Kazimierz Drabczyk

Influence of screen printing parameters on the front metallic electrodes geometry of solar cells

Purpose – The paper aims to present results of investigations carried out on the front electrode of the solar cell. The front-side electrode for solar cells based on crystalline material is obtained by the screen printing method. Screen printing has been the prevailing method of electrode deposition because of its low cost. One of the ways to improve the cell efficiency and reduce the production costs is a further refinement of the metal electrode screen printing process. Design/methodology/approach – The researches were focused on the modification of mechanical parameters of screen printing process to ensure the best possible cross-section of the front electrode geometry. The main printing process parameters were constant, however, the print speed was variable. The obtained fine line of front contact was characterized morphologically – the dimension and geometry of the front contact cross-section – by scanning electron microscopy technique. Findings – The thin paths of 100 μm in width were screen printed...

Electrodeposition of thin metallic layer for solar cell electrodes

Purpose – The paper aims to show application of the electrochemically deposited coatings for thickening of the screen printed electric paths potentially applied in photovoltaic cells. Design/methodology/approach – The electric paths were screen printed with the use of silver-based paste. The paths were thickened by electrodeposition of thin copper layer in potentiostatic regime from surfactant-free plating bath. The morphology and surface quality of the paths were studied by imaging with scanning electron microscopy. Findings – The electric paths can be thickened successfully, but quality for the screen printed substrate determines quality of deposited layer. The EDX analysis confirmed that the deposited copper layer covered uniformly the printed paths. Research limitations/implications – The adhesion of the copper-covered path to the silicon wafer surface depends on adhesion of the original screen printed path. Originality/value – This paper confirms that electrodeposited copper can be applied for screen...

Copper deposition on screen printed electrical paths for solar cell application

Purpose – The aim of this paper is to present results of investigations carried out on the front electrode of solar cells. Nowadays, most worldwide solar cell production is dominated by monocrystalline and polycrystalline silicon as a base material. In such cells, the electrical carriers are collected by the system of metallic paths fabricated on a silicon surface. One possible way to increase cell efficiency and reduce the production costs of solar modules is to replace the expensive silver by cheaper copper in front metallic electrodes. Design/methodology/approach – The paper presents results of investigations performed on the front electrode of the solar cell. The investigations were focused on the modification of typical screen printing fabrication of the thin electrical finger paths of the front solar cell electrode. The resulting contacts were characterized morphologically (the dimensions and geometry of the front contacts) by scanning electron microscopy. The composition of finger path covered with...

Comparison of diffused layer prepared using liquid dopant solutions and pastes for solar cell with screen printed electrodes

Purpose 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. Design/methodology/approach 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. Findings Diffused emitter layers with sheet resistance around 60 Ω/sq were produced on solar grade monocrystalline silicon wafers using two types of dopant sources. Originality/value 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.

Investigation of electrical performance of silicon solar cells with transparent counter electrode

Purpose – The purpose of this paper was the investigation of transparent conducting oxide (TCO) applied as an additional part of front metal electrode of crystalline silicon solar cell. Transparent conducting oxides are widely used as counter electrodes in a wide range of electronics and optoelectronics applications, e.g. flat panel displays. The most important optical and electrical requirements for TCOs are high optical transmittance and low resistivity. This low resistivity might invoke the possibility of increasing the distance between the fingers in the solar cell front electrode, thus decreasing the total area covered by metal and decreasing the shadowing loss. Design/methodology/approach – In the present work, thin films of indium-tin-oxide (ITO) as a transparent counter electrodes, were evaporated on the surface of silicon n+-p junction structures used in solar cells. The influence of the properties of ITO electrode on the electrical performance of prepared solar cells was investigated through opt...

Investigations of electrical and optical properties of functional TCO thin films

Abstract Transparent conducting oxide (TCO) films of indium-tin-oxide were evaporated on the surface of silicon wafers after phosphorous diffusion and on the reference glass substrates. The influence of deposition process parameters (electron beam current, oxygen flow and the substrate temperature) on optical and electrical properties of evaporated thin films were investigated by means of resistivity measurements and optical spectrophotometry. The performance of prepared thin films was judged by calculated figure of merit and the best result was obtained for the sample deposited on the substrate heated to the 100 °C and then removed from the deposition chamber and annealed in an air for 5 minutes at 400 °C. Refractive index and extinction coefficient were evaluated based on measured transmission spectra and used for designing of antireflection coating for solar cell. The obtained results showed that prepared TCO thin films are promising as a part of counter electrode in crystalline silicon solar cell construction.

Spray-on glass solution for fabrication silicon solar cell emitter layer

Purpose The main aim of this study was a preparation development of dopant solution (DS) which can be deposited by a spray-on method and subsequently allows obtaining the n+ emitter layer with surface resistance in the range of 65-80 Ω−1. The intention of chosen spray-on method was to gain a cheaper way of dopant source deposition, compared to the commonly used methods, which is of particular importance for the new low-cost production processes. Design/methodology/approach This paper presents the sequence in producing a spray-on glass solution (DS) with very high concentration of phosphorus, which allows to perform diffusion doping at relatively low temperatures. DS contained deionized water, ethyl alcohol, tetraethoxysilane and othophosphoric acid. Findings The sequence in producing a DS was performed with respect to enabling the application to silicon wafers by spray-on method. Furthermore, the equations defined density and viscosity of DS in term of storage time were referred to determine the possibility of applying this solution by spray-on method. Besides, the dependence of the emitter surface resistance on the doping (diffusion) time was determined. Accordingly, optimal process conditions were specified. Originality/value The paper presents a new, so far unpublished composition of DS with very high concentration of phosphorus, which can be applied using a spray-on method. Moreover, original are also investigations respecting some properties of obtained DS relative to storage time.

Influence of ITO layer application on electrical parameters of silicon solar cells with screen printed front electrode

Purpose The purpose of this paper was investigation and comparison of electrical and optical properties of crystalline silicon solar cells with ITO or TiO2 coating. The ITO, similar to TiO2, is very well transparent in the visible part of optical radiation; however, its low resistivity (lower that 10-3 Ohm/cm) makes it possible to use simultaneously as a transparent electrode for collection of photo-generated electrical charge carriers. This might also invoke increasing the distance between screen-printed metal fingers at the front of the solar cell that would increase of the cell’s active area. Performed optical investigation showed that applied ITO thin film fulfill standard requirements according to antireflection properties when it was deposited on the surface of silicon solar cell. Design/methodology/approach Two sets of samples were prepared for comparison. In the first one, the ITO thin film was deposited directly on the crystalline silicon substrate with highly doped emitter region. In the second case, the TCO film was deposited on the same type of silicon substrate but with additional ultrathin SiO2 passivation. The fingers lines of 80 μm width were then screen-printed on the ITO layer with two different spaces between fingers for each set. The influence of application of the ITO electrode and the type of metal electrodes patterns on the electrical performance of the prepared solar cells was investigated through optical and electrical measurements. Findings The electrical parameters such as short-circuit current (Jsc), open circuit voltage (Voc), fill factor (FF) and conversion efficiency were determined on a basis of I-V characteristics. Short-circuit current density (Jsc) was equal to 32 mA/cm2 for a solar cell with a typical antireflection layer and 31.5 mA/cm2 for the cell with ITO layer, respectively. Additionally, electroluminescence of prepared cells was measured and analysed. Originality/value The influence of the properties of ITO electrode on the electrical performance of crystalline silicon solar cells was investigated through complex optical, electrical and electroluminescence measurements.

Fine line screen printed silver electrodes for copper electrodeposition

Purpose In this paper, results of the studies on the copper deposition on screen-printed fine-line front electrode of the solar cell were presented. The silver consumption is an important problem according to growing silver prices. The proposed solution of those problems might be printing of a very thin silver seed layer and subsequent copper plating. This process can be an alternative for typically used screen printing. The purpose of this study was the optimization of the finger path fabrication process to obtain required geometric of fingers for copper deposition. Design/methodology/approach In this paper, double-step metallization process was analyzed. The first step of an electrode formation is screen printing, the second one is copper electrodeposition. Presented investigations were focused on the optimization of the finger path fabrication process to obtain required geometric dimensions and sharp border of fingers. The morphology of the electrodes was characterized by scanning electron microscope before and after copper deposition. The X-ray analysis of elemental arrangement and cross-section profiles of fingers were made using energy-dispersive X-ray fluorescence spectrometer. Findings Presented investigations were focused on the optimization of the finger path fabrication process to obtain required geometric dimensions and sharp border of fingers without any silver particles. The main problem of non-uniform silver paste distribution close to the border of printed finger paths was eliminated by selection of appropriate paste and printing parameters. The obtained coatings were soft, ductile and bright. Originality/value The novelty of the presented approach is modification of the printing parameters, especially for copper deposition. In this paper, the reasons of the widening of electrodes during the copper deposition process is analyzed.

Silver nanoparticles in the thermal silver plating of aluminium busbar joints

Abstract Thermal silver plating method by means of nanosilver-based paint could be an alternative to electrochemical processes. Electrochemical silver layering on aluminium is typically achieved with an intermediate layer, which provides very good adhesion of the layer to the aluminium surface but increases the resistance of the whole junction system. In the method of silver plating promoted by the authors, the intermediate layer is eliminated. The layer of silver paint was applied directly on the aluminium surface by spraying using aerograph. Procured silver layers, according to ISO 2409, prove proper adhesion to aluminium. The value of contact resistance with a pressure of 300 N cm−2 and current load of 200 A is 0.03 μΩ mm−2, which is comparable to the contact resistance of layers generated by electrochemical means. This new method decreases the level of toxic waste emission and therefore is less harmful for the natural environment. It is also cheaper and simpler than the electrochemical process. An additional advantage is the possibility of silver plating of the chosen surfaces with various shapes.