From macro to micro: multi-scale study of plasmonic nanocoating self-assembled on multijunction bulk solar cells

Nanophotonics pours into new opportunities to achieve ultrahigh-efficiency solar cells, attracting tremendous interests from photovoltaic research and industry. Plasmonic nanostructures, enabling strong light-matter interaction at the nanoscale, have been widely used for efficiency enhancement in thin-film solar cell devices based on plasmonic near-field effects. Unlike thin-film device cases, we found forward scattering and inter-particle coupling engineering of subwavelength plasmonic nanostructures are the key to enhance the efficiency of bulk multijunction solar cells (MJSCs). As a proof of concept, we studied the plasmonic enhancement of Ag@SiO2 nanocoating self-assembled on InGaP/GaInAs/Ge MJSCs at both macro and micro scales. From the macro measurements, the experimental enhancement of Ag@SiO2 core-shell nanostructure could be well-matched with the simulational results, where strong forward scattering and suppressed interparticle coupling could be simultaneously achieved by employing ~ 22 nm SiO2 shell layer. Using a double excitation method under an infinity optical microscope, we directly observed multi-wavelength uniform photocurrent enhancements on MJSCs at a submicrometer scale. This study will provide an effective strategy and opening up new opportunities to explore high-efficient MJSCs using nanophotonics.