p‐Type Beta‐Silver Vanadate Nanoribbons for Nanoelectronic Devices with Tunable Electrical Properties

β‐AgVO₃, as a stable phase and a typical silver vanadium oxide, has performed special ionic and electrical properties. The construction of nanoelectronic devices based on ultralong β‐AgVO₃ nanoribbons (NRs) is reported, including nano‐field‐effect transistor (nano‐FET) and nano‐Schottky barrier diode (nano‐SBD). Owing to the specific channel structure and ion conductivity, the nano‐FET exhibits typical p‐type semiconductor characteristics and the nano‐SBD with Al contacts performs a prominent rectifying behavior with an on/off ratio of up to 10³. Besides, tunable electrical transport properties can be achieved by tailoring the material properties, and it is demonstrated that the bridging NR numbers and diameters have a positive effect on electrical transport properties, while a complex variation trend is observed in the case of surface modification by photo‐irradiation. Electron spin resonance (ESR) spectrum further illuminates that the induced vacancies play an important role on the electrical transport properties of β‐AgVO₃ nanoribbons. Easy access to the ultralong β‐AgVO₃ NRs makes them a promising candidate for potential applications in nanoelectronic devices.     

A Molecular Glass for Deep‐Blue Organic Light‐Emitting Diodes Comprising a 9,9′‐Spirobifluorene Core and Peripheral Carbazole Groups

Novel fluorene‐based compounds, TCPC‐6 and TCPC‐4, with rigid central spirobifluorene cores and peripheral carbazole groups are synthesized using the Suzuki coupling reaction. The optical, electrochemical, and thermal properties of these compounds are characterized. The compounds show strong deep‐blue emission both in solution and as thin films. Both TCPC‐6 and TCPC‐4 exhibit amorphous morphologies in the solid state with high glass transition temperatures (T_g) of 108 and 143 °C, respectively. Atomic force microscopy (AFM) measurements indicate that high‐quality amorphous films of these novel compounds can be prepared by spin‐coating. The oxidation potentials of TCPC‐6 and TCPC‐4 are significant lower than that of model compounds without peripheral carbazole groups, which suggests that these compounds have relatively high highest occupied molecular orbital (HOMO) energy levels and better hole‐injection capabilities. Light‐emitting devices fabricated by spin‐coating films of these molecules exhibit deep‐blue emission with Commission Internationale de l'Eclairage (CIE) chromaticity coordinates (x, y) of (0.16, 0.05); the devices fabricated using spin‐coated TCPC‐6 and TCPC‐4 layers exhibit high luminance efficiencies of 1.35 and 0.90 cd A^–1 (with external quantum efficiencies of 3.72 and 2.47 %), respectively.     

Controlled Growth and Reliable Thickness‐Dependent Properties of Organic–Inorganic Perovskite Platelet Crystal

Organolead halide perovskites (e.g., CH₃NH₃PbI₃) have caught tremendous attention for their excellent optoelectronic properties and applications, especially as the active material for solar cells. Perovskite crystal quality and dimension is crucial for the fabrication of high‐performance optoelectronic and photovoltaic devices. Herein the controlled synthesis of organolead halide perovskite CH₃NH₃PbI₃ nanoplatelets on SiO₂/Si substrates is investigated via a convenient two‐step vapor transport deposition technique. The thickness and size of the perovskite can be well‐controlled from few‐layers to hundred nanometers by altering the synthesis time and temperature. Raman characterizations reveal that the evolutions of Raman peaks are sensitive to the thickness. Furthermore, from the time‐resolved photoluminescence measurements, the best optoelectronic performance of the perovskite platelet is attributed with thickness of ≈30 nm to its dominant longest lifetime (≈4.5 ns) of perovskite excitons, which means lower surface traps or defects. This work supplies an alternative to the synthesis of high‐quality organic perovskite and their possible optoelectronic applications with the most suitable materials.     

Controlled Polarizability of One‐Nanometer‐Thick Oxide Nanosheets for Tailored,High‐κ Nanodielectrics

An important challenge in current microelectronics research is the development of techniques for making smaller, higher‐performance electronic components. In this context, the fabrication and integration of ultrathin high‐κ dielectrics with good insulating properties is an important issue. Here, we report on a rational approach to produce high‐performance nanodielectrics using one‐nanometer‐thick oxide nanosheets as a building block. In titano niobate nanosheets (TiNbO₅, Ti₂NbO₇, Ti₅NbO₁₄), the octahedral distortion inherent to site‐engineering by Nb incorporation results in a giant molecular polarizability, and their multilayer nanofilms exhibit a high dielectric constant (160–320), the largest value seen so far in high‐κ nanofilms with thickness down to 10 nm. Furthermore, these superior high‐κ properties are fairly temperature‐independent with low leakage‐current density (<10^?7 A cm^?2). This work may provide a new recipe for designing nanodielectrics desirable for practical high‐κ devices.     

Low‐Work‐Function Surface Formed by Solution‐Processed and Thermally Deposited Nanoscale Layers of Cesium Carbonate

Nanostructured layers of Cs₂CO₃ are shown to function very effectively as cathodes in organic electronic devices because of their good electron‐injection capabilities. Here, we report a comprehensive study of the origin of the low work function of nanostructured layers of Cs₂CO₃ prepared by solution deposition and thermal evaporation. The nanoscale Cs₂CO₃ layers are probed by various characterization methods including current–voltage (I–V) measurements, photovoltaic studies, X‐ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), and impedance spectroscopy. It is found that thermally evaporated Cs₂CO₃ decomposes into CsO₂ and cesium suboxides. The cesium suboxides dope CsO₂, yielding a heavily doped n‐type semiconductor with an intrinsically low work function. As a result, devices fabricated using thermally evaporated Cs₂CO₃ are relatively insensitive to the choice of the cathode metal. The reaction of thermally evaporated Cs₂CO₃ with Al can further reduce the work function to 2.1 eV by forming an Al–O–Cs complex. Solution‐processed Cs₂CO₃ also reduces the work function of Au substrates from 5.1 to 3.5 eV. However, devices prepared using solution‐processed Cs₂CO₃ exhibit high efficiency only if a reactive metal such as Al or Ca is used as the cathode metal. A strong chemical reaction occurs between spin‐coated Cs₂CO₃ and thermally evaporated Al. An Al–O—Cs complex is formed as a result of this chemical reaction at the interface, and this layer significantly reduces the work function of the cathode. Finally, impedance spectroscopy results prove that this layer is highly conductive.     

Modular Layer‐by‐Layer Assembly of Polyelectrolytes,Nanoparticles, and Molecular Catalysts into Solar‐to‐Chemical Energy Conversion Devices

The design and fabrication of solar‐to‐chemical energy conversion devices are enabled through interweaving multiple components with various morphologies and unique functions using a versatile layer‐by‐layer assembly method. Cationic and anionic polyelectrolytes are used as an electrostatic adhesive to assemble the following functional materials: plasmonic Ag nanoparticles for improved light harvesting, upconversion nanoparticles for utilization of near‐infrared light, and polyoxometalate water oxidation catalysts for enhanced catalytic activity. Polyelectrolytes also have an additional function of passivating the surface recombination centers of the underlying photoelectrode. These functional components are precisely assembled on a model photoanode (e.g., Fe₂O₃ and BiVO₄) in a desired order and various combinations without degradation of their intrinsic properties. As a result, the performance of water oxidation photoanodes is synergistically enhanced. This study can enable the design and fabrication of novel solar‐to‐chemical energy conversion devices.     

Anti‐Ferromagnet Controlled Tunneling Magnetoresistance

The requirement for high‐density memory integration advances the development of newly structured spintronic devices, which have reduced stray fields and are insensitive to magnetic field perturbations. This could be visualized in magnetic tunnel junctions incorporating anti‐ferromagnetic instead of ferromagnetic electrodes. Here, room‐temperature anti‐ferromangnet (AFM)‐controlled tunneling anisotropic magnetoresistance in a novel perpendicular junction is reported, where the IrMn AFM stays immediately at both sides of AlO_x tunnel barrier as the functional layers. Bi‐stable resistance states governed by the relative arrangement of uncompensated anti‐ferromagnetic IrMn moments are obtained here, rather than the traditional spin‐valve signal observed in ferromagnet‐based tunnel junctions. The experimental observation of room‐temperature tunneling magnetoresistance controlled directly by AFM is practically significant and may pave the way for new‐generation memories based on AFM spintronics.     

Investigation of TDAPBs as hole‐transporting materials for organic light‐emitting devices (OLEDs)

The performance of organic light‐emitting devices (OLEDs) is strongly influenced by the electronic properties of the employed materials. In order to determine the effect of these materials' parameters, several different hole‐transporting 1,3,5‐tris(4‐diphenylaminophenyl)benzenes (TDAPBs) were synthesised. These TDAPBs contained different substituents, different numbers of substituents and different positions of theses substituents. For the evaluation of the electronic properties, cyclic voltammetry was employed in order to determine the HOMO values, and time‐of‐flight (TOF) measurements to obtain the hole mobilities. OLEDs were prepared consisting of the TDAPBs blended in a polymer matrix, and of Alq₃ as electron‐conducting and light‐emitting layer. These devices were investigated regarding their current density/voltage characteristics, efficiencies, onset voltages for electroluminescence, and lifetimes. For hole‐transporting blend systems an exponential relationship between the current density and the HOMO levels of the TDAPBs was found. However, even though the HOMO values cover a range from −5.09 to −5.35 eV, no effects on the performance of the OLEDs were detected for electroluminescent two‐layer systems. In this case the initial voltage seems to be a determining parameter for the behaviour of the devices during operation. Copyright © 1999 John Wiley & Sons, Ltd.     

n‐Doping of a Low‐Electron‐Affinity Polymer Used as an Electron‐Transport Layer in Organic Light‐Emitting Diodes

n‐Doping electron‐transport layers (ETLs) increases their conductivity and improves electron injection into organic light‐emitting diodes (OLEDs). Because of the low electron affinity and large bandgaps of ETLs used in green and blue OLEDs, n‐doping has been notoriously more difficult for these materials. In this work, n‐doping of the polymer poly[(9,9‐dioctylfluorene‐2,7‐diyl)‐alt‐(benzo[2,1,3]thiadiazol‐4,7‐diyl)] (F8BT) is demonstrated via solution processing, using the air‐stable n‐dopant (pentamethylcyclopentadienyl)(1,3,5‐trimethylbenzene)ruthenium dimer [RuCp*Mes]₂. Undoped and doped F8BT films are characterized using ultraviolet and inverse photoelectron spectroscopy. The ionization energy and electron affinity of the undoped F8BT are found to be 5.8 and 2.8 eV, respectively. Upon doping F8BT with [RuCp*Mes]₂, the Fermi level shifts to within 0.25 eV of the F8BT lowest unoccupied molecular orbital, which is indicative of n‐doping. Conductivity measurements reveal a four orders of magnitude increase in the conductivity upon doping and irradiation with ultraviolet light. The [RuCp*Mes]₂‐doped F8BT films are incorporated as an ETL into phosphorescent green OLEDs, and the luminance is improved by three orders of magnitude when compared to identical devices with an undoped F8BT ETL.     

The Influence of the Phase Morphology on the Optoelectronic Properties of Light‐Emitting Electrochemical Cells

We report on the morphological aspects of thin films prepared from a blue–green light‐emitting conjugated polymer, (methyl‐substituted ladder‐type poly(p‐phenylene, mLPPP)), blended with a solid‐state electrolyte composed either by a crown ether, dicyclohexano‐18‐crown‐6 (DCH18C6), or a high‐molecular‐weight poly(ethylene oxide) (HMWPEO), and a Li salt, lithium trifluoromethanesulfonate (LiCF₃SO₃, Li triflate (LiTf)), as they have been successfully applied in light‐emitting electrochemical cells (LECs). The surface morphologies of the blend layers were investigated using atomic force microscopy (AFM) in tapping mode, and the ion distribution was probed using X‐ray analysis by means of energy‐dispersive X‐ray spectrometry (EDXS) in the scanning electron microscope (SEM). We show that the two different phase‐separation processes, the complexation tendencies of the ionic species as well as the ionic transport numbers, have tremendous influence on the performances of the corresponding LECs, revealing either rectifying or symmetric optoelectronic characteristics in forward and reverse bias directions. This opens up new possibilities for tuning the optoelectronic properties of ion‐supported organic electronic devices.     

Back‐contacted back‐junction n‐type silicon solar cells featuring an insulating thin film for decoupling charge carrier collection and metallization geometry

In this study, back‐contacted back‐junction n‐type silicon solar cells featuring a large emitter coverage (point‐like base contacts), a small emitter coverage (point‐like base and emitter contacts), and interdigitated metal fingers have been fabricated and analyzed. For both solar cell designs, a significant reduction of electrical shading losses caused by an increased recombination in the non‐collecting base area on the rear side was obtained. Because the solar cell designs are characterized by an overlap of the B‐doped emitter and the P‐doped base with metal fingers of the other polarity, insulating thin films with excellent electrical insulation properties are required to prevent shunting in these overlapping regions. Thus, with insulating thin films, the geometry of the minority charge carrier collecting emitter diffusion and the geometry of the interdigitated metal fingers can be decoupled. In this regard, plasma‐enhanced chemical vapor deposited SiO₂ insulating thin films with various thicknesses and deposited at different temperatures have been investigated in more detail by metal‐insulator‐semiconductor structures. Furthermore, the influence of different metal layers on the insulation properties of the films has been analyzed. It has been found that by applying a SiO₂ insulating thin film with a thickness of more than 1000 nm and deposited at 350 °C to solar cells fabricated on 1 Ω cm and 10 Ω cm n‐type float‐zone grown silicon substrates, electrical shading losses could be reduced considerably, resulting in excellent short‐circuit current densities of more than 41 mA/cm² and conversion efficiencies of up to 23.0%. Copyright © 2012 John Wiley & Sons, Ltd.     

Cover Picture: Low‐Work‐Function Surface Formed by Solution‐Processed and Thermally Deposited Nanoscale Layers of Cesium Carbonate (Adv. Funct. Mater. 12/2007)

The cover shows the structure of an efficient polymer light emitting diode (PLED) and its energy diagram at the interface between aluminum (Al) and a Cs₂CO₃ interfacial layer. It reveals the origin of enhanced electron injection from the Al electrode due to the low work function of a thermally evaporated Cs₂CO₃ layer, as reported on p. 1966 by Jinsong Huang, Zhen Xu, and Yang Yang. Pictures of the white‐ and red‐emitting PLEDs are also shown. Nanostructured layers of Cs₂CO₃ are shown to function very effectively as cathodes in organic electronic devices because of their good electron‐injection capabilities. Here, we report a comprehensive study of the origin of the low work function of nanostructured layers of Cs₂CO₃ prepared by solution deposition and thermal evaporation. The nanoscale Cs₂CO₃ layers are probed by various characterization methods including current–voltage (I–V) measurements, photovoltaic studies, X‐ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), and impedance spectroscopy. It is found that thermally evaporated Cs₂CO₃ decomposes into CsO₂ and cesium suboxides. The cesium suboxides dope CsO₂, yielding a heavily doped n‐type semiconductor with an intrinsically low work function. As a result, devices fabricated using thermally evaporated Cs₂CO₃ are relatively insensitive to the choice of the cathode metal. The reaction of thermally evaporated Cs₂CO₃ with Al can further reduce the work function to 2.1 eV by forming an Al–O–Cs complex. Solution‐processed Cs₂CO₃ also reduces the work function of Au substrates from 5.1 to 3.5 eV. However, devices prepared using solution‐processed Cs₂CO₃ exhibit high efficiency only if a reactive metal such as Al or Ca is used as the cathode metal. A strong chemical reaction occurs between spin‐coated Cs₂CO₃ and thermally evaporated Al. An Al–O—Cs complex is formed as a result of this chemical reaction at the interface, and this layer significantly reduces the work function of the cathode. Finally, impedance spectroscopy results prove that this layer is highly conductive.     

Helical 3D‐Printed Metal Electrodes as Custom‐Shaped 3D Platform for Electrochemical Devices

3D‐printing represents an emerging technology that can revolutionize the way object and functional devices are fabricated. Here the use of metal 3D printing is demonstrated to fabricate bespoke electrochemical stainless steel electrodes that can be used as platform for different electrochemical applications ranging from electrochemical capacitors, oxygen evolution catalyst, and pH sensor by means of an effective and controlled deposition of IrO₂ films. The electrodes have been characterized by scanning electrode microscopy and energy dispersive X‐ray spectroscopy before the electrochemical testing. Excellent pseudocapacitive as well as catalytic properties have been achieved with these 3D printed steel‐IrO₂ electrodes in alkaline solutions. These electrodes also demonstrate Nernstian behavior as pH sensor. This work represents a breakthrough in on‐site prototyping and fabrication of highly tailored electrochemical devices with complex 3D shapes which facilitate specific functions and properties.     

Unexpected Propeller‐Like Hexakis(fluoren‐2‐yl)benzene Cores for Six‐Arm Star‐Shaped Oligofluorenes: Highly Efficient Deep‐Blue Fluorescent Emitters and Good Hole‐Transporting Materials

Grafting six fluorene units to a benzene ring generates a new highly twisted core of hexakis(fluoren‐2‐yl)benzene. Based on the new core, six‐arm star‐shaped oligofluorenes from the first generation T1 to third generation T3 are constructed. Their thermal, photophysical, and electrochemical properties are studied, and the relationship between the structures and properties is discussed. Simple double‐layer electroluminescence (EL) devices using T1–T3 as non‐doped solution‐processed emitters display deep‐blue emissions with Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.08) for T1 , (0.16, 0.08) for T2 , and (0.16, 0.07) for T3 . These devices exhibit excellent performance, with maximum current efficiency of up to 5.4 cd A^?1, and maximum external quantum efficiency of up to 6.8%, which is the highest efficiency for non‐doped solution‐processed deep‐blue organic light‐emitting diodes (OLEDs) based on starburst oligofluorenes, and is even comparable with other solution‐processed deep‐blue fluorescent OLEDs. Furthermore, T2‐ and T3‐ based devices show striking blue EL color stability independent of driving voltage. In addition, using T0–T3 as hole‐transporting materials, the devices of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS)/ T0–T3 /tris(8‐hydroxyquinolinato)aluminium (Alq₃)/LiF/Al achieve maximum current efficiencies of 5.51–6.62 cd A^?1, which are among the highest for hole‐transporting materials in identical device structure.     

Large‐Area Ordered Quantum‐Dot Monolayers via Phase Separation During Spin‐Casting

We investigate a new method for forming large‐area (> cm²) ordered monolayers of colloidal nanocrystal quantum dots (QDs). The QD thin films are formed in a single step by spin‐casting a mixed solution of aromatic organic materials and aliphatically capped QDs. The two different materials phase separate during solvent drying, and for a predefined set of conditions the QDs can assemble into hexagonally close‐packed crystalline domains. We demonstrate the robustness and flexibility of this phase‐separation process, as well as how the properties of the resulting films can be controlled in a precise and repeatable manner. Solution concentration, solvent ratio, QD size distribution, and QD aspect ratio affect the morphology of the cast thin‐film structure. Controlling all of these factors allows the creation of colloidal‐crystal domains that are square micrometers in size, containing tens of thousands of individual nanocrystals per grain. Such fabrication of large‐area, engineered layers of nanoscale materials brings the beneficial properties of inorganic QDs into the realm of nanotechnology. For example, this technique has already enabled significant improvements in the performance of QD light‐emitting devices.     

Leaf‐like Graphene Oxide with a Carbon Nanotube Midrib and Its Application in Energy Storage Devices

Graphene oxide (GO) has recently attracted a great deal of attention because of its heterogeneous chemical and electronic structures and its consequent exhibition of a wide range of potential applications, such as plastic electronics, optical materials, solar cells, and biosensors. However, its insulating nature also limits its application in some electronic and energy storage devices. In order to further widen the applications of GO, it is necessary to keep its inherent characteristics while improving its conductivity. Here, a novel leaf‐like GO with a carbon nanotube (CNT) midrib is developed using vapor growth carbon fiber (VGCF) through the conventional Hummers method. The CNT midrib provides a natural electron diffusion path for the leaf‐like GO, and therefore, this leaf‐like GO with a CNT midrib displays excellent performance when applied in energy storage devices, including Li‐O₂ batteries, Li‐ion batteries, and supercapacitors.     

Amphiphilic Poly(p‐phenylene)s for Self‐Organized Porous Blue‐Light‐Emitting Thin Films

Micro‐ and nanostructuring of conjugated polymers are of critical importance in the fabrication of molecular electronic devices as well as photonic and bandgap materials. The present report delineates the single‐step self‐organization of highly ordered structures of functionalized poly(p‐phenylene)s without the aid of either a controlled environment or expensive fabrication methodologies. Microporous films of these polymers, with a honeycomb pattern, were prepared by direct spreading of the dilute polymer solution on various substrates, such as glass, quartz, silicon wafer, indium tin oxide, gold‐coated mica, and water, under ambient conditions. The polymeric film obtained from C₁₂PPPOH comprises highly periodic, defect‐free structures with blue‐light‐emitting properties. It is expected that such microstructured, conjugated polymeric films will have interesting applications in photonic and optoelectronic devices. The ability of the polymer to template the facile micropatterning of nanomaterials gives rise to hybrid films with very good spatial dispersion of the carbon nanotubes.     

Printable Organic‐Inorganic Nanoscale Multilayer Gate Dielectrics for Thin‐Film Transistors Enabled by a Polymeric Organic Interlayer

Here, a new approach to the layer‐by‐layer solution‐processed fabrication of organic/inorganic hybrid self‐assembled nanodielectrics (SANDs) is reported and it is demonstrated that these ultrathin gate dielectric films can be printed. The organic SAND component, named P‐PAE, consists of polarizable π‐electron phosphonic acid‐based units bound to a polymeric backbone. Thus, the new polymeric SAND (PSAND) can be fabricated either by spin‐coating or blade‐coating in air, by alternating P‐PAE, a capping reagent layer, and an ultrathin ZrOx layer. The new PSANDs thickness vary from 6 to 15 nm depending on the number of organic‐ZrOx bilayers, exhibit tunable film thickness, well‐defined nanostructures, large electrical capacitance (up to 558 nF cm^?2), and good insulating properties (leakage current densities as low as 10^?6 A cm^?2). Organic thin‐film transistors that are fabricated with representative p‐/n‐type organic molecular/polymeric semiconducting materials, function well at low voltages (<3.0 V). Furthermore, flexible TFTs fabricated with PSAND exhibit excellent mechanical flexibility and good stress stability, offering a promising route to low operating voltage flexible electronics. Finally, printable PSANDs are also demonstrated and afford TFTs with electrical properties comparable to those achieved with the spin‐coated PSAND‐based devices.     

Surface‐Functionalization‐Mediated Direct Transfer of Molybdenum Disulfide for Large‐Area Flexible Devices

The transfer of synthesized large‐area 2D materials to arbitrary substrates is expected to be a vital step for the development of flexible device fabrication processes. The currently used hazardous acid‐based wet chemical etching process for transferring large‐area MoS₂ films is deemed to be unsuitable because it significantly degrades the material and damages growth substrates. Surface energy‐assisted water‐based transfer processes do not require corrosive chemicals during the transfer process; however, the concept is not investigated at the wafer scale due to a lack of both optimization and in‐depth understanding. In this study, a wafer‐scale water‐assisted transfer process for metal–organic chemical vapor‐deposited MoS₂ films based on the hydrofluoric acid treatment of a SiO₂ surface before the growth is demonstrated. Such surface treatment enhances the strongly adhering silanol groups, which allows the direct transfer of large‐area, continuous, and defect‐free MoS₂ films; it also facilitates the reuse of growth substrate. The developed transfer method allows direct fabrication of flexible devices without the need for a polymeric supporting layer. It is believed that the proposed method can be an alternative defect‐ and residue‐free transfer method for the development of MoS₂‐based next‐generation flexible devices.     

Direct Growth of Nanographene on Silicon with Thin Oxide Layer for High‐Performance Nanographene‐Oxide‐Silicon Diodes

Graphene‐silicon based configurations are attracting great attention for their potential application as electronics and optoelectronics. For their practical use, it is still limited by the configuration fabrication process. In this paper, a catalyst‐free method is reported to directly grow nanographene on silicon covered with a thin oxide layer to form nanographene‐oxide‐silicon configurations. Compared with previously reported nanographene‐silicon Schottky junctions, the nanographene‐oxide‐silicon structures exhibit a high performance on electronic and photovoltaic properties. The reverse leakage current of the nanographene‐oxide‐silicon is suppressed from over 10^?5 A down to 10^?8 A and the rectifier ratio is greatly enhanced from less than 5 up to 10³. The photovoltage is enhanced over 50 times. The nanographene‐oxide‐silicon structures exhibit especially ultrasensitive to weak light at a photovoltage working mode, which exceeds up to 10⁶ V/W at the light power of 0.025 μW. Due to the source material for nanographene is photoresist and the fabrication process is mainly based on the current‐used photolithography and silicon technique, the developed nanographene‐oxide‐silicon structures are very easy for device fabrication, integration, and miniaturization, and could be a promising way to produce metal‐free graphene‐silicon based electronics and optoelectronics for commercial use.