P-type Films Research Articles

Ultrafast Electron and Hole Transfer and Efficient Charge Separation in a Sb2Se3/CdS Thin Film p-n Heterojunction.

Harvesting solar energy for different applications requires the continuous development of new semiconducting materials to exploit a broad part of the solar spectrum. In this direction, antimony selenide (Sb2Se3) has attracted a tremendous amount of attention over the past few years as a light-harvesting material for photovoltaic device applications owing to its phase stability, high absorption coefficient, earth abundance, and low toxicity. Here, we have fabricated a high-quality heterojunction of a p-type Sb2Se3 film and an n-type CdS film using the thermal evaporation technique. The photocurrent of the heterosystem was significantly higher than that of the pristine materials. This optoelectronic response was investigated using femtosecond transient absorption (TA) spectroscopy. TA study reveals the existence of an instantaneous electron transfer from Sb2Se3 to CdS, accompanied by a substantial charge separation at the heterojunction. Our study deals with the investigation of a well-designed p-n device, paving the way for the fabrication of highly efficient photovoltaic devices.

Influence of pH value of precursor on growth, structural, and optical properties of Cu2O thin films grown in Mist-CVD

The Cu2O thin films were prepared from copper (II) acetylacetonate (Cu(acac)2) by the mist chemical vapor deposition (mist-CVD) method, depending on the pH value of the prepared solution. It was confirmed that the well-oriented Cu2O thin films were grown at a dominant (111) peak according to X-ray diffraction (XRD) measurement using an alkaline precursor solution. The pH of the prepared solution drastically affected the surface morphology of the Cu2O thin films, and the lowest Root Means Square (RMS) was found for pH-10 of the precursor solution. The confocal Raman spectrum confirmed the formation of the cubic Cu2O crystal structures for each pH value of the precursor solution. The very transparent Cu2O thin films that were grown. The highest transmittance, 70%, was obtained at 1100 nm from the absorption spectrum for Sample B. The optical energy band gaps of Cu2O thin films were determined using Tauc's method and found to vary within a range of 2.53 to 2.49 eV, indicating a change in the material's electronic structure. The study demonstrated the crucial role of the pH level of the prepared solution in the growth of the Cu2O thin film. Specifically, it was found that a higher pH level resulted in a greater concentration of hydroxide ions (OH−), which was a crucial factor in the growth process. These findings can be significant in using p-type Cu2O thin films prepared based on mist-CVD for optoelectronic applications.

Vertically designed high-performance and flexible thermoelectric generator based on optimized PEDOT:PSS/SWCNTs composite films

To solve the long-lasting challenge of low thermoelectric performance of flexible thermoelectric device (F-TEG), in this work, we report a three-dimensional vertically structured F-TEG composed of flexible, stable, and high-performing p- and n-type single-walled carbon nanotube (SWCNT)-based composite films. The p-type SWCNT-based composite film exhibits a high room-temperature power factor of >500 μW m−1 K−2, benefiting from the effective de-doping of the hybridized poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) (PEDOT:PSS) using a binary co-doping agent composed of NaHCO3 and the polar solvent ethylene glycol (EG). Simultaneously, the n-type SWCNT-based film doped with the amine-rich electron donor polyethyleneimine (PEI) is prepared, exhibiting a high room-temperature power factor of 185.4 μW m−1 K−2 and excellent air stability. By employing flexible supporting foam, vertical p-n thermoelectric legs are realized, and the F-TEG based on these legs exhibits a maximum open-circuit voltage of 23.2 mV and a maximum output power of 2.6 μW at a temperature difference of 48 K, demonstrating a competitive normalized power density of >2.5 μW cm−2 K−2, which advances the low-power flexible wearable field.

Growth of CuAlO2 on SiO2 under a layer-by-layer approach conducted by digitally processed DC sputtering and its transistor characteristics

A CuAlO2 (CAO) bottom gate top contact p-type thin film transistor (TFT) is demonstrated. The CAO thin film is synthesized through a digitally processed DC sputtering (DPDS) technique, employing a precise layer-by-layer (LBL) deposition strategy. X-ray diffraction analysis exhibited distinct peaks beyond 600 °C. The CAO film shows a dominant phase along the (004) plane at the elevated temperature of 990 °C. The fabricated CAO p-TFT exhibits field effect mobility of 4.1 cm2 V−1 s−1. In addition, the p-TFT characteristics were observed even in the as-deposited CAO film. The DPDS-assisted LBL approach offers a promising pathway for controlled stacking deposition routes in the growth of CAO thin films, enabling enhanced performance and device integration.

Fabrication and Electrical Characterization of p/n PbSe Diodes

Lead selenide (PbSe) diodes were fabricated using a magnetron sputtering process system with a pulsed DC power supply and a 2-inch PbSe target with a purity of 5N. For p-type PbSe thin films, the process variable was the oxygen ratio in the mixed gas of argon and oxygen. The electrical characteristics of the thin films were observed after heat treatment. For the n-type PbSe, nickel (Ni) was used as a doping material. The deposition and doping were performed simultaneously using a co-sputtering method. During co-sputtering, the input power of the Ni sputter gun was adjusted as a process variable. Hall measurement experiments were performed to measure the doping concentration and resistivity of both the p-type and n-type PbSe semiconducting films. The maximum doping concentration was 2.33×10<sup>19</sup> cm<sup>-3</sup> for p-type PbSe and 7.55×10<sup>20</sup> cm<sup>-3</sup> for n-type PbSe thin films, respectively. The p-n junction IV curve showed that the lowest forward voltage generation point, V<sub>f</sub>, was 1.5 V and the reverse breakdown voltage was -4.3 V. In the photocurrent measurement, the photo sensitivities of the heat-treated samples were higher than that of the non-treated sample, and the maximum value was 5.148. Photo responsivity was also higher in the heat-treated samples. Its maximum was 0.7306 mA / W.

High-performance p-type V2O3 films by spray pyrolysis for transparent conducting oxide applications.

High-quality epitaxial p-type V2O3 thin films have been synthesized by spray pyrolysis. The films exhibited excellent electrical performance, with measurable mobility and high carrier concentration. The conductivity of the films varied between 115 and 1079 Scm-1 while the optical transparency of the films ranged from 32 to 65% in the visible region. The observed limitations in thinner films' mobility were attributed to the nanosized granular structure and the presence of two preferred growth orientations. The 60nm thick V2O3 film demonstrated a highly competitive transparency-conductivity figure of merit compared to the state-of-the-art.

Super high-speed self-powered photodetector based on solution-processed transparent p-type amorphous phosphorous-doped SnO film

Super high-speed self-powered photodetector based on solution-processed transparent p-type amorphous phosphorous-doped SnO film

Synaptic plasticity and memory mimicked in solution-processed K-doped CuI thin film transistors

Low-voltage electric double layer p-type thin film transistors (TFTs) were fabricated on glass substrates with copper iodide doped with potassium iodide (Cu0.95K0.05Ix) as the channel and chitosan as the dielectric. Cu0.95K0.05Ix TFTs exhibited Ion/Ioff ratio of 2.5 × 104, subthreshold swing of 30 mV/dec, threshold voltage of 1.34 V, operating voltage of 2 V, and saturation field-effect mobility of 16.6 cm2 V−1 s−1. The relaxation phenomenon induced by ion migration was effectively utilized, enabling Cu0.95K0.05Ix TFTs to simulate various synaptic plasticity functions. When a pulse is applied, the drain current reaches a peak, but it takes more time for the current to return to its equilibrium position after the pulse is removed, demonstrating the short-term memory (STM) characteristics of Cu0.95K0.05Ix TFT. It was observed an increasing trend in excitatory postsynaptic current (EPSC) with enhanced pulse width and amplitude, and when the pulse amplitude increased to −10 V, the TFT transitioned from STM to long-term memory characteristics. Furthermore, the measurement of consecutive EPSC revealed the paired-pulse facilitation (PPF) characteristics, with a gradual decrease in the PPF coefficient as the time interval increased, and a selective stronger response to high-frequency signals. Based on the aforementioned research, by extending the device structure to a dual in-plane-gate structure configuration and applying different pulse voltage sequences on the dual gate, the NOR logic functionality was achieved. The study demonstrates the significant potential of p-type Cu0.95K0.05Ix TFTs in the field of synaptic bionics, simulating human learning and memory, and neural chips.

CuO thin films deposited by the dip-coating method as acetone vapor sensors: Effect of their thickness and precursor solution molarity

The superficial morphology and porosity of metal oxide films play an important role in their sensing response to the presence of organic vapors. For films deposited from precursor solutions, both can be modified by varying the solution's molarity and thickness; however, their effect on the film's sensitivity has been scarcely studied in p-type materials. In this work, CuO p-type nanostructured films on glass substrates were obtained from three precursor solutions at different molarities. The films were deposited by dip-coating, varying the coats to obtain thicknesses in the 100–1700 nm wide range. Scanning electron microscopy images show surfaces with higher porous presence as the film's thickness and precursor solution molarity increase. The CuO films were tested as acetone-vapor sensors in a wide concentration range from 1 to 2000 ppm at a sample temperature Ts = 300 °C. Their sensitivity (S) grows as the film thickness increases, regardless of the solution molarity, associated with a higher porosity, calculated from refractive index values. The highest response is obtained for CuO thickest film (τ = 1670 nm) deposited from the solution at the highest molarity. S values of 1.3, 3.4, 4.75, and 7.4 are obtained at 1, 100, 300, and 2000 ppm acetone-vapor concentrations, respectively. These S values are inside the reported ones using more sophisticated techniques and processes.

Communication—Annealing Strategies for Spray Deposited Precursor Films of p-Type CuCr1-xMgxO2

Annealing of sprayed pure and Mg doped CuCrO2 thin films by high intensity, short time light irradiation leads to a single delafossite phase at comparatively low temperatures compared with traditional furnace annealing. P-type crystalline undoped and Mg-doped CuCrO2 films were obtained within few minutes by annealing with halogen lamp between 550 °C and 650 °C in Ar atmosphere. Transport properties of Mg-doped thin films were comparable to furnace annealed samples despite much shorter annealing time. The results demonstrate that post-annealing of chemically deposited samples using light irradiation is an effective and fast method for obtaining transparent conducting delafossite thin films.

A facile in-situ reaction method for preparing flexible Sb2Te3 thermoelectric thin films

Inorganic p-type Sb2Te3 flexible thin films (f-TFs) with eco-friendly and high thermoelectric performance have attracted wide research interest and potential for commercial applications. This study employs a facile in-situ reaction method to prepare flexible Sb2Te3 thin films by rationally adjusting the synthesized temperature. The prepared thin films show good crystallinity, which enhances the electrical conductivity of ~1,440 S·cm-1 due to the weakened carrier scattering. Simultaneously, the optimized carrier concentration, through adjusting the synthesis temperature, causes the intermediate Seebeck coefficient. Consequently, a high-power factor (16.0 μW·cm-1·K-2 at 300 K) is achieved for Sb2Te3 f-TFs prepared at 623 K. Besides, the f-TFs also exhibit good flexibility due to the slight change in resistance after bending. This study specifies that the in-situ reaction method is an effective route to prepare Sb2Te3 f-TFs with high thermoelectric performance.

Unveiling the nature of room-temperature-fabricated p-type SnO thin films: the critical role of intermediate phases, lattice disorder, and oxygen interstitials

This study showcases the use of ion-beam-assisted deposition for fabricating p-type SnO thin films at room temperature, which reveals crucial links between Hall mobility and lattice disorder, and between hole concentration and the relative content of interstitial oxygen.

Inhibition of ion diffusion/migration in perovskite p-n homojunction by polyetheramine insert layer to enhance stability of perovskite solar cells with p-n homojunction structure.

Perovskite p-n homojunctions (PHJ) have been confirmed to play a crucial role in facilitating carrier separation/extraction in the perovskite absorption layer and provide an additional built-in potential, which benefits the inhibition of carrier recombination in perovskite solar cells (PSCs) and ultimately improves device performance. However, the diffusion and migration of ions between n-type and p-type perovskite films, particularly under operational and heating conditions, lead to the degradation of PHJ structures and limit the long-term stability of PSCs with PHJ structure (denoted as PHJ-PSCs). In this study, we propose an insert layer strategy by directly introducing an ultra-thin polyetheramine (PEA) layer between the n-type and p-type perovskite films to address those challenges arising from ion movements. Femtosecond transient absorption (fs-TAS) and photoluminescence (PL) measurements demonstrate that the PHJ (without and with the insert layer) enhances carrier separation/extraction compared to the single n-type perovskite film. Monitoring the evolution of bromine element distribution reveals that the insert layer can efficiently suppress ion diffusion between perovskite films, even under long-term illumination and heating conditions. Consequently, an efficiency of 23.53% with excellent long-term operational stability is achieved in the optimized PHJ-PSC with the insert layer.

N-type and P-type SnOx thin films based MOX gas sensor testing

N-type and P-type SnOx thin films based MOX gas sensor testing

High Current Stress Analysis for p-type LTPS Thin Film Transistor with Split Active Layer for High Current Driving AMOLED Display

High Current Stress Analysis for p-type LTPS Thin Film Transistor with Split Active Layer for High Current Driving AMOLED Display

Development, experimental and simulated performance of copper iodide (γ-CuI) uni-track thin film thermoelectric modules

In this article, we investigate the performance of 950 nm thick p-type γ-CuI uni-track thin film thermoelectric modules. A model was first developed to optimize a module’s geometry, focusing on the length and the number of the γ-CuI tracks. Based on the maximum power achieved and the open circuit voltage (above 225 mV), the simulation optimized module consists of three tracks of γ-CuI, each with a length of 13 mm. Using these simulation results, modules were elaborated through solid iodination process of Cu thin tracks. These γ-CuI tracks were then connected with Pt electrodes. After characterizing the structure and electrical properties of the γ-CuI material, the module’s performance was measured at various applied temperatures in a free gradient mode. The results were in agreement with the simulation. Experimental and simulated performances highlight the significant impact of contact resistance as the temperature increases limiting module performances. A maximum power of 61nW was achieved at an applied temperature of 190 °C. This suggests that higher values could be attained through optimized contacts, with the goal of enabling some commercial applications for easily manufactured modules. Due to the optoelectrical properties of γ-CuI, this even paves the way for the development of new transparent thermoelectric generators.

P-Type LaCuOS films grown by PLD using a quaternary target fabricated by a two-step solid-state reaction/sulfurization process

A LaCuOS target was obtained through a two-step route: first, the synthesis of the CuLaO2 compound by solid-state reaction, and subsequently its sulfurization under a sulfur atmosphere. The LaCuOS powder was used to deposition films by pulsed laser deposition at different growth times: 10, 15, 20, and 25 min. The films were deposited in vacuum at a substrate temperature of 400 °C and a wavelength of 266 nm. The structural characterization showed that the dislocation density and stress in LaCuOS films increase as the deposition time increases. The LaCuOS films exhibit optical transmittance of 52–81 % in the visible region. Electrical measurements indicate high values of hole mobility and carrier densities up to 1019 cm−3, with a p-type electrical conductivity of 0.74 S/cm; these properties suggest that LaCuOS films have the potential to be integrated as transparent material in devices.

P-type NiOx ultrathin film as highly efficient hole extraction layer in n-type PbS quantum dots based NIR photodiode

Recently, the development of zero-dimensional (0D) materials has experienced significant growth. Among them, PbS colloidal quantum dots (CQDs) have received special attention due to their outstanding properties, including tunable optical absorption ranging from 600 to 2600 nm (size dependent bandgap) and easy solution synthesis. PbS CQDs are considered as one of the most promising materials for the next generation of infrared sensors. Hence, there is a growing interest in their use in industrial spheres. One of the major keys to obtaining high-performance devices is the realization of efficient charge extraction contacts on PbS CQDs films. In this work, we have demonstrated an efficient hole extraction layer (HEL) using NiOx ultra-thin film on infrared p-i-n photodiode based on only n-type PbS nanocrystals (CQDs). We compared the performance with the standard optimized MoOx. We obtained a significant gain in external quantum efficiency (EQE), a decrease of the operating bias, while keeping the same dark current level.

CO2 reduction by visible-light-induced photoemission from heavily N-doped diamond nano-layer

While realizing carbon neutrality is an urgent priority, diamond materials with negative electron affinity (NEA) are considered productive sources of solvated electrons, which can help efficiently reduce CO2 in potential green chemistry applications. Recently, CO2 was photocatalytically reduced into CO by solvated electrons using commonly used H-terminated diamond with NEA under deep ultraviolet light irradiation. However, CO2 has never been reduced under visible-light irradiation, would be more practicable in the living environment, because of the wide band gap afforded by diamonds. In this study, electrons excited by visible light in heavily N-doped surface nano-layer of diamond platelets are emitted through the H-terminated surface with NEA toward a CO2-saturated aqueous solution, successfully reducing CO2 into CO. To this end, the B-doped p-type diamond films are grown by chemical vapor deposition on initial seed layers of detonation-synthesized nanodiamonds (DNDs). This approach allows incorporating the abundantly available N atoms in the DNDs into the surface nano-layer on the diamond platelets, resulting in the formation of an electron-excitation nano-layer having ≥1021 N atoms/cm3 and associated defects absorbing visible light. These results pave the way toward a new, energy-efficient technology for CO2 reduction with strong implications for achieving a carbon-negative society.

High thermoelectric performance of n-type Mg3Bi2 films deposited by magnetron sputtering

Mg3Bi2 are of great interest for thermoelectric applications near room temperature. In this paper, A metastable cubic phase(c-Mg3Bi2) films were prepared on glass substrate using Mg and Bi elemental targets by magnetron sputtering. Investigations were done on the phase composition, microstructure and thermoelectric properties of films that were deposited with various atomic ratios of Bi to Mg. When the atomic ratio of Mg/Bi exceeded the stoichiometry of 3:2, the films displayed a metastable cubic phase (c-Mg3Bi2) with a highly (111) preferred orientation. The deposited (c-Mg3Bi2) films possess n-type conductivity characteristics with high carrier mobility. In the temperature range of 300–490 K, a state-of-the-art average PF of 3.11 μW cm−1K−2 is attained in a 23 at.% Bi film. A fully Mg3Bi2 thermoelectric device consisting of both n-type and p-type Mg3Bi2 thin films is fabricated. It demonstrates a maximum output power density of 239 μW cm−2 at a temperature difference of 20 K. This work offers an effective approach to development of thermoelectric devices based on Mg3Bi2 materials.