Antireflective coatings of amorphous carbon and silicon for crystalline silicon solar cells

Author(s)

Douglas Soares da Silva

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Física Gleb Wataghin
• Defense date: 2009-03-27

Examining board members

Francisco das Chagas Marques; Manuel Cid Sanchez; Lucila Helena Deliesposte Cescato

• Advisor: Francisco das Chagas Marques

Abstract

In this thesis we propose the use of amorphous carbon as a possible candidate for use as antireflective layer in crystalline silicon solar cells. The amorphous carbon can be prepared with high band gap and important properties such as high hardness, low coefficient of friction, prepared at room temperature, etc. Moreover, the amorphous carbon material is abundant in nature and its use in electronics could reduce the consumption of toxic materials, helping to reduce damage to the environment. We explored the optical properties of carbon films and carbon silicon produced by different methods of deposition (RF Glow Discharge, RF Sputtering and FCVA_Filtered Cathodic Vacuum Arc) to the application as antireflective coatings in solar cells. The study of optical properties of films, such as forbidden band, index of refraction, absorption coefficient and integrated reflection were crucial to the conclusions of this work. For that, it was important the manufacture of solar cells and the study of key photovoltaic parameters: efficiency, short-circuit current, open circuit voltage and fill factor. The single crystal silicon solar cells were developed from the widely known technique of thermal diffusion of phosphorus doping, the pn homojunctions. Different antireflective structures based on carbon were studied and compared. Thus, we investigated the use of carbon type diamond (diamond-like carbon DLC), carbon type polymer (polimeric-like carbon - PLC), tetrahedral carbon (ta-C), silicon carbide (a-CxSix-1: H). For purposes of comparison with conventional antireflective layers, we adopted the tin dioxide (SnO2) deposited by chemical spray technique. The results showed that films of amorphous carbon layer acts as antireflective coatings in solar cells, although it was not possible to find a single material in all ideal conditions for an antireflective layer in crystalline silicon. The silicon carbide wasvery promising as a compound based on carbon and the silicon, been used in the manufacture of the device and abundant in nature (AU)