Space Charge Limited Current Research Articles

Ballistic-like space-charge-limited currents in halide perovskites at room temperature

The emergence of halide perovskites in photovoltaics has diversified the research on this material family and extended their application toward several fields in the optoelectronics, such as photo- and ionizing-radiation-detectors. One of the most basic characterization protocols consists of measuring the dark current–voltage (J−V) curve of symmetrically contacted samples for identifying the different regimes of the space-charge-limited current (SCLC). Customarily, J∝Vn indicates the Mott–Gurney law when n≈2 or the Child–Langmuir ballistic regime of SCLC when n=3/2. The latter has been found in perovskite samples. Herein, we start by discussing the interpretation of J∝V3/2 in relation to the masking effect of the dual electronic–ionic conductivity in halide perovskites. However, we do not discard the actual occurrence of SCLC transport with ballistic-like trends. Therefore, we introduce the models of quasi-ballistic velocity-dependent dissipation (QvD) and the ballistic-like voltage-dependent mobility (BVM) regimes of SCLC. The QvD model is shown to better describe electronic kinetics, whereas the BVM model results are suitable for describing both electronic and ionic kinetics in halide perovskites as a particular case of the Poole–Frenkel ionized-trap-assisted transport. The proposed formulations can be used as the characterization of effective mobilities, charge carrier concentrations and times-of-flight from J–V curves, and resistance from impedance spectroscopy spectra.

Absence of Space-Charge-Limited Current in Unconventional Field Emission

For field emission (FE), it is widely expected that its emitting current density $J$ will become space-charge-limited current (SCLC) within a gap spacing $D$ biased at sufficiently large voltage $V$. In this paper, we reveal a peculiar finding in which this expected two-stage transition (from FE to SCLC) is no longer valid for FE not obeying the traditional Fowler-Nordheim (FN) law. By employing a generalized FN scaling of $\mathrm{ln}(J/{E}_{s}^{k})\ensuremath{\propto}\ensuremath{-}1/{E}_{s}$, where ${E}_{s}$ is the surface electric field at the cathode, we show the existence of a critical exponent ${k}_{c}\ensuremath{\equiv}3/2$ where unusual behaviors occur for $k<{k}_{c}$: (a) only FE at small $D$ (no transition to SCLC possible) and (b) three-stage transition from FE first to SCLC then back to FE at large $D$. For $k>{k}_{c}$, the conventional two-stage transition from FE to SCLC will always occur for all $D$, including the classical case of $k$ = 2. Using various unconventional FE models with $k\ensuremath{\ne}\phantom{\rule{0.2em}{0ex}}2$, we specifically demonstrate these peculiar transitions. Under a normalized model, our findings uncover the rich interplay between the source-limited FE and bulk-limited SCLC over a wide range of operating conditions.

Electronic Parameters of Diode Based Organometallic Semiconductor Dyes Centered Ruthenium Complexes with Active COOH Terminals.

In this study, the ruthenium complexes, which is an organometallic N-3 and C-106 semiconductor material, was coated on indium tin oxide (ITO) by using the self-assembled technique and thus a diode containing an organometallic interface was produced. The effects of this interface on the electronic parameters of the diode were investigated. It is aimed to improve the heterogeneity problem of the inorganic/organic interface by chemically bonding these materials from COOH active parts to the ITO surface. In order to understand how the electronic parameters of the diode change with this modification, the Schottky diode electrical characterization approach has been used. The charge mobility of the diode was calculated using the current density-voltage curve (J-V) characteristic with Space Charge Limited Current (SCLC) technique. When the electrical field is applied to the diode, it can be said that the ruthenium complexes molecules create an electrical dipole and the tunneling current is transferred to the anode contact ITO through the ruthenium molecule through the charge carrier, thus contributing to the hole injection. The morphology of these interface modifications was examined by Atomic Force Microscope (AFM) and surface potential energy by KelvinProbe Force Microscope (KPFM). To investigate local conductivity of bare ITO and modified ITO surface, Scanning Spreading Resistance Microscopy (SSRM) that is a conductive AFM analyzing technique were performed by applying voltage to the conductive tip and to the sample. According to the results of this work the diode containing N-3 material shows the best performance in terms of charge injection to the ITO due to possess the lowest barrier height Φb as 0.43 eV.

A multi-dimensional Child–Langmuir law for any diode geometry

While prior theoretical studies of multi-dimensional space-charge limited current (SCLC) assumed emission from a small patch on infinite electrodes, none have considered emission from an entire finite electrode. In this paper, we apply variational calculus (VC) and conformal mapping, which have previously been used to derive analytic solutions for SCLC density (SCLCD) for nonplanar one-dimensional geometries, to obtain mathematical relationships for any multi-dimensional macroscopic diode with finite cathode and anode. We first derive a universal mathematical relationship between space-charge limited potential and vacuum potential for any diode and apply this technique to determine SCLCD for an eccentric spherical diode. We then apply VC and the Schwartz–Christoffel transformation to derive an exact equation for SCLCD in a general two-dimensional planar geometry with emission from a finite emitter. Particle-in-cell simulations using VSim agreed within 4%–13% for a range of ratios of emitter width to gap distance using the thinnest electrodes practical for the memory constraints of our hardware, with the difference partially attributed to the theory's assumption of infinitesimally thin electrodes. After generalizing this approach to determine SCLCD for any orthogonal diode as a function of only the vacuum capacitance and vacuum potential, we derive an analytical formulation of the three-dimensional Child–Langmuir law for finite parallel rectangular and disk geometries. These results demonstrate the utility for calculating SCLCD for any diode geometry using vacuum capacitance and vacuum potential, which are readily obtainable for many diode geometries, to guide experiment and simulation development.

Switching characteristic of fabricated nonvolatile bipolar resistive switching memory (ReRAM) using PEDOT: PSS/GO

In this study, a bipolar resistive switching random access memory cell (ReRAM) by blending PEDOT: PSS into Graphene Oxide (GO) with 1:1 wt% is reported. To compare the switching mechanism, the memory devices based on GO and PEDOT: PSS are distinctly fabricated and characterized too. The spin coated active layers are sandwiched between ITO and Al as the bottom and top electrodes, respectively. The resistive switching mechanism in PEDOT: PSS/GO memory is based on filamentary type. The SET and RESET operation of the PEDOT: PSS/GO memory is relatively symmetric but GO and PEDOT: PSS samples have a significant asymmetric hysteresis curve. The carrier transport mechanism of the bistable behaviour for the fabricated non-volatile ReRAM is described based on space charge limited current (SCLC). In our experiments, the structure ITO/PEDOT:PSS-GO/Al demonstrated good switching behaviour with approximately 100 on/off current ratio, 3.5 V set/reset voltage and, a high retention time of 6000 s. In addition, the crystallinity and surface topography of the deposited thin film was characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The simple structure and low-cost fabrication offer embedding in data storage and computing application as future electronics and printed electronics.

Incorporating photoemission into the theoretical unification of electron emission and space-charge limited current

Photon emitters are becoming increasingly important due to their ability to generate high brightness, low emittance, and spatiotemporally coherent electron bunches for multiple applications; however, these emitters rarely produce electrons solely due to photoemission. Often, photon emitters are prone to undesired thermionic emission; alternatively, some devices intentionally leverage field and thermionic emission to increase output current. Regardless, attempting to extract higher currents from these devices raises concerns about space-charge buildup. While theories have examined the transitions between many of these mechanisms, none have used a common framework to unify photo-, thermionic, field, and space-charge limited emission simultaneously, typically represented individually by the Fowler–Dubridge (FD), Richardson–Laue–Dushman (RLD), Fowler–Nordheim (FN), and Child–Langmuir (CL) equations, respectively. This paper derives an exact solution unifying these mechanisms and reports conditions where emission bypasses RLD to directly transition from FD to FN based on asymptotically matching the three models at a nexus point. Furthermore, we provide a step-by-step approach for developing nexus phase space plots exhibiting the operating conditions for transitions among FD, RLD, FN, CL, Mott–Gurney for space-charge limited current with collisions, and Ohm's law for an external resistor. We demonstrate the utility of nexus plots for assessing the applicability of the simple well-known theories based on a single mechanism or the necessity to use more complicated solutions combining multiple mechanisms. As such, nexus theory provides a simple framework for guiding theorists in model development, simulation experts in algorithm development and selection, and experimentalists in device design.

Insight into the Role of Guanidinium and Cesium in Triple Cation Lead Halide Perovskites

The overall impact of the partial replacement (5–15%) of methylammonium (MA) in the MAPbI3 perovskite by cesium or guanidinium (Gua) cations to fabricate thin films of triple cation Cs x Gua y MA1–x–y PbI3 perovskites is studied. The structural changes are investigated by using X‐ray diffraction measurements revealing shrinkage or expansion of the unit cell upon Cs or Gua incorporation, respectively. The optoelectronic properties are characterized with photoluminescence (PL) time‐resolved spectroscopy and the space charge limited current (SCLC) method. Shorter PL time constants are obtained for the samples with only Cs, while longer PL decays are measured for the perovskites containing additional Gua cation. The SCLC measurements reveal a larger density of trap states in the Cs x MA1–x PbI3 perovskites compared to the MAPbI3 material. The PSCs fabricated with the different mixed cation Cs x Gua y MA1–x–y PbI3 perovskites reveal a good correlation with the measured optoelectronic properties. The power conversion efficiency (PCE) improves from an average value of 18.6% for the MAPbI3 to a value of 20.0% for the Cs0.05Gua0.05MA0.90PbI3 perovskite with a champion cell delivering 21.2%. On the opposite, the PCE decreases to a value of 17.3% for the double cation perovskite with Cs.

The effect of calcination temperature on the photophysical and mechanical properties of copper iodide (5 mol%)–doped hydroxyapatite

Nanocomposite consisting of 5 mol% crystalline CuI-doped hydroxyapatite (HA) was prepared for the first time by facile chemical method and calcined at different temperatures such as 300 °C, 500 °C, 700 °C and 900 °C. In this study, HA played a role as the matrix and CuI was the reinforcement. The effect of calcination temperature on XRD pattern, TEM, SEM, BET, FTIR, luminescence intensity, photoluminescence quantum yield (PLQY), fluorescence lifetime, charge mobility measurements, electronic speckle pattern interferometry and mechanical properties were investigated. The modified Scherrer equation of the composites showed that the size of the particles increased with increasing calcination temperature from 66.64 to 87.20 nm. The photoluminescence intensity of CuI (5 mol%)/HA was quenched at room temperature, while the represented constant decay time for the calcined compound was increased at 700 °C. Furthermore, the CIE coordinates were shown 0.39333, 0.18493 for CuI (5 mol%)/HA calcined at 700 °C. The charge mobility values of the nanocomposites were extracted by space-charge limited current (SCLC) method and the range of effective mobility was from 3.645 × 10−4 to 6.697 × 10−4 cm2V−1s−1. Mechanical properties were fully discussed via ASTM-E9 standard and CuI (5 mol%)/HA calcined at 900 °C was in better range than other compounds, the σyc and hardness values were reported 7.32 Mpa and 40.81 HV respectively. Speckle interferometry was used to demonstrate that there was no large imperfection in the surface of each sample. The components were very sensitive to the calcination temperatures. In other words, the combination of CuI (5 mol%)/HA showed that the replacement of Cu ions with Ca was helpful to improve the photophysical and mechanical properties.

Effect of RF Power on the Physical Properties of Sputtered ZnSe Nanostructured Thin Films for Photovoltaic Applications.

Zinc selenide (ZnSe) thin films were deposited by RF magnetron sputtering in specific conditions, onto optical glass substrates, at different RF plasma power. The prepared ZnSe layers were afterwards subjected to a series of structural, morphological, optical and electrical characterizations. The obtained results pointed out the optimal sputtering conditions to obtain ZnSe films of excellent quality, especially in terms of better optical properties, lower superficial roughness, reduced micro-strain and a band gap value closer to the one reported for the ZnSe bulk semiconducting material. Electrical characterization were afterwards carried out by measuring the current–voltage (I-V) characteristics at room temperature, of prepared “sandwich”-like Au/ZnSe/Au structures. The analysis of I-V characteristics have shown that at low injection levels there is an Ohmic conduction, followed at high injection levels, after a well-defined transition voltage, by a Space Charge Limited Current (SCLC) in the presence of an exponential trap distribution in the band gap of the ZnSe thin films. The results obtained from all the characterization techniques presented, demonstrated thus the potential of ZnSe thin films sputtered under optimized RF plasma conditions, to be used as alternative environmentally-friendly Cd-free window layers within photovoltaic cells manufacturing.

Excellent Bipolar Resistive Switching Characteristics of Bi4Ti3O12 Thin Films Prepared via Sol-Gel Process.

Herein, Bi4Ti3O12 (BIT) ferroelectric thin films were fabricated into Au/BIT/LaNiO3/Si structures to demonstrate their memristor properties. Repeatable and stable bipolar resistive switching (RS) characteristics of the device are first reported in this work. The switching ratio of the device annealed in air reached approximately 102 at 0.1 and −0.1 V. The RS performance was not significantly degraded after 100 consecutive cycles of testing. We also explored the factors affecting the RS behavior of the device. By investigating the RS characteristics of the devices annealed in O2, and in combination with XPS analysis, we found that the RS properties were closely related to the presence of oxygen vacancies. The devices annealed in air exhibited a markedly improved RS effect over those annealed in O2. According to the slope fitting, the conduction mechanism of the device was the ohmic conduction and space charge limited current (SCLC). This study is the first to successfully apply BIT ferroelectric films to the RS layers of memristors. Additionally, a theory of conductive filaments is proposed to adequately explain the relationship between RS behavior and oxygen vacancies, providing meaningful inspiration for designing high-quality resistive random access memory devices.

Optical properties and current conduction in annealed (Ta2O5)0.94 – (TiO2)0.06 thin films

By sputtering the mosaic assembly of tantalum (Ta) and titanium (Ti) metal targets in the oxygen environment, (Ta2O5)1−x–(TiO2)x, x = 0.06, thin films were deposited onto the quartz, and P/boron-silicon (1 0 0) substrates, at room temperature (RT). The RT deposited films were annealed for 1.5 h, from 500 to 800 °C. Formation of the crystal structure in the films was observed at and above 700 °C annealing. Optical transmittance data, measured with the UV–Vis spectrophotometer, were used to find out the extinction coefficient (k), refractive index (nopt), and optical bandgap (Eg) of the prepared films. With the increasing annealing temperature, both the nopt and Eg values were observed, decreasing from 2.218 to 2.160, and 4.23 to 4.02 eV, respectively. The extinction coefficient of amorphous films was observed lesser than the crystalline films. The current–voltage characteristics of the prepared film assisted metal–oxide–semiconductor (MOS) structures manifest different conductions, viz., ohmic at the lower electric fields; and Schottky, Poole–Frenkel, Fowler–Nordheim tunneling and space–charge–limited current, in the intermediate to higher fields, for different annealing treatments.

Comparative Study on the Separate Extraction of Interface and Bulk Trap Densities in Indium Gallium Zinc Oxide Thin-Film Transistors Using Capacitance–Voltage and Current–Voltage Characteristics

The interface and bulk trap densities were separately extracted from self-aligned top-gate (SA-TG) coplanar indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) using the low-frequency capacitance–voltage (C–V) characteristics and space-charge-limited current (SCLC) under the flat-band condition. In the method based on the C–V curve, the energy distribution of the interface trap density was extracted using the low-frequency C–V characteristics, and that of the bulk trap density was obtained by subtracting the density of interface trap states from the total subgap density of states (DOS) at each energy level. In the SCLC-based method, the energy distribution of the bulk trap density was extracted using the SCLC under the flat-band condition at high drain-to-source voltages, and that of the interface trap density was obtained by subtracting the density of bulk trap components from the total subgap DOS at each energy level. In our experiments, the two characterization techniques provided very similar interface and bulk trap densities and showed that approximately 60% of the subgap states originate from the IGZO/SiO2 interface at the conduction band edge in the fabricated IGZO TFTs, although the two characterization techniques are based on different measurement data. The results of this study confirm the validity of the characterization techniques proposed to separately extract the interface and bulk trap densities in IGZO TFTs. Furthermore, these results show that it is important to reduce the density of interface trap states to improve the electrical performance and stability of fabricated SA-TG coplanar IGZO TFTs.

Universal electron transporting layers via mixing two homostructure molecules with different polarities for organic light-emitting diodes

In general, electron transport layer (ETL) in organic light-emtting diodes (OLEDs) consists of single component of electron transporting material (ETM) or a mixture with n-dopant such as 8-hydroxyquinolinolato-lithium (Liq). However, there exists a limit to controlling a wide range of carrier density in OLEDs according to the required characteristics of the devices due to electrically insulating property of Liq. Here, we suggest a universal strategy to construct an efficient ETL. We synthesized two ETMs, diphenyl-[4-(10-phenyl-anthracene-9-yl)-phenyl]-amine (An-Ph) and phneyl-[4-(10-phenyl-anthracene-9-yl)-phenyl]-pyridin-3-yl-amine (An-Py) that have the same core structures with different polarities in functional groups. The electrical characteristics of electron-only-devices (EODs) were investigated by space charge limited current (SCLC) modeling and impedance spectroscopy analysis. Interestingly, the homostructure type ETL composed of An-Ph and An-Py showed not only superior electron transporting capability, but also the possibility of controlling electron injection and transporting in a wide range compared to the heterostructure type ETL of An-Ph and Liq. Compared to the An-Ph-only EOD, the electron mobility in 75% An-Py-mixed homostructure EOD increased by almost 4 orders of magnitude. Such dramatic variation of electron mobility was achieved thanks to the molecular design strategy to separate charge injection and charge transport regions within a molecule, which consequently induced the giant surface potential (GSP) effect between the ETL/cathode interface. As a result, the external quantum efficiency (EQE) of blue fluorescent and phosphorescent OLEDs with the homostructure ETLs was enhanced by 28.6% and 34%, respectively, compared to that of each control device without manipulating outcoupling effects. • The anthracene-based electron transporting materials, An-Py and An-Ph with different polarities were designed and synthesized for universal electron transporting layers. • The superior charge injection property was comprehensively investigated with impedance spectroscopy and attributed to the giant surface potential in the ETL. • Compared to Liq-based ETL, the EQE of fluorescent and phosphorescent OLEDs with An-Py and An-Ph ETL was enhanced by 28.6% and 34%, respectively.

Pyrenesulfonic Acid Sodium Salt for Effective Bottom‐Surface Passivation to Attain High Performance of Perovskite Solar Cells

In perovskite solar cells, not only defects on the top perovskite film surface seriously affect device performance, those buried in the bottom perovskite–electron‐transfer layer (ETL) interface damage carrier extraction, transport, and device efficiency as well. Herein, a novel double‐sided passivation strategy is designed using a single π‐conjugation‐induced 1‐pyrenesulfonic acid sodium salt (PyNa+). It is found that it effectively passivates top and bottom interface defects to render high device performance. The π‐conjugated pyrene‐containing sodium salt electronically contributes to the surface band edges and influences the carrier dynamics by passivating defects at both top hole‐transfer layer (HTL)–perovskite and bottom perovskite–ETL interfaces. The density functional theory (DFT) calculation confirms that the Pb cluster and I—Pb antisite defects can be effectively passivated by the O···Pb coordination and electrostatic interaction of PyNa+. The carrier lifetimes are prolonged, the interface defect density is effectively reduced as measured by space‐charge‐limited current (SCLC). Through the double layer passivation of PyNa+, the device delivers improved power conversion efficiencies of 21.22% relative to that of a reference perovskite, and enhanced stability with 85% of original efficiency after 1440 h in atmospheric environment. Double‐sided passivation provides a comprehensive strategy for high‐performance perovskite solar cells.

Mechanochromic and thermally activated delayed fluorescence dyes obtained from D–A–D′ type, consisted of xanthen and carbazole derivatives as an emitter layer in organic light emitting diodes

In this study, we designed, engineered and investigated two new thermally activated delayed fluorescence (TADF) dyes obtained from D–A–D′ type, consisted of 2-(9H-carbazol-9-yl)-3-(3-methoxy-9H-carbazol-9-yl)-9H-xanthen and 2-(3,6-di-tert-butyl-9H-carbazol-9-yl)-3-(3-methoxy -9H-carbazol-9-yl)-9H-xanthen. In these dyes, xanthen derivative and carbazole derivatives have played important roles as an acceptor and two unsymmetrical donor units. In addition, the photophysical properties of these dyes were evaluated by the UV–VIS absorption, photoluminescence spectroscopy and photoluminescence decay lifetime analysis in solution, initial dye, non-doped and doped solid state (neat–film) at different temperatures and under the vacuum-ambient. Substitution's strong effect of the donor units was impressive; where, the dyes' ionization potential values were achieved as 5.53 and 5.62 eV. The charge mobility measurements of dyes were carried out using two different methods of spacecharge–limited current (SCLC) and time of the flight (TOF). Appropriate extracted results proved dyes' promising application as an emitter layer in organic light emitting diodes (OLEDs), through the photophysical properties, aggregation induced emission enhancement (AIEE) phenomenon, and high intensity of emission spectrum spanning the large part of visible area and good thermal stability. The solution process and physical evaporation deposition (PVD) procedure were tandemly performed in order to coat the layers and fabricate non-doped and doped OLEDs. The low turned on voltage' values of OLEDs were recorded in the range of 4.08 to 5.31 V. Furthermore, the maximum values of brightness, current, power and external quantum efficiency were achieved as 72565 cd/m2, 37.32 cd/A, 20.99 lm/W and 13.41%, respectively.

Electrical conductivity of 1,3-bis(N-carbazolyl)benzene (mCP) on a hole-transport bilayer

We studied the electrical conductivity of a bilayer specimen of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidine (α-NPD) and 1,3-bis(N-carbazolyl) benzene (mCP). The conductivity of indium tin oxide ITO/(heptadecafluoro-1,1,2,2-tetrahydrodecyl)triethoxysilane (FSAM)/α-NPD(50 nm)/Al can be explained by the space-charge-limited current (SCLC) model. In an α-NPD(50 nm)/mCP(10 nm) specimen, the current is similar to that in an α-NPD(50 nm) specimen despite the existence of a hole barrier between the α-NPD and mCP. The current in an α-NPD/mCP specimen is also proportional to the square of the voltage. We propose a conduction model that combines SCLC in the α-NPD layer and tunneling in the mCP layer.

1,10-Phenanthroline as an Efficient Bifunctional Passivating Agent for MAPbI3 Perovskite Solar Cells.

Passivation is one of the most promising concepts to heal defects created at the surface and grain boundaries of polycrystalline perovskite thin films, which significantly deteriorate the photovoltaic performance and stability of corresponding devices. Here, 1,10-phenanthroline, known as a bidentate chelating ligand, is implemented between the methylammonium lead iodide (MAPbI3) film and the hole-transport layer for both passivating the lead-based surface defects (undercoordinated lead ions) and converting the excess/unreacted lead iodide (PbI2) buried at interfaces, which is problematic for the long-term stability, into "neutralized" and beneficial species (PbI2(1,10-phen)x, x = 1, 2) for efficient hole transfer at the modified interface. The defect healing ability of 1,10-phenanthroline is verified with a set of complementary techniques including photoluminescence (steady-state and time-resolved), space-charge-limited current (SCLC) measurements, light intensity dependent JV measurements, and Fourier-transform photocurrent spectroscopy (FTPS). In addition to these analytical methods, we employ advanced X-ray scattering techniques, nano-Fourier transform infrared (nano-FTIR) spectroscopy, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to further analyze the structure and chemical composition at the perovskite surface after treatment at nanoscale spatial resolution. On the basis of our experimental results, we conclude that 1,10-phenanthroline treatment induces the formation of different morphologies with distinct chemical compositions on the surface of the perovskite film such that surface defects are effectively passivated, and excess/unreacted PbI2 is converted into beneficial complex species at the modified interface. As a result, an improved power conversion efficiency (20.16%) and significantly more stable unencapsulated perovskite solar cells are obtained with the 1,10-phenanthroline treatment compared to the MAPbI3 reference device (18.03%).

Cerium and zinc co-doped nickel oxide hole transport layers for gamma-butyrolactone based ambient air fabrication of CH3NH3PbI3 perovskite solar cells

Cerium and zinc co-doped nickel oxide (NiOx) hole transporter layers (HTLs) developed for boosting the efficiency and stability of inverted methylammonium lead tri-iodide (CH3NH3PbI3) based glove box-free fabricated solar cells. Combining our humidity resistive gamma butyrolactone-based perovskite deposition route with an optimum doping ratio of NiOx:Zn-Ce (18:6 mmol %) layers, power conversion efficiencies boosted from 10.04% to 14.47% and stability is increased under aging conditions. This performance enhancement was questioned over NiOx layers, quality of perovskite layer and the interface between charge transport layers and perovskite. Zn doping increased the electrical conductivity while incorporation of Ce created a positive impact on surface morphology and interface quality by a decreased roughness compared to the only Zn doped layers. The work function, hole mobility and concentration were found to increase with co-doping. Besides, the trap density of the perovskite layer is lessened, hindering unfavorable charge recombination confirmed by space charge limited current (SCLC) and photoluminescence (PL) analysis.

Coexistence of memory and threshold switching behaviors in natural milk-based organic memristor

Natural biomaterials have attracted great interest for the fabrication of biocompatible memristors. Here, dense and smooth milk films were deposited on the Pt/SiO2/Si substrate by spin-coating method and resistive switching (RS) devices based milk films with the configuration of Ag/milk/Pt/SiO2/Si are fabricated for the first time. Furthermore, memory RS (MRS) and threshold RS (TRS) effects coexist in the devices, which can be controlled by appropriately setting the compliance current (I cc). The current conduction mechanisms of the devices with MRS and TRS effects are controlled by typical trap-controlled space charge limited current (SCLC) conduction and filamentary conduction mechanism. The good RS performances of the milk-based devices make them promising for sustainable bioelectronics and novel logic device applications.

Investigation of Schottky emission and space charge limited current (SCLC) in Au/SnO2/n-Si Schottky diode with gamma-ray irradiation

Investigation of Schottky emission and space charge limited current (SCLC) in Au/SnO2/n-Si Schottky diode with gamma-ray irradiation