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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.

One of the main challenges for highly sensitive surface-enhanced Raman scattering (SERS) detection is the noise interference of fluorescence signals arising from the analyte molecules. Here we used three types of gold nanostars (GNSs) SERS probes treated by different surface modification methods to reveal the simultaneously existed Raman scattering enhancement and inhibiting fluorescence behaviors during the SERS detection process. As the distance between the metal nanostructures and the analyte molecules can be well controlled by these three surface modification methods, we demonstrated that the fluorescence signals can be either quenched or enhanced during the detection. We found that fluorescence quenching will occur when analyte molecules are closely contacted to the surface of GNSs, leading to a ~100 fold enhancement of the SERS sensitivity. An optimized Raman signal detection limit, as low as the level of 10−11 M, were achieved when Rhodamine 6 G were used as the analyte. The presented fluorescence-free GNSs SERS substrates with plentiful hot spots and controllable surface plasmon resonance wavelengths, fabricated using a cost-effective self-assembling method, can be very competitive candidates for high-sensitive SERS applications.

A poly-L-lysine assisted self-assembly method based on the surface chemistry of silica microspheres and the textured polycrystalline silicon solar cell surface is proposed in this article. With four-step solution-based processes, silica microspheres are deposited tightly on the surface of the device, acting as an anti-reflection layer. By tuning the assembly time, uniform distributions of silica microspheres with varying density can be achieved. Furthermore, the electrical tests show a maximum relative efficiency enhancement of 9.35% with solar cell area of 2 cm * 2 cm under AM1.5 illumination. Optical micrographs and reflection spectra are used to further characterize the light-trapping properties of silica microspheres. This strategy may pave the way for large-area and cost-effective assembly of silica spheres or silica coated nanoparticles on different substrates for solar energy harvesting applications.

The effect of plasmon-induced hot carriers (HCs) enables the possibility of applying semiconductors with wide band gaps to visible light catalysis, which becomes an emerging research field in environmental protections. Continued efforts have been made for an efficient heterostructure photocatalytic process with controllable behaviors of HCs. Recently, it has been discovered that the improvement of the utilization of HCs by band engineering is a promising strategy for an enhanced catalytic process, and relevant works have emerged for such a purpose. In this review, we give an overview of the recent progress relating to optimized methods for designing efficient photocatalysts by considering the intrinsic essence of HCs. First, the basic mechanism of the heterostructure photocatalytic process is discussed, including the formation of the Schokkty barrier and the process of photocatalysis. Then, the latest studies for improving the utilization efficiency of HCs in two aspects, the generation and extraction of HCs, are introduced. Based on this, the applications of such heterostructure photocatalysts, such as water/air treatments and organic transformations, are briefly illustrated. Finally, we conclude by discussing the remaining bottlenecks and future directions in this field.

The tunable and amazing properties of plasmonic nanostructures have received significant attentions in the fields of solar energy conversion. Plasmonic nanostructures provide pathways to directly convert solar energy into electric energy by hot-carrier generation. They can also serve as economical electrodes for high-efficient carrier collection. Both have promising potential for manufacturing new generation solar cells. Here, we review recent advances in plasmonic nanostructures for electronic designs of photovoltaic devices and specially focus on plasmonic hot-carrier photovoltaic architectures and plasmonic electrode structures. Technical challenges toward low-cost and high-performance plasmonics-based solar cells are also discussed.