Cheow Siu Leong

Kajian inframerah ke atas sel-sel suria silikon

Increasing reliance on carbon-based fossil fuel is likely to cause irreversible damage to global environment. Crystalline silicon (Si) based on pollution free photovoltaic (PV) electricity generation technology is expected to play a dominant role in this electricity generation transition from carbon to silicon. Since Si wafer represents almost 50% of the PV conversion cost, thinner wafers are highly effective at reducing the production cost. Therefore, there is an urgent need to develop alternative device configurations and processing methods for thinner Si wafer. Si wafer has to go through cleaning process, thinning process, textured process and partially transparent technique. In this work optical transmission through Si is investigated as a function of wafer thickness. For this improved performance, surface morphology, optical properties and the optical transmission near band gap is measured with custom-designed rear infra-red (IR) transmission measurement system. Si wafer with the textured surface have more light absorption than the as-cut and planar Si wafer.

Analisis prestasi bagi sel suria silikon teringkas ke atas silikon wafer kristal jenis-P

Crystalline silicon (c-Si) wafers are the dominating substrate materials for solar cells in current photovoltaic (PV) industry. Silicon (Si) wafer with positive-type (p-type) based solar cells dominates almost 95% of the global PV market. Recent goal in Si solar cell industry is focusing on cost reduction through inexpensive manufacturing processes. Standard manufacturing process of Si solar cell fabrication consist of damage removal, cleaning, texturing, phosphorus oxytrichloride (POCl3) diffusion, antireflective coating (ARC) deposition, metallization by screen printing technique, firing and light current-voltage (LIV) testing. These fabrications line are time–consuming and high temperature process which lead to high manufacturing cost. This study presents the simplification of Si solar cell fabrication on p-type Si wafer. Simplified fabrication process eliminates the ARC deposition by plasma enhanced chemical vapour deposition (PECVD). Simplified Si solar cell was fabricated without silicon nitride (SiN) as ARC layer. In commercial solar cell, both pyramid texture on Si wafer and SiN have been used to reduce reflectance and enhanced the light absorption. From the reflectance measurement, it can be seen that SiN and pyramid texture shows an average reflectance curve. The efficiency obtained by commercial, fabricated and simulated solar cells were 17.09%, 9.44% and 9.67%, respectively. From the simulation study, it is proven that the low efficiency of simplified solar cell was attributed by low minority carrier lifetime of p-type Si wafer.

Investigation near IR absorption in thin crystalline Si wafers with randomly etched nano-pillars

Significant research has been focused on optimizing efficiency of crystalline silicon solar cells with nanostructured surfaces. Light absorption is greatly enhanced by light trapping in nanostructures. The main focus of research work presented here is to enhance the broadband light absorption in randomly etched nano-pillar textures. The nano-pillars were formed through metal-assisted chemical etching (MACE) process with silver nanoparticles serving as the etch masks. Uniformly distributed nano-pillars (SiNPs) were fabricated using single step etch process. Nano-pillars were fabricated on thin (∼ 150 µm) c-Si substrates by immersion into an aqueous solution of HF, AgNO3, and H2O2. The nano-pillars morphology and optical response were characterized with Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), and near IR transmission. The performance of growth nano-pillars on as-cut (without saw damage removal process) and planar substrate (with saw damage removed) was evaluated. Typical dimension...

Pulsed solar panel light current-voltage characterization based on Zener diode

Application of Zener diode for light current-voltage (LIV) characterization of a solar panel is reported. A typical solar panel is simply a configuration of large number of solar cells connected in series. In order to characterize solar panel light current-voltage (LIV) response, a pulsed light source uniformly illuminates the solar panel, and its current-voltage response is measured using either one of three approaches: variation of resistance, current, or voltage across its output. In this paper, the solar panel LIV data acquisition system is based on variation of computer-controlled direct current (DC) power supply in conjunction with a Zener diode. At the start of the measurement, power supply voltage is set to zero and is slowly increased to balance the solar panel voltage. As power supply voltage becomes larger than solar panel voltage, it becomes reverse-biased under light illumination. The solar panel voltage is reduced to zero and its short-circuit current (Isc) value is measured. For the open-circuit voltage (Voc) measurement, no current must flow through the circuit. Ideally, this condition requires an infinite resistor in the measurement circuit. In order to approximate the infinite resistor for Voc measurement, a Zener diode was investigated. A Zener diode has the ideal characteristic that under reverse bias conditions, it allows no current flow until its breakdown voltage is reached. The breakdown voltage of Zener diodes is configurable over a broad range. Solar panel LIV measurements were successfully demonstrated over a voltage range of up to 22 V.

Oxide passivated low reflection nano-structured solar cell

The main processes in conventional silicon solar cell manufacturing are surface cleaning, saw damage removal, and texturing. These steps require excessive water and chemical usage. In addition 10% of the wafers are wasted through etching. These steps are followed by surface passivation and reflection reduction through expensive and inflammable, toxic-gas based plasma enhanced chemical vapor deposition process for deposition of high index anti-reflection SiN films. Surface reflection measurements from these surfaces have been carried out was comparable or 1% lower than SiN-coated surfaces and eliminating the need for deposition of high index SiN films. Si nanostructure passivation has been achieved with an oxide film grown as part of the POCl3 emitter process. These innovations have significantly reduced water and chemical usage, and have also eliminated expensive, silane-based plasma processing without restructuring the existing industrial manufacturing process.