Graphene-ITO hybrid electrodes boost space solar cell conductivity by 60%

Multijunction GaInP/GaAs/Ge solar cells are the dominant photovoltaic technology for space applications, delivering initial efficiencies of around 30% under the AM0 spectrum. These devices rely on stacked p-n junctions with different bandgaps to capture a broader portion of the solar spectrum, but their performance remains constrained by front electrode losses. Transparent conducting oxides such as indium tin oxide (ITO) are widely used, yet they suffer from an inherent trade-off between electrical conductivity and optical transparency, along with mechanical brittleness. To address these limitations, the researchers introduced a hybrid architecture that integrates monolayer graphene with conventional ITO. Graphene, known for its high carrier mobility and optical transparency, was synthesized via cold-wall chemical vapor deposition and transferred onto pre-patterned, commercially available ITO-coated glass substrates (approximately 100 nm thick) using a thermal release tape method. The goal was to enhance lateral conductivity and charge carrier mobility while preserving the transparency required for efficient light absorption in multijunction devices.

Researchers from Italy’s University of Salerno, Warsaw University in Poland and Lithuania’s Center for Physical Sciences and Technology have developed graphene – ITO hybrid transparent electrodes aimed at improving charge transport in next-generation multijunction space solar cells.Multijunction GaInP/GaAs/Ge solar cells are the dominant photovoltaic technology for space applications, delivering initial efficiencies of around 30% under the AM0 spectrum. These devices rely on stacked p-n junctions with different bandgaps to capture a broader portion of the solar spectrum, but their performance remains constrained by front electrode losses. Transparent conducting oxides such as indium tin oxide (ITO) are widely used, yet they suffer from an inherent trade-off between electrical conductivity and optical transparency, along with mechanical brittleness. To address these limitations, the researchers introduced a hybrid architecture that integrates monolayer graphene with conventional ITO. Graphene, known for its high carrier mobility and optical transparency, was synthesized via cold-wall chemical vapor deposition and transferred onto pre-patterned, commercially available ITO-coated glass substrates (approximately 100 nm thick) using a thermal release tape method. The goal was to enhance lateral conductivity and charge carrier mobility while preserving the transparency required for efficient light absorption in multijunction devices.

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