OPTIMIZATION OF A SCATTERING METALLIC NANOPARTICLES ARRAY TO BE IMPLEMENTED IN ULTRATHIN CIGS BIFACIAL SOLAR CELLS

• Autor(a) principal: Rebola, Pedro Miguel Vilela Pereira Valentim
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/163872
• topic: nanoparticles; plasmonic; light management; thermal dewetting; nanoimprint lithography; FDTD; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

The global energy demand has been increasing, so the development of renewable energy sources is imperative, more specifically, the photovoltaic. One of these technologies is Cu(In,Ga)Se2 (CIGS), and due to the use of scarce materials, the reduction of the absorber layer to the sub-micrometre scale (ultrathin) has been studied. However, this reduction leads to incomplete light absorption and recombination losses at the inter-faces, highlighting the need for light management strategies. Ultrathin bifacial solar cells allow light absorption from both surfaces, providing an additional energy-yield gain, and by integrating light-dispersive metallic nanoparticles (NPs) at the rear interface, this improvement can be even more significant. Finite-difference time-domain optical simulations were performed to study the viability of a plasmonic periodic architecture in an ultrathin CIGS bifacial solar cell. For this purpose, a periodic square array of NPs on an indium tin oxide (ITO) rear contact was optimized, considering two different metallic NPs, Au and Ag, encapsulated with dif-ferent dielectric materials, SiO2, Al2O3, HfO2, and TiO2. From the studied architectures, a NPs’ radius of 80 nm and an interdistance of 150 nm, encapsulated with 10 nm of TiO2, resulted in the best performance for Au and Ag NPs, with a short-circuit current density increase of 6.19 and 6.92 %, respectively. In order to obtain a plasmonic NPs-based architecture with the desired properties, two different approaches were studied. Thermal dewetting of Au thin films was performed for different process conditions, obtaining random arrays of NPs. A study of how the annealing was affecting ITO substrate’s properties was conducted, followed by a process optimization consisting in changing the annealing atmosphere and decreasing ITO’s roughness. On the other hand, a lithographic process based on nanoimprint lithography was also developed and optimized to obtain a periodic square array of NPs, by varying the parameters at different process stages.