In this study, double-layered TCO (transparent conductive oxide) films were produced by depositing two distinct TCO materials: SnO₂ works as an n-type layer and ITO (indium-doped tin oxide) serves as a transparent conductor. Both transparent conductive oxide-films were sequentially deposited by sputtering. The electrical and optical properties of single-layered TCO films (SnO₂) and double-layered TCO (ITO/SnO₂) films were investigated. A TCO-embedding photodetector was realized through the formation of an ITO/SnO₂/p-Si/Al layered structure. The remarkably high rectifying ratio of 400.64 was achieved with the double-layered TCO device, compared to 1.72 with the single-layered TCO device. This result was attributed to the enhanced electrical properties of the double-layered TCO device. With respect to the photoresponses, the photocurrent of the double-layered TCO photodetector was significantly improved: 1,500% of that of the single-layered TCO device. This study suggests that, due to the electrical and optical benefits, double-layered TCO films are effective for enhancing the photoresponses of TCO photodetectors. This provides a useful approach for the design of photoelectric devices, including solar cells and photosensors.

A high-performing photoelectric device was realized for the MoS₂-embedded Si device. MoS₂-coating was performed by an available large-scale sputtering method. The MoS₂-layer coating on the p-Si spontaneously provides the rectifying current flow with a significant rectifying ratio of 617. Moreover, the highly optical transmittance of the MoS₂-layer provides over 80% transmittance for broad wavelengths. The MoS₂-embedded Si photodetector shows the sensitive photo-response for middle and long-wavelength photons due to the functional MoS₂-layer, which resolves the conventional limit of Si for long wavelength detection. The functional design of MoS₂-layer would provide a promising route for enhanced photoelectric devices, including photovoltaic cells and photodetectors.

Currently, power conversion system which converts AC to DC Power is applied in domestic urban railway. The diode rectifier is used in most of them. However the diode rectifier can not control the output voltage and can not regenerate power as well. On the other hand, PWM (pulse width modulation) converter using IGBT (isolated gate bipolar transistor) can control output voltage, allowing it to reduce the output voltage drop. Moreover the Bi-directional conduction regenerates power which does not require additional device for power regeneration control. This paper compared the simulation results for the DC power supply system on both the diode rectifier and the PWM converter. Under the same load condition, simulation circuit for each power supply system was constructed with the PSIM (performance simulation and modeling tool) software. The load condition was set according to the resistance value of the currently operating impedance of light rail line, and the line impedance was set according to the distance of each substations. The train was set using a passive resistor. PI (proportional integral) controller was applied to regulate the output voltage. PSIM simulation was conducted to verify that the PWM Converter was more efficient than the diode rectifier in DC Traction power supply system.

Citations

• Analysis of the Cost of Power Loss and Grounding of the Gumi City Tram Power Grid by Reflecting the Dynamic Resistance Model of Tram and the Temperature Characteristics of Tram
  Jeong-Seok Bae, Yun-Ji Choi, Hee-Jin Lee
  The Journal of Korean Institute of Information Technology.2025; 23(5): 55.     CrossRef