RESUMEN
Thin-film thermocouple (TFTC) technology is a novel measurement method that produces a thermocouple sensor during the deposition process, even though it is a complex surface, to obtain the surface temperature. TFTC is a thin film sensor for measuring temperature by contact methods, consisting of two different metals which can generate thermoelectric forces named "Seebeck effects". In the past decade there have been many attempts to measure the cutting temperature during machining processes using TFTF sensors. However, research has not yet progressed to optimize the sensor performance or fabrication process. This paper studies a preliminary technique for the fabrication of a TFTC sensor on a cutting tool surface and optimizes the deposition conditions, TFTC design, and sensor performance. Chromel and Alumel, which are materials commonly used in K-type thermocouples, were used for the thermal evaporation process. When the Chromel has a nickel to chrome ratio of 9:1, low resistivity and minimal variation with increasing temperature were observed. When the contact area of the deposited electrode (+) and (-) poles increased, the resistivity decreased and the TFTC sensitivity improved. Data acquisition tests using a DAQ system connected to the TFTC sensor show the lowest resistivity in TFTC B and C types are able to measure temperature data. It is expected that the heat generated during the cutting process can be detected using the TFTC sensor with B-type shape and Chromel with a 9:1 nickel to chrome ratio.
RESUMEN
The energy level offset at inorganic layer-organic layer interfaces and the mismatch of hole/electron mobilities of the individual layers greatly limit the establishment of balanced charge carrier injection inside the emissive layer of halide perovskite light-emitting diodes (PeQLEDs). In contrast with other types of light-emitting devices, namely OLEDs and QLEDs, various techniques such as inserting an electron suppression layer between the emissive and electron transport layer have been employed as a means of establishing charge carrier injection into their respective emissive layers. Hence, in this study, we report the use of a thin layer of Poly(4-vinylpyridine) (PVPy) (an electron suppression material) placed between the emissive and electron transport layer of a halide PeQLEDs fabricated with an inverted configuration. With ZnO as the electron transport material, devices fabricated with a thin PVPy interlayer between the ZnO ETL and CsPbBr3 -based green QDs emissive layer yielded a 4.5-fold increase in the maximum observed luminance and about a 10-fold increase in external quantum efficiency (EQE) when compared to ones fabricated without PVPy. Furthermore, the concentration and coating process conditions of CsPbBr3 QDs were altered to produce various thicknesses and film properties which resulted in improved EQE values for devices fabricated with QDs thin films of lower surface root-mean-square (RMS) values. These results show that inhibiting the excessive injection of electrons and adjusting QDs layer thickness in perovskite-inverted QLEDs is an effective way to improve device luminescence and efficiency, thereby improving the carrier injection balance.
RESUMEN
A desire to achieve optimal electron transport from the electron transport layer (ETL) towards the emissive layer (EML) is an important research factor for the realization of high performance quantum dot light-emitting diodes (QD-LEDs). In this paper, we study the effect of a single, double, and electron transport layer sandwiched Poly(4-vinylpyridine) (PVPy here on) on the charge injection balance and on the overall device performance of InP-based red quantum dot light emitting diodes (red QD-LEDs). The results showed general improvement of device characteristic performance metrics such as operational life with incorporation of a PVPy interlayer. The best performance was observed at a lower concentration of PVPy (@ 0.1 mg/mL) in interlayer with continual worsening in performance as PVPy concentration in the interlayer increased in other fabricated devices. The AFM images obtained for the different materials reported improved surface morphology and overall improved surface properties, but decreased overall device performance as PVPy concentration in interlayer was increased. Furthermore, we fabricated two special devices: in the first special device, a single 0.1 mg/mL PVPy sandwiched between two ZnO ETL layers, and in the second special device, two 0.1 mg/mL PVPy interlayers were inter-sandwiched between two ZnO ETL layers. Particular emphasis was placed on monitoring the maximum obtained EQE and the maximum obtained luminance of all the devices. The first special device showed better all-round improved performance than the second special device compared to the reference device (without PVPy) and the device with a single 0.1 mg/mL PVPy interlayer stacked between ZnO ETL and the emissive layer.
RESUMEN
We investigated the performance of single-structured light-emitting electrochemical cell (LEC) devices with Ru(bpy)3(PF6)2 polymer composite as an emission layer by controlling thickness and heat treatment. When the thickness was smaller than 120-150 nm, the device performance decreased because of the low optical properties and non-dense surface properties. On the other hand, when the thickness was over than 150 nm, the device had too high surface roughness, resulting in high-efficiency roll-off and poor device stability. With 150 nm thickness, the absorbance increased, and the surface roughness was low and dense, resulting in increased device characteristics and better stability. The heat treatment effect further improved the surface properties, thus improving the device characteristics. In particular, the external quantum efficiency (EQE) reduction rate was shallow at 100 °C, which indicates that the LEC device has stable operating characteristics. The LEC device exhibited a maximum luminance of 3532 cd/m2 and an EQE of 1.14% under 150 nm thickness and 100 °C heat treatment.