO:Ga thin films. [Copyright &y& Elsevier]

Abstract: Vertically well-aligned ZnO nanoridge, nanorod, nanorod-nanowall junction, and nanotip arrays have been successfully synthesized on Si (100) substrates using a pulsed laser deposition prepared ZnO film as seed layer by thermal evaporation method. Experimental results illustrated that the growth of different morphologies of ZnO nanostructures was strongly dependent upon substrate temperature. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies showed that the ZnO nanostructures were single crystals with a wurtzite structure. Compared with those of the other nanostructures, the photoluminescence (PL) spectrum of nanorod–nanowall junctions showed the largest intensity ratio of ultraviolet (UV) to yellow–green emission and the smallest full-width at half-maximum (FWHM) of the UV peak, reflecting the high optical quality and nearly defect free of crystal structure. The vertical alignment of the nanowire array on the substrate is attributed to the epitaxial growth of the nanostructures from the ZnO buffer layer. The growth mechanism was also discussed in detail. [Copyright &y& Elsevier]

Abstract: Arrays of aligned silicon nanowire (SiNW) were synthesized on a silicon (100) substrate by self-assembling electroless nanoelectrochemistry. Compared with that of bulk crystal silicon, the first-order Raman peak of the silver cap-removed SiNW arrays shows a downshift and asymmetric broadening due to the phonon quantum confinement effects, and intensity enhancement. Field electron emission from the SiNWs was also investigated. The turn-on field was found to be about 12V/μm at a current density of 0.01mA/cm2. These highly densified and ordered SiNW arrays can be expected to have favorable applications in vacuum electronic or optoelectronic devices. [Copyright &y& Elsevier]

Using highly conductive Al-doped ZnO (AZO) ceramic target, (0 0 2)-oriented transparent conductive AZO thin films are prepared by DC planar magnetron sputtering deposition on glass sheet substrate. Structural, electrical and optical properties of the films deposited at different temperatures and subsequently annealed at 400°C for 2 h under 10−3 Pa are characterized with various techniques. Experimental results show that the electrical resistivity of AZO thin films deposited at 320°C can be as low as 1.5×10−4 Ω cm with post-deposition annealing. The annealing process leads to improvement of (0 0 2) orientation, wider band gap, increased carrier concentration and blue shift of absorption edge in the transmission spectra of AZO thin films. [Copyright &y& Elsevier]

Using a highly conductive ZnO (ZnAl2O4) ceramic target, c axis-oriented and oxygen-deficient Al-doped ZnO (ZAO) thin films were prepared on glass sheet substrates by radio frequency (RF) planar magnetron sputtering. The structural, electrical and optical properties of the films (deposited at room temperature and annealed at different conditions) were characterized with various techniques. The experimental results show that the electrical resistivity of as-grown films can be decreased to 10−4 Ω cm level with post-deposition annealing at 400 °C for 2 h in a vacuum pressure of 10−5 torr. By increasing the annealing temperature, the oxygen vacancies and carrier concentration of ZAO thin film increase, and the absorption edge in the transmission spectra shifts toward the shorter wavelength side (blue shift). The oxygen vacancy plays an important role in the electrical conductivity. The more the oxygen vacancies exist in ZAO thin films, the higher the electrical conductivity will be. [Copyright &y& Elsevier]

Despite advances in mixed tin‐lead (Sn‐Pb) perovskite‐based solar cells, achieving both high‐efficiency and long‐term device stability remains a major challenge. Current device deficiencies stem partly from inefficient carrier transport, originating from defects and improper band energy alignment among the device's interfaces. Developing multifunctional interlayer materials simultaneously addressing the above concerns poses an excellent strategy. Herein, through molecular and crystal engineering, an amine‐functionalized C60 mono‐adduct derivative (C60‐2NH3 = bis(2‐aminoethyl) malonate‐C60) is utilized for the synthesis of the first crystalline fullerene‐based 2D metal halide semiconductor, namely (C60‐2NH3)Pb2I6. Single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C60‐2NH3 to the electronic density of states of the conduction band of (C60‐2NH3)Pb2I6. Utilization of C60‐2NH3 as an interlayer between a FA0.6MA0.4Pb0.7Sn0.3I3 perovskite and a C60 layer offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility. The corresponding perovskite solar cell (PSC) device achieved a power conversion efficiency (PCE) value of 21.64%, maintaining 90% of its initial efficiency, after being stored under a N2 atmosphere for 2400 h. This work sets the foundation for developing a new family of functional materials, namely Fullerene Metal Halide Semiconductors, targeting applications from photovoltaics to catalysis, transistors, and supercapacitors. [ABSTRACT FROM AUTHOR]

ZnO nanorod strain driving transistor (SDT) with 107 scale 'on'-'off' ratio has been fabricated on Kapton substrate by a single-step hydrothermal reaction. The transistor is driven by strain due to the change in Schottky barrier height caused by piezoelectric effect as well as the change of contact area between ZnO bridging nanorods. Moreover, via utilizing two SDTs on the top and bottom surfaces of the substrate as two complementary metal-oxide-semiconductor transistors, several logic operations such as inverter, NAND, NOR, XOR, MUX, and DEMUX with good rectifying behaviors have been demonstrated. [ABSTRACT FROM AUTHOR]

n-ZnO/p-silicon nanowire (SiNW) photodiodes were prepared by radio frequency reactive magnetron sputtering of n-type zinc oxide at room temperature on photoresist filled p-SiNWs, which were fabricated by electroless metal deposition method at 323 K. Our n-ZnO/p-SiNW photodiodes showed good temperature- and light-intensity dependence. They exhibited strong responsivities of 19.2 and 2.5 A/W for 254 and 1000 nm photons, respectively, under a reverse bias of 2 V with a strong peak of responsivity near 390 nm, the wavelength corresponding to the band gap of ZnO. These results present potential applications of n-ZnO/p-SiNW photodetectors in deep ultraviolet and near infrared regions. [ABSTRACT FROM AUTHOR]

Owing to their remarkable and adjustable optoelectronic properties, halide perovskites (HPs) have been regarded as a class of promising materials for various optoelectronic applications based on different energy conversion reactions, including photovoltaic cell, photocatalysis, electrocatalysis, and photoelectrochemical (PEC) systems. However, the low stability of HPs upon exposure to ambient conditions (e.g., water, heat, light, electricity) greatly hinders the practical applications of HPs. In the past few years, significant efforts have been devoted to enhancing the eventual stability of the perovskite‐based optoelectronic systems, mainly focusing on delivering improvements in the stabilities of halide perovskite materials and the relevant operation conditions of optoelectronic systems, which deserve in‐depth and systematic summaries. In this comprehensive review, the in‐depth environment‐induced decomposition mechanisms of typical HPs are elucidated. Simultaneously, the strategies for addressing the instability issues of halide perovskite materials are critically reviewed, including dimension control, compositional engineering, ligand passivation, and encapsulation engineering. Furthermore, the photoelectric applications based on the modified HPs and operation conditions are discussed systematically. In the last part of this review, future perspectives and outlooks toward the stability of HPs and their photoelectric applications are envisaged respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] Despite their excellent environmental stability, low defect density, and high carrier mobility, large- n quasi-two-dimensional halide perovskites (quasi-2DHPs) feature a limited application scope because of the formation of self-assembled multiple quantum wells (QWs) due to the similar thermal stabilities of large- n phases. However, large- n quasi-phase-pure 2DHPs (quasi-PP-2DHPs) can solve this problem perfectly. This review discusses the structures, formation mechanisms, and photoelectronic and physical properties of quasi-PP-2DHPs, summarises the corresponding single crystals, thin films, and heterojunction preparation methods, and presents the related advances. Moreover, we focus on applications of large- n quasi-PP-2DHPs in solar cells, photodetectors, lasers, light-emitting diodes, and field-effect transistors, discuss the challenges and prospects of these emerging photoelectronic materials, and review the potential technological developments in this area. [ABSTRACT FROM AUTHOR]

Weak‐light imaging holds immense significance in various imaging applications. Recently, there has been significant research focused on 2D perovskites for photodetectors (PDs), owing to their superior photoelectric properties. However, the utilization of 2D perovskites for high‐performance weak‐light detection remains limited, and there is a notable absence of demonstration in weak‐light ultraviolet (UV) imaging. Herein, a high‐sensitive UV detectors with an ultra‐low detection limit for weak‐light imaging are demonstrated, utilizing 2D perovskite (PA)2PbBr4 (PPB) single crystals (SCs). Leveraging the exceptional quality of SCs, the PPB‐based PD exhibits outstanding operational performances, including a low dark current of 0.735 pA, high on/off ratio of 4150 under 263.3 mW cm−2 illimitation, and extensive linear dynamic range of 153.61 dB, which is currently the highest reported value among 2D perovskite SC detectors. Notably, PPB PDs demonstrate a remarkable response under 5.49 nW cm−2 illumination, enabling it to exhibit outstanding photo‐response with an excellent detectivity of 2.3 × 1013 Jones and responsivity of 2.22 A W−1. Importantly, high‐resolution images are successfully obtained under weak‐light illumination. These findings underscore the immense potential of 2D perovskite for UV weak‐light imaging. [ABSTRACT FROM AUTHOR]

Perovskite single crystals (SCs) have gained significant interest in various applications owing to their superior optoelectrical and physical characteristics as compared to polycrystalline films. However, a considerable portion of incident light is typically reflected at the surface of perovskite SCs, leading to insufficient light absorption within the crystal bulk, ultimately resulting in reduced performance of SC‐based photodetectors. In the present work, an inverted pyramid‐shaped structure is in situ introduced on the surface of an MAPbBr3 SC during the crystal growth process, which can reduce light reflection in the surface region and enhance light absorption of the SC. Additionally, the hydrophobic small molecule copper (II) phthalocyanine (CuPc) is thermally evaporated onto the SC, forming a CuPc/MAPbBr3 heterojunction for the first time. The CuPc/pyramid‐shaped MAPbBr3 heterojunction‐based photodetector exhibits self‐powered characteristics and superior optoelectrical performance, achieving a photocurrent of greater than 10−5 A (10−7 A), a responsiveness of 257 mA W−1 (8.84 mA W−1), and a detection rate of 2.98 × 1012 Jones (1.02 × 1011 Jones) at −2 V (0 V) bias. Simultaneously, the device demonstrates excellent long‐term stability under high humidity conditions, retaining 90.5% of its initial photocurrent even after 60 days in a 60–80% humidity environment. [ABSTRACT FROM AUTHOR]

A response to a letter to the editor about the article "Deep ultraviolet and near infrared photodiode based on n-ZnO/p-silicon nanowire heterojunction at low temperature," is presented.