Optimization of RF Magnetron Sputtering of Cerium-Doped Indium Oxide for Silicon Heterojunction Solar Cells

• Autor(a) principal: Magalhães, Maria Meireles Ribeiro
• 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/10362/162023
• topic: SHJ solar cells; TCO; Cerium-doped Indium Oxide; RF magnetron sputtering; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Optimizing solar cell performance hinges significantly on perfecting the Transparent Conduc- tive Oxide (TCO) layer, a critical component for efficient charge collection and light transmis- sion in the solar cell. Due to their high electron mobilities, TCO materials based on In2O3 appear to be particularly interesting options for solar applications. Indium Tin Oxide (ITO) is one of the most well-known and widely used TCO materials, but its performance is hindered by parasitic free carrier absorption and light reflection, particularly in the near-infrared (NIR) spectrum. To overcome these issues, researchers have turned their focus to other doped-indium oxides. This study will focus on optimizing sputtered Cerium-doped Indium Oxide (ICO) for application in Silicon Heterojunction solar cells (SHJ-SC). ICO's wide bandgap, exceeding 3.6 eV, guarantees that a larger fraction of the solar spectrum reaches the silicon absorber layers. Notably, ICO exhibits remarkable electron mobilities, surpassing 130 cm2/Vs when deposited with a heated substrate. However, due to equipment constraints, all depositions in this study were done at room temperature. To elevate ICO's optoelectrical properties, optimization of deposition pa- rameters, such as oxygen flow, chamber pressure, sputtering power, and water vapor partial pressure, was performed. This optimization yielded films with enhanced mobilities and trans- parency, outperforming conventional laboratory-standard ITO films. For a 35-nm-thick ICO layer, we achieved a mobility of 44.22 cm2/Vs, an average trans- mittance of 85.23% and a resistivity of 8.56×10-4 Ω·cm. With the ICO:H layer, we achieved a mobility of 44.56 cm2/Vs, an average transmittance of 84.77%, and a resistivity of 7.28×10-4 Ω·cm. At the device level, we obtained impressive efficiencies of 23.58% and 23.57% for cells employing ICO and ICO:H, respectively. The former showcased a high Voc of 0.722 V, while the latter achieved a Jsc of 40.53 mA/cm2. These results place ICO as a promising alternative for ITO as TCO in diverse photovoltaic applications.