arXiv subjects

Alexander Veber

Publications and source records attributed to Alexander Veber.

3 recordsLinked to original sources

arXiv2026

THz near-field nanoscopy employing coherent synchrotron radiation

We demonstrate that the coherent synchrotron radiation (CSR) can be used for the scattering type near-field scanning optical microscopy (s-SNOM). Using a commercially available s-SNOM coupled to a synchrotron source we perform THz imaging and spectroscopy experiments in the spectral range of 25-55 cm-1 and spatial resolution of 60 nm. It is shown that the same optical configuration can be used for nanoscopy in the range of 25 to 4000 cm-1. Conducting experiments across the THz, far-, and mid-IR spectral ranges within a single setup offers a unique capability for the ultrabroadband characterization of complex materials in both life and material sciences at the nanoscale.

physics.optics↗

arXiv2025

CsCl seed layer homogenizes co-evaporated perovskite growth for high-efficiency fully textured perovskite-silicon tandem solar cells

Monolithic perovskite-silicon tandem solar cells experienced a significant increase in efficiency, making them viable for industrial applications. Among the various scalable and industry-compatible metal halide perovskite deposition techniques, co-evaporation stands out as particularly well-suited for perovskite-silicon tandem solar cells due to its ability to conformally cover textured silicon bottom cells. Solution-processed [2-(3,6-Dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) is commonly used as a hole-transporting material for co-evaporated metal halide perovskites. However, we show that it covers the textured surface of silicon bottom cells unevenly, impacting the film growth and leading to the formation of residual PbI2 at the buried interface. The present study reveals via X-ray photoemission electron microscopy (XPEEM) and infrared scattering-type scanning near-field optical microscope (IR s-SNOM) that a CsCl seed layer fosters organic precursor incorporation across the MeO-2PACz/perovskite interface, even in the areas with a thin MeO-2PACz layer, thereby preventing the formation of interfacial PbI2 and leading to larger apparent grains. The improvement of the metal halide perovskite film quality on the MeO-2PACz/perovskite interface and the bulk perovskite film led to 30.3% (29.7% certified) efficient perovskite-silicon tandem solar cell. The present work highlights the importance of a seed layer for a robust growth of co-evaporated metal halide perovskite and represents an important milestone for the transfer of perovskite-silicon tandem solar cells from laboratory to industry.

cond-mat.mtrl-sci↗

arXiv2024

Infrared spectroscopy across scales in length and time at BESSY II

The infrared beamline at BESSY II storage ring was upgraded recently to extend capabilities of infrared microscopy. The end-stations available at the beamline are now facilitating improved characterization of molecules and materials at different length scales and time resolution. We report the current outline of the beamline and give an overview of the end-stations available. In particular, presented here are first results obtained with using a new microscope for nano-spectroscopy that was implemented. We demonstrate the capabilities of the scattering-type near-field optical microscope (s-SNOM) by investigation of cellulose microfibrils, representing nanoscopic objects of a hierarchical structure. It is shown that the s-SNOM coupled to the beamline allows to perform imaging with spatial resolution less than 30 nm and to collect infrared spectra from effective volume of less than 30x30x12 $nm^3$. Potential steps for a further optimization of the beamline performance are discussed.

physics.optics↗