Development of Cu(2)ZnSn(S,Se)(4) based solar cells

• Autores: Andrew Fairbrother
• Directores de la Tesis: Edgardo Saucedo Silva (dir. tes.), Alejandro Pérez Rodríguez (dir. tes.)
• Lectura: En la Universitat de Barcelona ( España ) en 2014
• Idioma: inglés
• Tribunal Calificador de la Tesis: Albert Romano Rodríguez (presid.), Lorenzo Calvo Barrio (secret.), Máximo León Macarrón (voc.), Unold Thomas (voc.), Amador Eduardo Pérez Tomás (voc.)
• Materias:
  • Astronomía y astrofísica
    • Sistema solar
      • Energía solar
  • Física
    • Física del estado sólido
      • Semiconductores
  • Química
    • Química analítica
      • Espectroscopia Raman
  • Ciencias tecnológicas
    • Tecnología electrónica
      • Dispositivos fotoeléctricos
• Enlaces
  • Tesis en acceso abierto en:  TDX  Dipòsit Digital de la UB 
• Resumen

  • Thin film solar cell technologies are rapidly developing, and chalcopyrite (Cu(In,Ga)Se2) based devices have demonstrated the highest power conversion efficiencies on the laboratory scale. However, in spite of this promise, there are concerns about the mid- to long-term viability of the material because it contains the relatively scarce elements of indium and gallium. This has led to the development of kesterite (Cu2ZnSn(S,Se)4) based photovoltaic technologies, which is particularly promising because of its similarities with the chalcopyrite material. In this material system indium and gallium are replaced by the more earth abundant elements of zinc and tin. Device efficiencies are still lower than Cu(In,Ga)Se2, but further research and development has led to significant increases in performance in the past few years. To date the device structure and processing parameters for kesterite based devices has been mostly copied from chalcopyrite based technologies. The objective of this thesis is to further develop these kesterite based technologies, and it covers some of the basic challenges related to it, including secondary phase formation and identification, and optimization of the front and back contact areas. Particular emphasis is placed on the deposition and thermal processing of this compound, and how these affect secondary phase formation and device properties. It is based on several articles which explore these in depth. This includes detailed characterization by Raman scattering spectroscopy, x-ray diffraction, scanning electron microscopy, and other techniques. Highlights of the thesis work include: development of a selective chemical etch to remove ZnS, a common secondary phase in this system, which leads to significant improvements in device performance; elaboration of a sulfo-selenization method to form Cu2ZnSn(S,Se)4 from metallic precursors; and understanding the influence of thermal processing parameters on phase formation and distribution