Thin film photodiodes (TFPD) can supplement complementary metal-oxide-semiconductor (CMOS) image sensor vision by their exotic optoelectronic properties assisted by their monolithic processability. Halide perovskites are known to show outstanding optoelectronic properties, such as large absorption coefficient, long carrier diffusion lengths, and high carrier mobility, leading to high external quantum efficiency (EQE) and fast charge transport in photodiodes (PDs), especially compared with other thin-film photodiode candidates. In this paper, high-resolution two-dimensional (2D) and three-dimensional (3D) imaging capabilities are demonstrated using perovskite photodetection material with a silicon (Si) read-out integrated circuit (ROIC). The integration of this perovskite photodiode (PePD) on the Si ROIC provides fine resolution for 2D imaging. The fast carrier transport properties of the PePD enable depth sensing of objects using the same sensor. 3D imaging is demonstrated using the proposed top-electrode controlled indirect time-of-flight (iToF) operation supported by the fast PD switching through the top common electrode of the TFPD image sensor pixel. It is expected that the PePDs on Si ROIC could mark a significant milestone for the TFPD imaging platform with their outstanding optoelectronic performance in combination with the CMOS image sensor technology, not only for conventional 2D imaging but also by enabling extensions toward 3D sensing, promising applications in automotive, augmented reality (AR), and virtual reality (VR).

All-inorganic cesium lead halide perovskites possess excellent thermal stability, a feature that renders them highly favorable for optoelectronic applications with an elevated thermal budget. Employing a coevaporation approach for their deposition holds promise for manufacturing at an industrial level, owing to improvements in device scalability and reproducibility. For unlocking the full potential of vacuum-evaporated perovskite thin films, it is crucial to delve deeper into their crystallization process, which, as a solid-state reaction, has been less investigated compared to the crystallization process of, most commonly used, solution-based methods. In this work, we employ spectroscopic ellipsometry, a nondestructive, high speed, and high accuracy characterization method, to study the real time annealing effect on thermally coevaporated CsPbI2Br thin films in a temperature range between 25 and 300 °C. We achieve this by developing a singular dynamic model that can be fitted in real time as a function of temperature, providing insights into how thermal annealing influences the perovskite film's morphology and optical constants. Based on the latter, we derive the temperature dependence of the thermo-optic coefficient and Urbach energy as well as analyze the interband transition energies via critical point analysis. We demonstrate that the γ- to β-phase transition can be identified through a pronounced shift in the bandgap energy, whereas the β- to α-phase transition can be discerned by a sharp increase in the film's roughness. We corroborate the obtained fit results with additional in- and ex situ measurements, such as in situ grazing incidence wide-angle X-ray scattering, atomic force microscopy, reflectance/transmittance, and profilometry.

Multi-layer coating systems are frequently used as anti-reflective coatings (ARCs) due to their excellent optical properties. However, these systems suffer from erosive degradation (wear) thus urgently seeking alternative ways to improve their mechanical properties while maintaining their optical response. To tackle this problem, we propose to dope multi-layer TiO2/SiO2 coatings with Zr-oxides to enhance their crystalline structure and density/compactness, as well as form Si-Zr-O bonds. For the first time, we explore the effect of Zr-oxide doping on the microstructure, optical and mechanical properties of multi-layer TiO2/SiO2 coatings with the overall aim to synergistically induce excellent optical and mechanical properties. Therefore, homogeneous 250 nm thick multi-layer TiO2/SiO2 coatings doped with Zr-oxides (different atomic concentrations) were deposited on glass substrates by magnetron sputtering. Based upon our analysis, we demonstrate that Zr-doping improves the optical and mechanical properties simultaneously. Among all ARCs, the sample annealed at 400 °C and doped with 1 at.-% Zr presented an excellent antireflection behavior and the best mechanical performance. These characteristics point towards an improved mechanical resistance (outstanding durability) and optical efficiency thus rendering them excellent candidates for the protection of the glass cover on solar panels.

The black perovskite phase of CsPbI3 is promising for optoelectronic applications; however, it is unstable under ambient conditions, transforming within minutes into an optically inactive yellow phase, a fact that has so far prevented its widespread adoption. Here we use coarse photolithography to embed a PbI2-based interfacial microstructure into otherwise-unstable CsPbI3 perovskite thin films and devices. Films fitted with a tessellating microgrid are rendered resistant to moisture-triggered decay and exhibit enhanced long-term stability of the black phase (beyond 2.5 years in a dry environment), due to increasing the phase transition energy barrier and limiting the spread of potential yellow phase formation to structurally isolated domains of the grid. This stabilizing effect is readily achieved at the device level, where unencapsulated CsPbI3 perovskite photodetectors display ambient-stable operation. These findings provide insights into the nature of phase destabilization in emerging CsPbI3 perovskite devices and demonstrate an effective stabilization procedure which is entirely orthogonal to existing approaches.

Recently inorganic-organic hybrid materials have been quickly arisen as promising dielectric candidates for their applications in the fabrication of solution-processed metal oxide thin-film transistors (TFTs). Based on this, we demonstrate a novel mixed metal oxide hybrid dielectric layer of zirconium hafnium oxide-poly (methylmethacrylate) (ZrHfO2-PMMA) thin films were effectively delivered by simple solution-process by using a low-cost spin coating process at a low temperature of 200 degrees C. To distinguish the chemical bonding states between inorganic and organic phases FTIR and XPS techniques were performed. The AFM analysis showed the hybrid thin films highly dense with low RMS roughness of around 1-nm. To investigate the dielectric properties of hybrid thin films, MIM capacitor devices were fabricated by using 90-nm thick hybrid dielectric layers exhibiting remarkably low leakage current density of 4.5 x 10(-9) A/cm(2), capacitance density of 84.5 nF/cm(2) with high dielectric constant (k) of 8.4 at 1 kHz. Further, the hybrid dielectric layer was applied as a gate dielectric for fabrication of TFTs with solution processed In2O3 as the channel layer. All solution processed In2O3 TFTs showed an excellent electrical response with electron mobility of 11.2 cm(2)/V. s, threshold voltage of 1.7 V, I(on)(/off )ratio of 10(6), and subthreshold swing of 0.58 V/dec. Therefore, our results illustrate the high potential of low-temperature solution processed ZrHfO2-PMMA hybrid thin films for future low-cost TFT applications as gate dielectric candidate.

In recent years $\beta $ -Ga 2 O 3 thin films and crystals have gained attention as excellent candidates for transparent and high-power applications due to its wide band gap (4.6 – 4.9 eV) and large breakdown field (~8 mV/cm). However, $\beta $ -Ga 2 O 3 single crystals and highly crystalline $\beta $ -Ga 2 O 3 thin films require high temperature, long processing times and, often, expensive tools that limit integration with other technologies. Amorphous Ga 2 O 3 has not been studied as intensely as $\beta $ -Ga 2 O 3 and mostly metal-semiconductor-metal (MSM) structures and diodes using this material have been reported. In this paper, we discuss a simple and economical method to fabricate thin film transistors (TFTs) based on un-doped amorphous Ga 2 O 3 thin films deposited at room temperature by magnetron sputtering. Control of the Ga 2 O 3 thin films resistivity over a wide range is demonstrated by controlling the deposition power and pressure. The TFTs show a threshold voltage ( $\text{V}_{{\mathrm {T}}}$ ) of 0.92 V, saturation mobility ( $\mu _{{\mathrm {sat}}}$ ) of 0.511 cm 2 / $\text{V}\cdot \text{s}$ and subthreshold slope (SS) of 83.62 mV/dec. More importantly, these devices have been evaluated as phototransistors, which has not been intensely studied yet. The phototransistors tested under DUV radiation exhibited a rejection ratio UV-Visible of 10 3 and responsivity of $10^{2}\text{A}$ /W ( $\text{V}_{{\mathrm {G}}} =0$ V) and 10 4 A/W ( $\text{V}_{{\mathrm {G}}} =6$ V), gain of 10 3 , specific detectivity of 10 15 Jones and a photosensitivity of 10 7 .

This work presents the development of a formulation for the synthesis of Pb1-xSnxS thin films by chemical bath deposition. The success of this formulation is due to the high miscibility between lead sulfide (PbS) and tin (II) sulfide (SnS). By adding different concentrations of a Pb2+ ions solution to a Sn2+ S2- formulation, we obtain Pb1-xSnxS films with different Pb/Sn ratio. The presence of Pb2+ in those films is confirmed by X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Structural analysis by X-ray diffraction (XDR) shows a crystalline phase change from an SnS orthorhombic structure (00.00 mmol Pb2+) to a solid solution where the orthorhombic and cubic structures coexist (30.00 mmol Pb2+), and finally reaching the formation of a cubic PbS structure. Changes in the morphology of the films are observed together with the incorporation of Pb2+ ions in the films, reducing the size of nano-flakes and becoming a more compact layer, leading to a decrease in the film thickness from 370 nm (00.00 mmol Pb2+) to 96 nm (50.00 mmol Pb2+). The decrease of the energy band gap (Eg) of the samples from 1.92 to 1.38 eV with the increase of the Pb2+ concentration is also observed, obtaining wide absorption spectra from visible to near-infrared.

Large-area compatible, solar-blind deep-ultraviolet sensors based on active pixels are demonstrated with CMOS amplifiers based on poly-Si thin-film transistors and Ga 2 O 3 thin-film photoresistors. The active pixel configuration sensor enables approximately 40X higher responsivity compared to a discrete sensor, and the CMOS inverter amplifier exhibits a gain of 210 V/V. The Ga 2 O 3 -based sensors were integrated on the same substrate depositing the films using magnetron sputtering at room temperature, ensuring its compatibility with large-area applications. The responsivity of discrete Ga 2 O 3 sensors was evaluated at different wavelengths in the deep-ultraviolet and visible ranges, and showed a maximum responsivity of 51 A/W for a wavelength of 232 nm, with a deep-ultraviolet to visible light rejection ratio of approximately 10 2 . The active pixel sensor was implemented as flame detector resulting in an output voltage signal of up to 2 V when the system was exposed to a flame under regular background illumination conditions.

Following the rapid increase of organic metal halide perovskites toward commercial application in thin-film solar cells, inorganic alternatives attracted great interest with their potential of longer device lifetime due to the stability improvement under increased temperatures and moisture ingress. Among them, cesium lead iodide (CsPbI3) has gained significant attention due to similar electronic and optical properties to methylammonium lead iodide (MAPbI(3)), with a band gap of 1.7 eV, high absorption coefficient, and large diffusion length, while also offering the advantage of being completely inorganic, providing a higher thermal stability and preventing material degradation. On a device level, however, it seems also essential to replace organic transport layers by inorganic counterparts to further prevent degradation. In addition, devices are mostly fabricated by spin coating, limiting their reproducibility and scalability; in this case, exploring all-evaporated devices allows us to improve the quality of the layers and to increase their reproducibility. In this work, we focus on the deposition of CsPbI3 by CsI and PbI2 co-evaporation. We fabricate devices with an all-inorganic, all-evaporated structure, employing NiO and TiO2 as transport layers, and evaluate these devices for both photodetector and solar cell applications. As a photodetector, low leakage current, high external quantum efficiency (EQE) and detectivity, and fast rise and decay times were obtained, while as a solar cell, acceptable efficiencies were achieved. These all-inorganic, all-evaporated devices represent one step forward toward higher stability and reproducibility while enabling large area compatibility and easier integration with other circuitry and, in future, the possible commercialization of perovskite-based technology.

Heterojunctions made of n-type cadmium sulfide (CdS) and p-type zinc telluride (ZnTe) thin films with rectifying behavior have been developed using an in situ approach based on pulsed laser deposition (PLD). The structure of the CdS and ZnTe thin films was observed by x-ray diffraction (XRD) analysis. Optical and electrical characterization of the semiconductor films and fabricated diodes is also reported herein. For this purpose, a set of CdS/ZnTe diodes was fabricated with circular gold contacts of varying diameters from 100 µm to 300 µm. The carrier concentrations of the semiconductor layers were determined using a Hall-effect measurement system, yielding values of 5.26 × 1018 cm−3 and 3.5 × 1013 cm−3 for CdS and ZnTe, respectively. Current–voltage (I–V) characteristic curves were used to observe the typical rectifier behavior over three orders of magnification. In addition, other parameters were obtained from the I–V curves, such as the density current, saturation current, series resistance, threshold voltage, and ideality factor. Also, capacitance–voltage (C–V) characteristic curves allowed the determination of the following parameters: depletion width, built-in voltage, and donor concentration. According to the results, such n-type CdS/p-type ZnTe heterojunctions with rectifying behavior could find potential applications in the development of photodetectors by modifying the difference in carrier concentration between the two materials.

Perovskite-based semiconductors, such as methylammonium and cesium lead halides (MPbX3: M = CH3NH3+ or Cs+; X = I-, Br-, or Cl-), have attracted immense attention for several applications, including radiation detection, due to their excellent electronic and optical properties.1,2,3,4,5,6 In addition, the combination of perovskites with other materials enables unique device structures. For example, robust and reliable diodes result when combined with metal oxide semiconductors. This device can be used for detection of nonionizing and ionizing radiation. In this paper, we report a unique perovskite single-crystal-based neutron detector using a heterojunction diode based on single-crystal MAPbBr3 and gallium oxide (Ga2O3) thin film. The MAPbBr3/Ga2O3 diodes demonstrate a leakage current of ∼7 × 10-10 A/mm2, an on/off ratio of ∼102, an ideality factor of 1.41, and minimal hysteresis that enables alpha particle, gamma-ray, and neutron detection at a bias as low as (-5 V). Gamma discrimination is further improved by 85% by optimizing the thickness of the perovskite single crystal. The MAPbBr3/Ga2O3 diodes also demonstrate a neutron detection efficiency of ∼3.92% when combined with a 10B neutron conversion layer.

A Ga2O3/CsPbBr3 solid-state diode for indirect neutron detection is demonstrated by Manuel Quevedo-Lopez and co-workers in article number 2000534. This is enabled by a novel solvent-free deposition method that allows CsPbBr3 films with pure CsPbBr3 perovskite phase, controlled stoichiometry and large grains.

The wide band gap and high breakdown field of beta-Ga2O3 single crystals and thin films have recently attracted considerable attention not only for high-power applications, fabricating devices such as transistors and diodes, but also for several other applications such as deep-UV (DUV) sensors, with a cutoff at similar to 280 nm, resulting in visible-blind detectors. Currently, most of the UV- and DUV-based simple metal-semiconductor-metal (MSM) systems use interdigitated electrodes, which requires high-quality, defect-free films. beta-Ga2O3 films deposited by simple methods such as magnetron sputtering are scarce, and most high-quality beta-Ga2O3 thin films have been demonstrated using pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). Herein, we show a comprehensive study to effectively control the structural, optical, and electrical properties of beta-Ga2O3 thin films deposited by sputtering. Highly oriented polycrystalline or nanocrystalline n-type beta-Ga2O3 thin films were deposited by this method and evaluated as DUV detectors using a simple MSM structure under DUV light with 254 and 232 nm wavelengths. Different structures-varying the number of fingers-are evaluated, under different light intensities and applying different electric fields. High responsivities are obtained, especially for nanocrystalline beta-Ga2O3 thin films. The high responsivity for both films is attributed to self-trapped holes resulting in an internal gain. Higher responsivity is also observed for higher electric fields, lower light intensities, and a smaller number of fingers. Rise and decay times are comparable, in the range of 11-13 and 14-15 ms, respectively. Our results indicate that sputtered beta-Ga2O3 thin films are promising for visible-blind DUV detectors. The paper also demonstrates simple strategies to control the crystallinity of sputtered beta-Ga2O3 thin films.

The majority of solid‐state radiation sensors are predominantly single crystals. However, for low‐cost and large‐area device applications, thin films are a better option. The first evidence of neutron detection using a Gallium Oxide/Cesium Lead Bromide (Ga 2 O 3 /CsPbBr 3 ) solid‐state diode enabled by an innovative close space sublimation (CSS) method that allows deposition of thick CsPbBr 3 films is demonstrated. Furthermore, indirect neutron sensing is achieved using a 10 B layer for diodes biased at voltages as low as –5 V, showing the potential for low‐power operation. The neutron response is enabled by the low leakage current (≈10 −8 A mm –2 ), rectification of ≈10 4 , capacitance as low as 15 pF, and fast response of the Ga 2 O 3 /CsPbBr 3 diode. The superior performance of the CsPbBr 3 is due to the phase purity, stoichiometry control, and large single‐grain columnar growth of the films obtained by the CSS method.

An ammonia-free chemical solution deposition formulation is employed to synthesize cobalt hydroxide thin films. The films are subsequently annealed at different temperatures to obtain cobalt oxide (Co3O4). The reaction solution is composed solely of cobalt sulfate and triethanolamine. The annealing temperature has a strong effect on the properties of thin films. X-ray diffraction shows that the films are amorphous despite the thermal treatment; the morphology for both as-deposited and annealed films are found to be homogeneous, compact, with no evident changes. X-ray photoelectron spectroscopy reveals that the as-deposited thin films are mainly composed of cobalt hydroxide. After annealing, the films transform into cobalt oxide (Co3O4) thin films. The optical spectra confirm the X-ray photoelectron spectra, due to the appearance of characteristic features of Co3O4 on both characterization methods. The energy band gap is estimated to lie between 2.1 and 3.0 eV. The resistivity of the annealed films ranges from 4.29 x 10(3) to 1.46 x 10(4) Omega.cm. Finally, with the work function and ionization energy, we propose an experimental band diagram as a function of annealing temperature, showing a p-type nature for the cobalt oxide films.

In this work the beneficial aspects of substituting CdS, the traditional heterojunction partner to CdTe, with a bi-layer of CdSe/CdS is studied and the results are discussed. The high short-circuit current in a CdTe/(CdSe/CdS) solar cell is mainly due to contribution from two factors; enhanced blue-response due to the reduction in CdTe band gap which a result of Se diffusion into CdTe film forming the ternary CdTe1-xSex at the interfacial region, and the use of a thinner CdSe layer which was possible due to the presence of a thin CdS film. A thin layer of CdS between indium-tin-oxide (ITO) and CdSe is essential to serve as a buffer layer minimizing the shunt paths at the heterojunction interface. A 10% increase in short-circuit current is observed when the CdS-alone heterojunction layer is substituted with a CdSe/CdS bi-layer. The SIMS depth profile analysis indicate that in devices using a CdSe/CdS bi-layer, the Cu diffusion from back contact into the CdTe bulk is limited significantly compared to a CdS-only device. The net carrier concentration across the absorber layer is not uniform and showed the characteristic U-shape with respect to depletion layer width. The apparent increase in carrier concentration near the back contact region is related to the Cu doping. The shallow vs. sharp curving of the NA-ND profile of the CdS-only and CdSe/CdS bi-layer devices is explained on the basis of the regulated Cu diffusion from the back contact into CdTe, which is a consequence of Se diffusion.

In this work, a solvent-free method to deposit in-situ methylammonium lead bromide (MAPbBr(3)) perovskite thin films is discussed. Spin-coating methods used for hybrid perovskite deposition typically use solvents that might remain in the films after processing, potentially causing accelerated film degradation. Furthermore, spin-coating might not be suitable for applications that require thick films (>500 nm). To address these issues, a close space sublimation process was implemented to deposit solvent-free and in-situ MAPbBr(3) films with variable thicknesses. A post-deposition annealing protocol was developed that results in smooth perovskite films as thick as 3 mu m. Post-deposition anneal also reduces a photoluminescence emission band that originates from surface defects. The resulting films were chemically, optically and structurally studied and hysteresis-free PIN diodes with metal-oxide semiconductors as p and n-type layers were fabricated and analyzed. The results indicate that high quality perovskite films with variable thickness can be obtained by the close space sublimation (CSS) process demonstrated here. Although MAPbBr(3) was selected for this study, this CSS method demonstrated can be easily applied to other hybrid perovskites.

The oxygen partial pressure during NiO deposition in reactive sputtering of a Ni target is used to control its carrier type and concentration, obtaining both nand p-type films. Carrier concentration can be controlled, ranging from 10(19) to 10(14) cm(-3). Films deposition is performed at 200 degrees C, a relatively low temperature that enables the use of glass as substrate. Experimental band diagrams for n-type NiO are obtained for the first time. Finally, a NiO homojunction is demonstrated by introducing a low carrier concentration layer in between n- and p(+)-type NiO layers. Layers are deposited in situ, preventing contamination and improving the interface quality, as observed by TEM. The Ni:O ratio for each layer was also obtained by analytical TEM measurements, demonstrating the impact of the oxygen partial pressure on the films' stoichiometry and the simplicity of our process to control carrier type and carrier concentration in oxide semiconductors.

We analyze the Al doping effect in CdS films by chemical bath deposition and how it impacts this doping effect in a heterojunction, for the case of ITO/CdS:Al/NiOx/Ni/Au. The results show that the doping effect of aluminum on the CdS films by chemical bath deposition does slightly affect the structural and morphological properties. The impact of the doping is related to the electrical properties; first, with a decrement in the resistivity from 108 to 107 Ω cm, the work function decreases from 4.7 to 4.3 eV, the bandgap and the valence band suffers a small increment of 0.1 eV. The change in the electrical properties impacts the diode behavior, and the increment in the work function leads to an increment of the Fermi energy level difference between NiOx and CdS:Al; this difference was reflected in a wider depletion region and a reduction of the leakage current.