Mechanical Stability in Crystalline Silicon Solar Cells

Mechanical stability of back contact solar cells deteriorates when holes (MWT, EWT) or grooves (TWT) are created in the wafer. These operations are essential for these structures so we found necessary to quantify the magnitude of this damage. A set of wafers with the EWT structure was produced and its mechanical strength measured by the Ring on Ring bending test. Other two sets of wafers with similar processes were prepared and tested to compare the effect of different fabrication steps on mechanical strength of the wafer. A numeric model was developed to analyse the data from the Ring on Ring test and a statistical study was carried out

Detección y análisis de grietas en sustratos de silicio cristalino originadas en líneas industriales de fabricación de células solares

164 p.Siendo la oblea de silicio cristalino uno de los elementos más costosos de los paneles fotovoltaicos, el objetivo de esta tesis es comprender el proceso de fractura de las obleas de silicio cristalino en las líneas de fabricación de células solares fotovoltaicas y establecer las acciones necesarias para reducir el índice de roturas en estas líneas.Para ello, se ha estudiado el proceso de la fractura frágil, y se ha analizado una línea de fabricación de células solares estándar. De esta forma se han detectado, no sólo los puntos críticos donde se produce un mayor número de roturas, sino también aquellos donde se generan las grietas que posteriormente conducirán a la fractura de la oblea.Se han analizado diferentes técnicas para detectar grietas en las obleas y poder retirarlas del proceso productivo antes de que se produzca su rotura y genere costes adicionales. Por último se ha estudiado el deterioro mecánico que produce la generación de una estructura de célula de contactos posteriores en una oblea de silicio y diversas técnicas para la reducción del deterioro generad

Study of the Mechanical Strength Improvement of Wafers for EWT Solar Cells by Chemical Etching after the Drilling Process

Mechanical stability of EWT solar cells deteriorates when holes are created in the wafer. Nevertheless, the chemical etching after the hole generation process improves the mechanical strength by removing part of the damage produced in the drilling process. Several sets of wafers with alkaline baths of different duration have been prepared. The mechanical strength has been measured by the ring on ring bending test and the failure stresses have been obtained through a FE simulation of the test. This paper shows the comparison of these groups of wafers in order to obtain an optimum value of the decreased thickness produced by the chemical etchin

Study of the Mechanical Strength Improvement of Wafers for EWT Solar Cells by Chemical Etching after the Drilling Process

Mechanical stability of EWT solar cells deteriorates when holes are created in the wafer. Nevertheless, the chemical etching after the hole generation process improves the mechanical strength by removing part of the damage produced in the drilling process. Several sets of wafers with alkaline baths of different duration have been prepared. The mechanical strength has been measured by the ring on ring bending test and the failure stresses have been obtained through a FE simulation of the test. This paper shows the comparison of these groups of wafers in order to obtain an optimum value of the decreased thickness produced by the chemical etchin

Study of the effect of different hole sizes on mechanical strength of wafers for back contact solar cells

Drilling process on wafers to produce EWT or MWT solar cells is a critical fabrication step, which affects on their mechanical stability. The amount of damage introduced during drilling process depends on the density of holes, their size and the chemical process applied afterwards. To quantify the relation between size of the holes and reduction of mechanical strength, several sets of wafers have been prepared, with different hole diameter. The mechanical strength of these sets has been measured by the ring on ring bending test, and the stress state in the moment of failure has been deduced by FE simulation

Damage reduction of the laser drilling process on back contact solar cells by chemical treatment

Production of back contact solar cells requires holes generations on the wafers to keep both positive and negative contacts on the back side of the cell. This drilling process weakens the wafer mechanically due to the presence of the holes and the damage introduced during the process as microcracks. In this study, several chemical processes have been applied to drilled wafers in order to eliminate or reduce the damage generated during this fabrication step. The treatments analyzed are the followings: alkaline etching during 1, 3 and 5 minutes, acid etching for 2 and 4 minutes and texturisation. To determine mechanical strength of the samples a common mechanical study has been carried out testing the samples by the Ring on Ring bending test and obtaining the stress state in the moment of failure by FE simulation. Finally the results obtained for each treatment were fitted to a three parameter Weibull distributio

Crack origin and detection in thin cristallyne solar cells in a production line

In order to reduce cost and make up for the rising price of silicon, silicon wafers are sliced thinner and wider,eading to weaker wafers and increased breakage rates during fabrication process. In this work we have analysed different cracks origins and their effect on wafer’s mechanical strength. To enhance wafer’s strength some etching methods have been tested. Also, we have analysed wafers from different points of an entire standard production process. Mechanical strength of the wafers has been obtained via the four line bending test and detection of cracks has been tested with Resonance Ultrasonic Vibration (RUV) system, developed by the University of South Florida

Detección y análisis de grietas en sustratos de silicio cristalino originadas en líneas industriales de fabricación de células solares

164 p.Siendo la oblea de silicio cristalino uno de los elementos más costosos de los paneles fotovoltaicos, el objetivo de esta tesis es comprender el proceso de fractura de las obleas de silicio cristalino en las líneas de fabricación de células solares fotovoltaicas y establecer las acciones necesarias para reducir el índice de roturas en estas líneas.Para ello, se ha estudiado el proceso de la fractura frágil, y se ha analizado una línea de fabricación de células solares estándar. De esta forma se han detectado, no sólo los puntos críticos donde se produce un mayor número de roturas, sino también aquellos donde se generan las grietas que posteriormente conducirán a la fractura de la oblea.Se han analizado diferentes técnicas para detectar grietas en las obleas y poder retirarlas del proceso productivo antes de que se produzca su rotura y genere costes adicionales. Por último se ha estudiado el deterioro mecánico que produce la generación de una estructura de célula de contactos posteriores en una oblea de silicio y diversas técnicas para la reducción del deterioro generad