Search results

This paper aims present a thermal touch screen for the blind – a thermal tablet. A blind person using the device can imagine simple graphics or characters by touching flat thermal screen, which consists of reversible heat points, either warm or cold in different time. For the purpose, a thermal touch screen has been designed, fabricated and tested with a help of the blind.

The screen contains 294 Peltier modules working as reversible small heat sources that keep pre-set different temperature. The tablet can easily present thermal images and characters generated directly by an interfaced PC. Design methodology is based on own authors’ patent.

This paper presents original design and construction stages, as well as tests and usefulness of the device. The tests were carried out with participation of blind students who suggested how to tune the final parameters of the device in such a way that presentation and recognition of thermal information is easy and quick.

The thermal tablet consists of original hardware and software. Both of them collaborate each other and make the tablet useful for the blind. It has been proved by series of tests.

The paper aims to present the prototype of a graphical touch screen of thermal signs for the blind.

The surface of every Peltier pump is a touch point that demands the thermal stabilization. Miniature Peltier modules can work both as heat and cold generators. They are also able to measure the required dot temperature. Graphical screen of thermal signs displays a simple symbol or Brail text. Special computer program was made to control this innovative device. The software enables monitoring the temperature of each Peltier module.

The experiments carried out with blind people show that they are able to recognize hot and cold dots. Infrared photos of the device have been made using the thermographic MK525 camera.

The paper illustrates that it is possible to display simple graphics by using Peltier micropumps.

The purpose of this paper is to develop a method of preparing spray-on dopant solutions that enable obtaining a p+ region forming a back-surface field (BSF) during the diffusion doping process. The spray-on method used allows to decrease the costs of dopant solution application, which is particularly significant for new low-cost production processes.

This paper presents steps of production of high concentration boron dopant solutions enabling diffusion doping of crystalline p-type silicon surfaces. To check the fabricated dopant solutions for stability and suitability for spray-on application, their viscosity and density were measured in week-long intervals. The dopant solutions described in this paper were used in a series of diffusion doping processes to confirm their suitability for BSF production.

A method of preparing dopant solutions with parameters enabling depositing them on silicon wafers by the spray-on method has been established. Due to hygroscopic properties of the researched dopant solutions, a maximum surrounding atmosphere humidity has been established. The solutions should not be applied by the spray-on method, if this humidity value is exceeded. The conducted derivatographic examination enabled establishing optimal drying conditions.

The paper presents a new composition of a dopant solution which contains high concentration of boron and may be applied by the spray-on method. Derivatographic examination results, as well as equations describing the relation between dopant solution density and viscosity and storage time are also original for this research. The established dependencies between the sheet resistance of the fabricated BSF and the diffusion doping time are other new elements described in the paper.

The purpose of this study is comparison of the diffusion processes performed using the commercial available dopant paste made by Filmtronics and the original prepared liquid dopant solution. To decrease prices of industrially produced silicon-based solar cells, the new low-cost production processes are necessary. The main components of most popular silicon solar cells are with diffused emitter layer, passivation, anti-reflective layers and metal electrodes. This type of cells is prepared usually using phosphorus oxychloride diffusion source and metal pastes for screen printing. The diffusion process in diffusion furnace with quartz tube is slow, complicated and requires expensive equipment. The alternative for this technology is very fast in-line processing using the belt furnaces as an equipment. This approach requires different dopant sources.

In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution. The investigation was focused on dopant sources fabrication and diffusion processes. The doping solution was made in two stages. In the first stage, a base solution (without dopants) was made: dropwise deionized (DI) water and ethyl alcohol were added to a solution consisting of tetraethoxysilane (TEOS) and 99.8 per cent ethyl alcohol. Next, to the base solution, orthophosphoric acid dissolved in ethyl alcohol was added.

Diffused emitter layers with sheet resistance around 60 Ω/sq were produced on solar grade monocrystalline silicon wafers using two types of dopant sources.

In this work, the diffusion processes were made for two different types of dopant sources. The first one was the commercial available dopant paste from Filmtronics and the second one was the original prepared liquid dopant solution.