Tom Veeken

As of September 2022, I am the Program Manager of the Light Management in new Photovoltaic Materials (LMPV) program at AMOLF. In this novel role, I work with the group leaders and researchers in the LMPV program to improve our organization across the board, for example regarding internal communication and hiring, research equipment and collaborations, and knowledge transfer.

After having defended my PhD thesis in May 2022, I am also a part-time Postdoc in the Photonic Materials group, led by Prof. Albert Polman, at AMOLF (Amsterdam, The Netherlands). My work focuses on the theory, fabrication, and optical characterization of photonic nano- and microstructures for solar cells and optoelectronic devices.

Light management for optoelectronic devices at the nanoscale

Optoelectronic devices are found in a very large number of customer markets today. These devices either absorb light and convert it into electricity (solar cells, photodetectors), or they emit light by using electricity (LEDs, displays). Improvements in material quality and device processing have resulted in a consistent increase in efficiency in these devices over the past years. It is now being realized that to these efficiencies can be increased even further by tailoring the surfaces and interfaces of these devices. These novel surfaces and interfaces have textures with features down to the nanometer scale, much smaller than the conventional micrometer-scale designs.

Using nanotextures, the optical response can be improved, but also becomes more complex. Traditionally, light-matter interaction, at the micron-scale and larger, is easily calculated using ray-optics, which is readily available at the industry level. In the ray-optics picture, the wavelength of the light is assumed to be much smaller than the features of the material, and therefore the light propagation is described by light rays. The light rays always travel in linear directions, and have a certain probability to reflect or transmit at an interface. Absorption of light rays occurs according to a fixed probability per unit length. The ray optics model explains reality very well for macroscopic geometries, but when the features of the materials become much smaller than the wavelength, the model breaks down. Instead, light propagation must be described by light waves. In the wave-optics picture, light is described by a wavelength and a propagation phase, which allows for interference between waves. The interference can be constructive or destructive, and as a result the light intensities can vary over distances much smaller than the wavelength. This, in turn, has a major effects on reflection, absorption, and transmission of light.

Numerical wave-optics simulations

To calculate the propagation in the wave-optics model, one needs to solve Maxwell’s equations at the nanoscale. For regular materials, this can be done analytically. However, for irregular systems such as the nanotextures in optoelectronic devices, this needs to be done with a numerical simulation. Here, the material is modeled by a 3D grid of very small (a few nanometer) cells and Maxwell’s equations are solved to calculate the light fields in each cell using an iterative procedure. The calculations in the wave-optics model are mathematically more involved than those for the ray-optics model and require powerful computer hardware. We have studied the application and validity of analytical models in a recent paper [2], using our numerical wave-optics simulations as a benchmark.

Get in touch with me through the following links: 

Google Scholar
Light Management in new Photovoltaic Materials research at AMOLF

Scientific publications:

  1. Two-step sputter-hydrothermal synthesis of NaTaO3 thin films
    L. Polak, T. Veeken, J. Houtkamp, M.J. Slaman, S.M. Kars, J.H. Rector, and R.J. Wijngaarden, Thin Solid Films, 603 (2016)
  2. Application and validity of the effective medium approximation to the optical properties of nanotextured silicon coated with a dielectric layer
    T.H. Fung, T. Veeken, D. Payne, B. Vettil, A. Polman, and M. Abbott, Optics Express 27, 38645 (2019)
  3. Photovoltaics reaching for the Shockley-Queisser limit
    B. Ehrler, E. Alarcon Llado, S.W. Tabernig, T. Veeken, E.C. Garnett, and A. Polman, ACS Energy Lett. 5, 3029 (2020)
  4. Unlocking Higher Power Efficiencies in Luminescent Solar Concentrators through Anisotropic Luminophore Emission
    J.S. van der Burgt*, D.R. Needell*, T. Veeken*, A. Polman, E.C. Garnett, and H.A. Atwater, ACS Appl. Mater. Interfaces 13, 40742 (2021)
  5. Directional quantum dot emission by soft-stamping on silicon Mie resonators
    T. Veeken, B. Daiber, H. Agrawal, M. Aarts, E. Alarcón-Lladó, E.C. Garnett, B. Ehrler, J. van de Groep, and A. Polman, Nanoscale Adv. 4, 1088 (2022)
  6. Plasma Focused Ion Beam Tomography for Accurate Characterization of Black Silicon Validated by Full Wave Optical Simulation
    Y. Zhang, T. Veeken, S. Wang, G. Scardera, M. Abbott, D.N.R. Payne, A. Polman, and B. Hoex, Adv. Mater. Technol. 7, 2200068 (2022)
  7. Passive Radiative Cooling of Silicon Solar Modules with Photonic Silica Microcylinders
    E. Akerboom*, T. Veeken*, C. Hecker, J. van de Groep, and A. Polman, ACS Photonics 9, 3831-3840 (2022)

Conference presentations:

* equal contribution