Author: GUILLERMO RUIZ TABOADA

Análisis de las características de celdas solares basadas en heteroestructuras ITO/n-Si.

GUILLERMO RUIZ TABOADA (2008)

This work is focused on a theoretical study of an experimental solar cell, fabricated on a tin-doped indium oxide-silicon (ITO-Si) heterostructure. A 10 omega-cm resistivity silicon substrate was used. The main characteristics of the p-n and Schottky barrier physical models were analyzed. The application limits of each model were clearly defined. Based on the previous analysis, It was found that the experimental structure can be considered as a surface inversion p+-n junction and a theoretical model for inversion p-n ITO-nSi solar cells has been developed. This model is able to describe the behavior of such structure in an accurate way. Based on a p+-n model, theoretical calculations are presented. They show an

excellent agreement with the experimental results. Such agreement gave us the possibility to calculate the photovoltaic characteristics of hypothetical ITOnSi solar cells. It was found that the use of silicon substrates with resistivities lower than 10 omega-cm improves the cell efficiency. Moreover, it is shown that using substrates with resistivities lower than 1 omega–cm, the p-n model is not applicable. With the purpose of obtaining similar p-n structures as those obtained with ITO-Si, and based on the knowledge of the shallow and low resistive junctions formed by rapid thermal processes (RTP); p-n solar cells were fabricated by using this technique and a solid dopant source (spin on dopant SOD). The best characteristics achieved by these cells were below the theoretical values predicted by p-n model. A fabrication process depuration is proposed as a future work

En este trabajo se realiza el estudio teorico de una celda solar experimental basada en la heteroestructura ITO-Si fabricada en un substrato de silicio cristalino con resistividad de 10 omega–cm. Se realiza un analisis teorico de las principales caracteristicas de los modelos fisicos p-n y de barrera Schottky, definiendo claramente los limites de aplicacion de cada uno. Con base en esto, se encuentra que la celda experimental puede ser considerada como una union p+-n por inversion superficial del substrato y se desarrolla un modelo fisico y matematico capaz de describir de manera precisa el comportamiento de esta estructura experimental. Se presentan calculos teoricos con resultados que muestran una concordancia excelente con los valores experimentales, lo cual permite visualizar una mejora en las figuras de merito de la estructura mediante el empleo de substratos con resistividad menor a los 10 omega–cm. Se encuentra que para el caso de substratos con resistividad menor a 1 omega–cm, el modelo p-n por inversion superficial del substrato ya no sera aplicable. En un esfuerzo por obtener estructuras p-n similares a las logradas con las celdas ITO-Si, se fabricaron celdas solares en substratos de silicio cristalino basadas en estructuras p-n mediante el uso de una fuente solida SOD (spin on dopant por su siglas en ingles) y un proceso termico rapido de difusión (RTP rapid thermal process por sus siglas en ingles), en base al conocimiento previo de la formacion de uniones poco profundas (menores a 0.46m) y de baja resistividad mediante el empleo de esta tecnica. Las mejores caracteristicas de las estructuras fabricadas con esta técnica presentaron valores menores a los calculos teoricos proporcionados por el modelo p-n. Como trabajo futuro se propone una mejora a este proceso.

Master thesis

Solar cells P-N junctions Indium compounds CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA DISEÑO DE CIRCUITOS

Efficient ITO–Si solar cells and power modules fabricated with a low temperature technology: Results and perspectives

OLEKSANDR MALIK FRANCISCO JAVIER DE LA HIDALGA WADE CARLOS ZUÑIGA ISLAS GUILLERMO RUIZ TABOADA (2008)

ITO–SiOx–nSi semiconductor–insulator–semiconductor (SIS) structures have been produced with a simple spraying technique. It is shown that the structures obtained in such a way may be considered as an induced p–n diode, in which the polycrystalline tin–doped indium oxide (ITO) layer spray deposited on the preliminary treated silicon surface leads to an inversion p-layer at the interface. Solar cells with an active area of 1–4 cm2 have been fabricated based on ITO–SiOx–nSi structures and studied. Under AM0 illumination conditions, the efficiency is nearly 11%, whereas it exceeds 12% for AM1.5 illumination conditions. The theoretical analysis provided in this work shows a good agreement with experimental results and allows for predicting the efficiency of the cells depending on the silicon electro-physical properties.

Article

Silicon Solar cells Photovoltaics Indium tin oxide and other transparent conductors CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ELECTRÓNICA