The need for free-form micro-optics (FFMO) is constantly growing in well-established business segments including flatpanel displays, solid-state illumination, thin-film solutions for security/anti-counterfeiting applications, AR/VR wearables, and automotive headlights. However, the high access barriers to pre-commercial production capabilities prevent companies, especially SMEs, from exploiting the FFMO technology in commercial products and hinder further innovation. To lower the barrier to access FMOA technology, CSEM and their partners have established the PHABULOuS Pilot Line. PHABULOuS offers a unique one-stop shop for all requests for prototyping and manufacturing of free-form microoptics services, from pilot to full-scale production. To mature the FMOA technology, the Pilot Line members have developed high precision origination techniques complemented by industry-fit, high-throughput up-scaling technologies for the cost-effective production of large-area FFMO. At the core of these technologies is Step & Repeat UV imprinting. The method has been successfully demonstrated in the PHABULOuS project for high precision upscaling of rigid small masters to flexible tools with 600 x 300 mm2 dimensions using a standard UV-NIL stepper modified for this purpose. Since there is currently no commercial Step & Repeat machine on the market able to replicate free-form micro-structures on large area with the required precision, CSEM has developed a high precision S&R UV-replication platform designed specifically to this purpose. Combined with the expertise in design and optical simulation, origination, and electroforming, the newly developed Step&Repeat capabilities at CSEM will strengthen the PHABULOuS Pilot Line offerings.
Freeform micro-optical arrays (FMOAs) can overcome some limitations of rotationally symmetric optical components. The manufacturability assessment for FMOA designs containing many freeform elements is demanding. We present computer-aided design (CAD) tools that analyze FMOA designs for manufacturing constraints. They 1) extract the height (Sag) and 2) local slope while highlighting areas beyond manufacturing limits, 3) extract the minimum tool radius and 4) convert CADs into ray traceable solids using NURBS for performance comparison of the actual micro-structure to the design. Critical parameters can be identified early, reducing time-consuming and costly adjustments later.
Photonics integration continues to be a main driver for innovation in multiple aspects, including wafer-scale integration, new materials, sub-micron alignment of components and protection from harsh environment. We show cost-effective fabrication technologies of micro-optical components by UV wafer-scale replication into chemically stable polymers. Furthermore, for simplified fiber coupling and packaging, a novel 90° optical interconnect is presented, integrated with self-alignment structures. Replicated, space compliant microlenses on packaged CMOS imagers show improved light sensitivity by a factor 1.8. A laser based, low stress bonding process is explored to generate wafer-scale hermetic enclosures for harsh environment applications ranging from space to implants.
Monte Carlo simulations are used to investigate the dissociation of a Coulomb correlated charge pair at an idealized interface between an electron accepting and an electron donating molecular material. In the simulations the materials are represented by cubic lattices of sites, with site the energies spread according to Gaussian distributions. The influence of temperature, applied external fields, and the width of the Gaussian densities of states distribution for both the electron and the hole transporting material are investigated. The results show that the dissociation of geminate charge pairs is assisted by disorder. When the rate for geminate recombination at the interface is very low (<1 ns-1) the simulations predict a high yield for carrier collection, as observed experimentally. Comparison of the simulated and experimentally observed temperature dependence of the collection efficiency indicates that at low temperature dissociation of the geminate charge pairs may be one of the factors limiting the device performance. Furthermore, the simulations show that excess exciton energy liberated in the photoinduced charge transfer process enhances dissociation of the geminate pair and can thereby allow for high yields for carrier collection.
The photophysical properties of a solution processed blend of two semiconducting polymers with electron donating and electron accepting properties, respectively, as used in polymer photovoltaic devices have been investigated. In the binary mixture of poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly[oxa-1,4-phenylene-(1-cyano-1,2-vinylene)-(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylene)-1,2-(2-cyanovinylene)-1,4-phenylene] (PCNEPV) photoexcitation of either one of the polymers results in formation of a luminescent exciplex at the interface of the two materials. The high energy of this correlated charge-separated state is consistent with the high open-circuit voltage of the corresponding solar cells (1.36 eV). Application of an electric field results in dissociation of the marginally stable exciplex into charge carriers, which provides the basis for the photovoltaic effect of this combination of materials.
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