Heriyanto Syafutra

Manufactures and Characterizations of Photodiode Thin Film Barium Strontium Titanate (BST) Doped by Niobium and Iron as Light Sensor

Pure Ba0,5Sr0,5TiO3 (BST) thin film, BST doped by niobium (BNST) and BST doped by iron (BFST) have been synthesized on p‐type Si (100) substrates using Chemical Solution Deposition (CSD) methods followed by spin coating and annealing techniques. Current‐voltage characterizations on these sample result in agreement that all of the BST, BNST, and BFST thin films have photodiode properties. Electrical conductivity values of BST, BNST, and BFST are in the range of conductivity values of semiconductor materials. Niobium or iron doping on the BST samples increase their conductivity value their dielectric constant. This conductivity values may change when a light is exposed on the film surface. Absorbance and reflectance characterizations show that the BST, BNST, and BFST thin films absorb certain range of visible and infrared light. It is convincing that the BST, BNST, and BFST thin films might be used as photodiode light sensor.

Development of Luxmeter Based on Ba0,25Sr0,75TiO3 Ferroelectric Material

Ba0,25Sr0,75TiO3 (BST) thin films has been deposited on a Si (100) p‐type substrate by chemical solution deposition (CSD) method followed by spin coating technique (at 3000 rpm rotational speed for 30 seconds) and annealing process at the temperature around 850° C for 15 hours. The films show a maximum optical absorption at green light. An I–V investigation on the films results in agreement that the thin films have a photodiode characteristic. Electrical conductivity of the BST thin films is in the range of 2.79×10−7 to 5.3×10−7 S/cm, it is the range of semiconductor materials. The electrical conductivity and photocurrent increase when the light intensity increases from 1000 to 6000 Lux. A BST thin film has been utilized as a light meter in an ATMega8535 microcontroller since it is sensitive with a light intensity change. Base on calibration and validation curves, a measurement using this microcontroller results in comparable light intensity values with that result from a standard instrument.

Modified Spin Coating Method for Coating and Fabricating Ferroelectric Thin Films as Sensors and Solar Cells

Spin coating process with a modified spin coater is performed well, especially the second generation of modified spin coater, which has a maximum value of 18,000 rpm, is able for manufacturing/coating photonic crystal‐based ferroelectric thin films that require a high angular velocity (rpm). Ferroelectric thin films that use both 3000 and 6000 rpm have given good results in energy gap, electrical conductivity, etc. In addition, the modified spin coater has also produced several applications such as sensors in the device of blood sugar level noninvasively, sensors in the automatic drying system, sensors in the robotic system, and photovoltaic cells in the system of solar cells/panels which are being developed at present. These applications used ferroelectric material such as barium strontium titanate (BST), lithium niobate (LiNbO3), cuprous oxide (CuO), and lithium tantalate (LiTaO3).

The effect of spectrum range limitation to the efficiency of Al0.3Ga0.7As/GaAs/InP/Ge multijunction solar cells: a simulation case

The effect of Spectrum Range Limitation (SRL) to the efficiency and performances of multijunction solar cells Al0.3Ga0.7As/GaAs/InP/Ge was investigated using simulation approach. Simulations were done using two different models, first with No Spectrum Range Limitation (NSRL) and the second with SRL. In the first model each subcell (material) was free to absorb AM1.5G solar radiation spectrum from 280 nm up to 2500 nm, while for the second model, the absorption spectrum for each subcell depends on the cut-off wavelength of its previous subcell. For each model, a non-identical current flow in each layer was simulated. The results have shown that SRL dropped the efficiency by almost a half (44.90 %) compared to simulation with NSRL. All current-producing simulations were performed using freely available PC1D program.

Ideal simulation of Al0.3Ga0.7As/InP/Ge multijunction solar cells

Increasing the efficiency of solar cell is one of the most challenging tasks for material scientists nowadays. Computer simulation on the other hand, could be used to maximize this effort. In this paper we present our investigations on Al0.3Ga0.7As/InP/Ge multijunction solar cells. These multijunction solar cells were designed and simulated using PC1D program in two different models. Model 1 focuses on maximizing the efficiency of each subcell, while in model 2 we forced identical current flowing in each subcell. Simulations for both models were performed under ideal conditions of blackbody spectrum at T=6000 K (at the top of atmosphere) and solar intensity of 0.1367 W/cm2. Our results show that model 1 produces efficiency up to 38.86% compared to 20.26% that produced by model 2.