CsPbIBr₂, a cesium-based all-inorganic halide perovskite (CsPe), is a very promising alternative material to mainstream organic–inorganic hybrid halide perovskite (HPe) materials owing to its exceptional moisture stability, thermal stability, and light stability. However, because of the wide band gap (2.05 eV) of CsPbIBr₂, it has a low power conversion efficiency (PCE), which hinders its application in highly efficient solar cells. In this study, a facile nanoimprinted one-dimensional grating nanopattern (1D GNP) formation on mesoporous TiO₂ (mp-TiO₂) photoelectrodes was introduced to improve the effective light utilization and enhance the performance of CsPbIBr₂ perovskite solar cells (PSCs). The 1D GNP structure on the mp-TiO₂ layer increases the light absorption efficiency by diffracting the unabsorbed light into the active mp-TiO₂ and CsPbIBr₂ layers as well as increasing the charge separation and collection due to the extended interfacial contact area between the mp-TiO₂ and CsPbIBr₂ layers. Consequently, both the current density (J_SC) and the fill factor (FF) of the fabricated cells improved, leading to over a 20% enhancement in the solar cell’s PCE. Thus, this periodic grating structure, fabricated by simple nanoimprinting, could play an important role in the large-scale production of highly efficient and cost-effective Cs-based PSCs.

We propose an optimized structure for a humidity-sensing colorimetric sensor that utilizes a metal-organic framework to form a one-dimensional photonic crystal. The structure changes spectral reflectivity by switching its photonic band gap (PBG). We found that, although photonic crystals on a highly-reflective substrate increased the peak more than a transparent substrate, the resulting ripples in the wavelength band near the PBG destroy our ability to detect the color conversion. We also show that, despite the blue-shift of the peak PBG wavelength for higher angles of incidence, our sensor can still create significant color conversion at nonzero angles when the environmental humidity changes. Therefore, photonic crystals on a transparent substrate that utilize PBG-switching can operate as moisture-sensitive colorimetric sensors. Our study will help optimize sensors and industrial nano-structures.

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se₂ (CIGS) solar cells with a grating aluminum oxide (Al₂O₃) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al₂O₃ is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 μm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al₂O₃ insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results.

Structural colors have been reported instead of conventional dye- or pigment-based color filters. Color selectivity can degrade as structure-based optical resonances are accompanied by several resonance modes. In this work, we suggest a simple and effective design of the plasmonic color filter (PCF) that integrated the PCF with the one-dimensional (1D) photonic crystal (PhC). The introduced PhC creates an optical band gap and suppresses undesired peaks of the PCF caused by the high-order resonance mode. Finally, the suggested structure provides a high color purity. This study can be a guideline for technology that replaces conventional color filters.