Advanced Photonics associate editor Dr. Jennifer Dionne interviewed Dr. Harry Atwater, Otis Booth Leadership Chair of the Division of Engineering and Applied Science at Caltech, Howard Hughes Professor of Applied Physics and Material Science, and director of the Liquid Sunlight Alliance.

Low-Earth orbit, the primary operational domain for the international space station and commercial satellites, presents a severe thermodynamic environment for spacecraft. Current testing methodologies, such as thermal cycling and damp-heat assessments, are inadequately aligned with the characteristics of perovskites. The commentary suggests a tiered thermal stress testing framework to enhance existing standards and support a robust and standardized framework for certification.

Lead halide perovskites have started a new era for solar cells. However, the toxicity of lead poses a challenge for their practical applications. Replacing lead with tin provides a feasible way to reduce the toxicity of lead perovskites and can further promote the applications of perovskites. Due to their reduced toxicity with advantageous optical and electronic properties compared to their lead counterparts, tin (II) perovskites (TiPes) have attracted significant interest in recent years, not only for pursuing high-performance solar cells but also in other application fields. We aim to provide a comprehensive overview of recent advances in TiPes, covering fundamental crystal structure, optoelectronic properties, fabrication methods, and applications. A detailed comparison with lead perovskites is included, emphasizing TiPes’ unique strengths while presenting their application challenges. Finally, potential solutions to the challenges are proposed, along with a vision for their future development and potential.

The rapid advancement of renewable energy technologies is essential for combating global climate change and achieving energy sustainability. Among the various renewable sources, solar energy stands out, with silicon playing a pivotal role in solar energy conversion. However, traditional silicon-based devices often face challenges due to high surface reflectance, which limits their efficiency. The emergence of black silicon (b-Si) offers a transformative solution, thanks to its micro- and nanoscale structures that provide ultra-low reflectivity and enhanced light absorption. This makes b-Si an ideal candidate for improving solar energy devices. Beyond solar energy applications, b-Si has drawn notable interest in photonics, including applications in photodetectors, surface-enhanced Raman scattering, and imaging. This review explores b-Si comprehensively, discussing its fabrication processes, distinctive properties, and contributions to both solar energy conversion and photonic technologies. Key topics include its roles in solar cells, photoelectrochemical systems, solar thermal energy conversion, and advanced photonic devices. Furthermore, the review addresses the challenges and future directions for optimizing b-Si to facilitate its practical deployment across a range of energy and photonic applications.

Organic light-emitting diodes (OLEDs) offer advantages for device-integrated transmitters for optical wireless communication because of their simple fabrication, mechanical flexibility, and integration of multiple color devices on a single substrate. However, they are generally considered to be slow due to low charge mobilities. Here, we show they can be made faster by suitable material selection and device design to achieve record-fast transmission by an OLED. We achieve a data rate of 2.9 Gbps in a 10-m data link at a bit error ratio (BER) of 5.54 × 10 - 3, corresponding to a coded data transmission rate of 2.7 Gbps after accounting for 7.15% overhead. This performance is comparable to the previous record for single-OLED transmitters but over a link 40 times longer. In addition, for a 2-m link, we obtain a record data rate of 4.0 Gbps at a BER of 5.54 × 10 - 3 (coded data rate of 3.7 Gbps). Our results show that the operational stability of OLEDs is important for high-speed operation. Thus, with synergetic developments in the stability of OLEDs for displays and lighting industries, OLEDs will become increasingly faster, expanding their applications for spectroscopy, communications, and sensing.

We investigate near-field radiative heat transfer between a current-driven graphene metasurface and an anisotropic magneto-dielectric hyperbolic metamaterial covered with a graphene metasurface according to fluctuational electrodynamics theory. Remarkably, we discover an unconventional radiative cooling flux accompanied by a heating–cooling transition. This phenomenon results from the competition between the high-frequency heating modes and low-frequency cooling modes. Our findings demonstrate a characteristic modulation of radiative heat transfer with implications for efficient thermal management applications.

Almost half of the solar energy that reaches a silicon solar cell is lost due to the reflection at the silicon–air interface. Antireflective coatings aim to suppress the reflection and thereby to increase the photogenerated current. The conventional few-layer dielectric antireflective coatings may significantly boost the transmission of solar light, but only in a narrow wavelength range. Using forward and inverse design optimization algorithms, we develop the designs of antireflective coatings for silicon solar cells based on single-layer silicon metasurfaces (periodic subwavelength nanostructure arrays), leading to a broadband reflection suppression in the wavelength range from 500 to 1200 nm for the incidence angles up to 60 deg. The reflection averaged over the visible and near-infrared spectra is at the record-low level of approximately 2 % and 4.4% for the normal and oblique incidence, respectively. The obtained results demonstrate the potential of machine learning–enhanced photonic nanostructures to outperform the classical antireflective coatings.

Recent progress in the design and fabrication of thermal metasurfaces allows a broad control of the properties of light emission, including its polarization state. Stokes polarimetry is a key approach to accurately characterize partially polarized light. The quality of a Stokes polarimeter made of retarders and polarizers can be evaluated by use of metrics such as the equally weighted variance or the condition number of the matrix representing the polarimeter. Although specific instrument configurations are used to maximize polarimeter performance at a given wavelength, such optimal solutions are not spectrally robust because of the wavelength dependence of retardance. This becomes an issue in characterizing broadband thermal sources in the infrared. We report a Stokes polarimeter making use of five polarization analysis states and consisting of two simple and common optical elements—a crystalline waveplate and a linear polarizer. We combine this setup with a Fourier transform infrared spectrometer to measure accurately in a single set of acquisitions without requiring any spectral filtering, and to measure the polarization state with accuracy over a broad range of wavelengths. Such a Stokes polarimeter allows for close to optimal noise in the data reduction process in the mid-wave infrared spectral range from 2.5 to 5 μm.