van der Groep, and David Valley for useful discussions and assistance with the manuscript. The Caltech portion of this work was supported by the Department of Energy under contract number DE-FG02-07ER46405 (modeling) and SETP GO-18006 (cell fabrication). Work at AMOLF is part of the research program of FOM that is financially supported by NWO. This work is also part of the Global Climate and Energy Project (GCEP).

We present a generic approach for the optimization of light-trapping patterns for thin-film solar cells. The optimization is based on tailoring the spatial frequencies in the light-trapping pattern to the waveguide modes supported by the thin-film solar cell stack. We calculate the dispersion relations for waveguide modes in thin-film Si solar cells and use them to define the required spatial frequency band for light trapping. We use a Monte Carlo algorithm to optimize the scattering power spectral density (PSD) of a random array of Mie scatterers on top of a-Si:H cells. The optimized particle array has a PSD that is larger in the desired spatial frequency range than the PSD of a random array and contains contributions at more spatial frequencies than the PSD of a periodic array. Three-dimensional finite-difference time-domain simulations on thin-film solar cells with different light-trapping patterns show that the optimized particle array results in more efficient light trapping than a random array of Mie scatterers. We use the same approach to design a random texture and compare this to the Asahi-U-type texture. We show that the optimized texture outperforms the Asahi-U pattern and an optimized periodic pattern. The light-trapping patterns presented avoid the ohmic absorption losses found in metallic (plasmonic) patterns. They can be tailored to specific spatial frequency ranges, do not contain materials that are incompatible with high-temperature processes, nor require patterning of the active layer. Therefore, they are applicable to nearly all types of thin-film solar cells.

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Due to the high energy of extreme ultraviolet (EUV) photons, stochastic effects become more important at a constant dose when compared with deep ultraviolet exposures. Photoresists are used to transfer information from the aerial image into physical features and play an important role in the transduction of these stochastic effects. Recently, metal-oxide-based nonchemically amplified resists (non-CARs) have attracted a lot of attention. We study how the properties of these non-CARs impact the local critical dimension uniformity (LCDU) of a regular contact hole array printed with EUV lithography using Monte Carlo simulations and an analytical model. We benchmark both the simulations and the analytical model to experimental data, and then use the flexibility of both methods to systematically investigate the role of microscopic resist properties in the final LCDU. It is found that metal-oxide clusters should be <1 nm in diameter, otherwise granularity will have a significant contribution to LCDU. When varying resist properties to change the resist dose-to-size, we find that the LCDU scaling with dose depends on how the resist is modified. After performing an overall sensitivity analysis to identify the optimum scaling of LCDU with dose, we find a scaling of dose −0.5 when the development threshold is modified, and a scaling of dose −0.33 when core radius or the quantum efficiency is changed.