柔性钙钛矿太阳能电池具有柔性、轻量化、低成本和高功率转换效率的特点，在光伏领域极具发展前景。然而，脆性的电极和多晶钙钛矿薄膜限制了柔性钙钛矿太阳能电池的机械稳定性，电池中各层材料间热膨胀系数不匹配、界面处结合力较弱等因素也显著制约了钙钛矿电池的柔性提升，成为其商业化进程的潜在阻碍。本文回顾了近年来柔性钙钛矿电池在衬底、电极、钙钛矿膜层及界面方面重要的柔性改善工作，综述了柔性钙钛矿电池不同功能层的机械稳定性提升策略，并对高效率、机械稳定的柔性钙钛矿电池的未来发展方向进行了初步展望。

All-optical modulators with ultrahigh speed are in high demand due to the rapid development of optical interconnection and computation. However, due to weak photon–photon interaction, the advancement of all-optical modulators is consequently hampered by the large footprint and high power consumption. In this work, the enhanced sensitivity around an exceptional point (EP) from parity-time (PT) symmetry theory is initiatively introduced into a nonlinear all-optical modulator design. Further, a non-Hermitian all-optical modulator based on PT symmetry is proposed, which utilizes the large Kerr nonlinearity from indium tin oxide (ITO) in its epsilon-near-zero (ENZ) region. The whole system is expected to operate around EP, giving rise to the advantages of nanoscale integration and large modulation depth. This presented modulator with high efficiency and high-speed all-optical control can be commendably extended to the design methodology of various nanostructures and further prompt the development of all-optical signal processing.

Optical color filters are widely applied in many areas including display, imaging, sensing, holography, energy harvest, and measurement. Traditional dye-based color filters have drawbacks such as environmental hazards and instability under high temperature and ultraviolet radiation. With advances in nanotechnology, structural color filters, which are based on the interaction of light with designed nanostructures, are able to overcome the drawbacks. Also, it is possible to fabricate structural color filters using standard complementary metal-oxide-semiconductor (CMOS) fabrication facilities with low cost and high volume. In this work, metasurface-based subtractive color filters (SCFs) are demonstrated on 12-inch (300-mm) glass wafers using a CMOS-compatible fabrication process. In order to make the transmissive-type SCF on a transparent glass wafer, an in-house developed layer transfer process is used to solve the glass wafer handling issue in fabrication tools. Three different heights of embedded silicon nanopillars (110, 170, and 230 nm) are found to support magnetic dipole resonances. With pillar height and pitch variation, SCFs with different displayed colors are achieved. Based on the resonance wavelength, the displayed color of the metasurface is verified within the red-yellow-blue color wheel. The simulation and measurement results are compared and discussed. The work provides an alternative design for high efficiency color filters on a CMOS-compatible platform, and paves the way towards mass-producible large-area metasurfaces.

Mono-crystalline silicon solar cells with a passivated emitter rear contact (PERC) configuration have attracted extensive attention from both industry and scientific communities. A record efficiency of 24.06% on p-type silicon wafer and mass production efficiency around 22% have been demonstrated, mainly due to its superior rear side passivation. In this work, the PERC solar cells with a p-type silicon wafer were numerically studied in terms of the surface passivation, quality of silicon wafer and metal electrodes. A rational way to achieve a 24% mass-production efficiency was proposed. Free energy loss analyses were adopted to address the loss sources with respect to the limit efficiency of 29%, which provides a guideline for the design and manufacture of a high-efficiency PERC solar cell.

Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF₄:Yb³⁺/Eu³⁺, a series of NaYF₄:Yb³⁺/Eu³⁺ micro-particles with different Li⁺ doping concentrations were synthesized by the hydrothermal synthesis method, respectively. Firstly, the structure and morphology of NaYF₄:Yb³⁺/Eu³⁺ upconversion micro-particles (UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope (SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li⁺ concentrations of NaYF₄:Yb³⁺/Eu³⁺. X-ray diffraction shows that the crystal field around Eu³⁺ changes with the increase of Li⁺ concentration. Then, the fluorescence spectrum of NaYF₄:Yb³⁺/Eu³⁺ was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF₄:Yb³⁺/Eu³⁺ with 2% Li⁺ is the strongest, which is twice the intensity of NaYF₄:Yb³⁺/Eu³⁺ without Li⁺. Finally, the fluorescence imaging analysis of NaYF₄:Yb³⁺/Eu³⁺ with 2% Li⁺ concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF₄:Yb³⁺/Eu³⁺ (with 2% Li⁺) has great application prospects in anti-counterfeiting recognition.