The CH 3 NH 3 PbI 3 films were synthesized by a facile low-cost solution process and were used to fabricate photoconductive detectors. The perovskite photodetector is very sensitive to light, with a high responsivity of 5.51[Formula: see text]mA/W and a sensitivity of 50 at 5[Formula: see text]V under 350[Formula: see text]nm light illumination. The device exhibits the fast rise and decay processes with similar appearance, and the relaxation time constants are 270 and 300[Formula: see text]ms, respectively. The photo-current shows an evident saturation, without further increase for prolonging the illumination period. The perovskite photodetectors display high responsive performances to short-wavelength lights. This study is expected to provide a fundamental knowledge of perovskite photodetectors with high speed and repeatability for practical applications.

Amorphous ZnTiSnO (ZTTO) thin films were prepared by the combustion-solution method at low temperatures.Thin-film transistors (TFTs) were fabricated using the ZTTO film as the channel layer.The effects of introduced Ti on the film properties (e.g.,structural and optical properties and chemical states of elements) and device behavior of the TFTs were investigated in detail.The results show that all films are in an amorphous state and display a high average transmittance over 84％ in the visible light region.A moderate Ti content in the matrix can act as carrier inhibitor to effectively reduce the density of oxygen vacancy defects,and so the TFT behaviors are improved.When the molar ratio of Zn/Ti is 30/1,the ZTTO TFTs exhibit acceptable performances with an on/off current ratio of 3.54 × 105.

Amorphous ZnSnO (a-ZnSnO) thin films were synthesized by a combustion solution method to fabricate thin-phototransistors. The a-ZnSnO phototransistors are extremely sensitive to UV light, with evident photoelectric effect identified at various gate voltages. The UV sensitivity is rather high (similar to 10(5) for the ratio of photocurrent to dark-current) at the off-state, while it is quite low (similar to 10(1)) at the on-state. The device behaviors can completely recover to the original state within 2000 s after switching off the UV light at both on-and off-states. We demonstrate that the UV behaviors of a-ZnSnO phototransistors can be well controlled by gate voltages. This paper is expected to provide a fundamental knowledge of performances of amorphous oxide phototransistors for practical applications.

Zn doped Tin oxide (SnO2:Zn) nanoparticles have been synthesized by the chemical precipitation route with different thermal decomposition temperatures having emission intensities in visible light and narrowed bandgap. Band gap narrowing and emission intensities can be controlled by doping and calcination. The average particle sizes estimated by TEM agree with those calculated by XRD to be around 18.48 and 21.44 nm and the optical bandgap values found to be 1.30 and 2.52 eV in SnO2:Zn annealed at 400 and 600 °C, respectively. Blue shift in bandgap and decrease in photoluminescence intensity is noticed in (SnO2:Zn) nanoparticles with high annealing temperature, which is due to large grain sizes. As the grain sizes grow so defect density decreases and crystallanity increases. These defects act as luminescent centers and cause decrease in emission intensity and increase in band gap.

Amorphous AlSnO (a-ATO) thin films have been synthesized by a combustion solution process at low temperatures, with the Al:Sn molar ratio of 1:x (x = 11 − 7) in the precursors. The influence of compositions on the structural, optical, and electrical properties of AlSnO (ATO) films were investigated in detail. The X-ray diffraction patterns revealed that all the ATO films are amorphous in nature. All elements were distributed uniformly over the films, regardless of holes formed in the matrix with increasing Al contents. The a-ATO films had an average transmittance over 80% in the visible region, with enlarged optical band gap energies from 3.42 to 3.67 eV at elevated Al contents. Hall-effect measurements identified that weak p-type conductivity could be obtained at the high Al doping levels with Al:Sn ratios higher than 1:9. The realization of p-type a-ATO films by the combustion solution method may open a door to design p-type amorphous-oxide-semiconductor thin-film transistors for transparent electronics.

Amorphous zinc-tin oxide (a-ZTO) films are fabricated using a combustion solution process. Utilization of a-ZTO films as the novel active layers, ultraviolet (UV) and ethanol sensors are prepared for the first time. The sensor performances are strongly related to the film resistance, which is determinated by the surface O-2(-) formed by O-2 + e = O-2(-) during UV and ethanol detections. During UV exposure, the resistivity of a-ZTO films decreases from 6.50 x 10(5) Omega cm to 56.85 Omega cm, which are very sensitive towards UV (365 nm) light and the photodetectors own a sensitivity value of 650 from 0 to 30 V. While for ethanol gas, the detection regions can be in a wide range from 20 ppm to 500 ppm. The gas response can achieve a value of 31.18 at 500 ppm ethanol and good response/recovery speed (6s and 3 s), which can be comparable with that of the common used nanomaterials. The novel a-ZTO film based UV and gas sensors are very promising researches for future UV and gas sensor applications. (C) 2015 Elsevier B.V. All rights reserved.

A combustion solution method was developed to fabricate amorphous ZnAlSnO (a-ZATO) for thin-film transistors (TFTs). The properties of a-ZATO films and behaviors of a-ZATO TFTs were studied in detail. An appropriate Al content in the matrix could suppress the formation of oxygen vacancies efficiently and achieve densely amorphous films. The a-ZATO TFTs exhibited acceptable performances, with an on/off current ratio of ∼106, field-effect mobility of 2.33 cm2·V−1·S−1, threshold voltage of 2.39 V, and subthreshold swing of 0.52 V/decade at an optimal Al content (0.5). The relation between on- and off-resistance of the ZATO TFT was also within the range expected for fast switching devices. More importantly, the introduced Al with an appropriate content had the ability to evidently enhance the device long-term stability under working bias stress and storage durations. The obtained indium- and gallium-free a-ZATO TFTs are very promising for the next-generation displays.

Responses of the ZATO TFTs towards 365 nm UV illumination.

Amorphous zinc-indium-tin oxide (a-ZITO) thin-film transistors (TFTs) have been prepared using a low-temperature combustion process, with an emphasis on complete miscibility of In and Sn contents. The a-ZITO TFTs were comparatively studied in detail, especially for the working stability. The a-ZITO TFTs all exhibited acceptable and excellent behaviors from Sn-free TFTs to In-free TFTs. The obtained a-ZTO TFTs presented a field-effect mobility of 1.20 cm2 V−1 s−1, an on/off current ratio of 4.89 × 106, and a long-term stability under positive bias stress, which are comparable with those of the a-ZIO TFTs. The In-free a-ZTO TFTs are very potential for electrical applications with a low cost.

X-ray photoelectron spectroscopy (XPS) was utilized to measure the valence band offset (ΔEV) of the TiZnSnO (TZTO)/Si heterojunction. TZTO films were deposited on Si (100) substrates using magnetron sputtering at room temperature. By using the Zn 2p3/2 and Sn 3d5/2 energy levels as references, the value of ΔEV was calculated to be 2.69 ± 0.1 eV. Combining with the experimental optical energy band gap of 3.98 eV for TZTO extracted from the UV-vis transmittance spectrum, the conduction band offset (ΔEC) was deduced to be 0.17 ± 0.1 eV at the interface. Hence, the energy band alignment of the heterojunction was determined accurately, showing a type-I form. This will be beneficial for the design and application of TZTO/Si hybrid devices.

We investigate the electrical properties of ZnO thin-film transistors (TFTs) under the ultraviolet (UV) light illumination to clarify the device reliability. The ON/OFF current ratio of ZnO TFTs shows an evident reduction due to the creation of UV photo-induced current. This behavior degradation becomes severe for devices exposed to a short-wavelength UV light. The persistent photoconductivity is observed in ZnO TFTs under the UV illumination with a much slower decay for the ON-state than the OFF-state, which is attributed to the reduced recombination under a positive gate bias. The UV light instabilities of ZnO TFTs can be explained on the basis of UV photoexcited oxygen vacancies. A feasible mechanism model is proposed in this paper. These observations and analytical model not only provide useful physical insight into the device behaviors, but also offer basic design guideline for oxide TFTs.

A multi-step chemical wet-etching method, with a process of ZnO:Al (AZO) deposition, NH3 center dot H2O etching, AZO re-deposition and HCl re-etching, is developed to obtain a wide range distribution of texture features for improving the light trapping. The first mild step with a NH3 center dot H2O etching process (for 4 min) results in tiny craters with a lateral feature size of 100-400 nm and root mean square (RMS) roughness of 34.5 nm, which provides an effective light trapping for the short wavelength. The second HCl etching (for 15 s) aims at texturing strong pits with similar to 1.5 mu m feature size and similar to 75 nm RMS, which leads to enhanced light trapping in the long wavelength. The diffuse transmittance increases from 9.0% to 51.6% due to the enhanced light scattering by the double-layered texture with the NH3 center dot H2O and HCl etching processes. The corresponding highest haze value of 59.6% is obtained compared to that of 6.8% at 550 nm due to the re-etching process for the NH3 center dot H2O-etched sample. This multi-step method will lead to a broad surface feature distribution of 100-1500 nm, where the electrical properties remain a slight change. Such good double texture surfaces prepared by the novel etching method promote the potential application of AZO films in thin film solar cells. (C) 2013 Elsevier B. V. All rights reserved.