Development of a lift-off process for sub-micrometer structures implemented on ultra-thin film Cu(In,Ga)Se2 (CIGS) solar cells

• Autor(a) principal: Ribeiro, Rodrigo Miguel M.
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/90815
• topic: CIGS; Solar cells; Optical reflection; Lift-off; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Cu(In,Ga)Se2 (CIGS) solar cells have been gathering increased attention by the scientific and the industrial community, with values of efficiency reaching a record value of 23.35%. Nevertheless, the use of the scarce elements as In and Ga might translate into a higher production cost in the near future. The reduction of the absorber thickness is a solution to this problem. However, some studies point that for sub-micrometer thicknesses, rear contact recombination vastly increases, and the light absorption is incomplete. In order to tackle these problems, several passivation and optical techniques are being developed. The focus of this thesis is to develop a lift-off process for the implementation of a novel structure with the objective of increasing the optical reflection on the rear contact, increasing the optical path. The structure consisted on a metal/dielectric stack patterned with Mo lines that will make the electrical contact with CIGS. Through the use of several metals (Pd, Pt, Cu, Ta) encapsulated with a dielectric layer (SiO2), that were then patterned with Mo lines, using a lithographic step, we managed to enhance both External Quantum Efficiency and the Short Circuit Current (4.13 mA/cm2 abs. increase) on the modified CIGS solar cells, in comparison to an ultrathin reference.