Some application cases and related manufacturing techniques for optically functional microstructures on large areas

Abstract

With surface-relief structures, optical functions that are required for radiation power management such as antireflection, light trapping, or light distribution and redirection can be obtained for new applications in solar energy systems and in displays. There, structures with submicrometer features must be distributed over large areas homogeneously. We address the design and the whole experimental process chain from the microstructure origination on large areas to the replication and the system integration in the specific application. Topics are antireflective surfaces for solar systems and displays, light trapping in polymer solar cells, sun protection systems for facades, and diffusers for projection displays and in glazing. For the microstructure origination we investigate the suitability of holographic recording in photoresist using a large-scale interferometer. We use an argon ion laser as a coherent light source at a wavelength of 364 nm. Periodic and stochastic interference patterns are recorded in positive photoresist with the interferometer setup. In the case of periodic structures, grating periods between 200 nm and 20 µm are realized. By carefully modeling the resulting resist profiles it is possible to originate even prismatic surface-relief profiles. Structures with good homogeneity are originated on areas of up to 4800 cm2 by optimizing the interferometer setup and the photoresist processing

Magnetization Reversal in Ferromagnetic Films Patterned with Antiferromagnetic Gratings of Various Sizes

“…Ta ð5 nmÞ=Ni 80 Fe 20 (10 nm) is deposited on top of a Si wafer using triode sputtering at 2 × 10 −8 Torr base pressure and 1 m Torr Ar pressure with a growth rate of 0.132 nm s −1 . A grating pattern mask is then fabricated on the NiFe using interference lithography [21]. A trilayer stack of antireflective coating (ARC) ð315 nmÞ=SiO 2 ð20 nmÞ=PS4 negative resist (Ohka) (215 nm) is first deposited, as shown in the schematic in Fig.…”

Rear Side Diffractive Gratings for Silicon Wafer Solar Cells

“…When it comes to the fabrication of periodic (but also aperiodic) patterns on large areas, one technology of choice is interference lithography (IL) [92]. In IL, a laser beam is split into two or more beams, which are expanded and superimposed on a photoresist coated sample (see Figure 3.13).…”

Nanoimprint lithography for solar cell texturisation

“…Beyond this process chain for texturisation, the integration into the solar cell fabrication has also to be considered. Interference lithography was chosen as the mastering technology within this work, because it allows the origination of surface reliefs with a wide range of feature sizes from 100 nm to 100 µm on large areas [124]. This technology is particularly suited for periodic features, as are dealt with in chapter 5, but can also be used to achieve non-periodic patterns.…”