Three-dimensional nanoimprint lithography using two-photon lithography master samples

We demonstrate three-dimensional (3-D) nanoimprint lithography using master samples initially structured by two-photon lithography. Complex geometries like micro prisms, micro parabolic concentrators, micro lenses and other micrometer sized objects with nanoscale features are three-dimensionally fabricated using two-photon lithography. Stamps made out of polydimethylsiloxane are then cast using the two-photon lithographically structured samples as master samples. Hereby, expensive serial nano 3-D printing is transformed into scalable parallel 3-D nanoimprint lithography. Furthermore, the transition from two-photon lithography to imprint lithography increases the freedom in substrate and ink choice significantly. We demonstrate printing on textured surfaces as well as residue-free printing with silver ink using capillary action

Effectively Transparent Front Contacts for Optoelectronic Devices

Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq^(−1). The 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices

Effectively Transparent Front Contacts for Optoelectronic Devices

Effectively transparent front contacts for optoelectronic devices achieve a measured transparency of up to 99.9% and a measured sheet resistance of 4.8 Ω sq^(−1). The 3D microscale triangular cross-section grid fingers redirect incoming photons efficiently to the active semiconductor area and can replace standard grid fingers as well as transparent conductive oxide layers in optoelectronic devices

Effectively transparent contacts (ETCs) for solar cells

We have developed effectively transparent contacts (ETCs) that allow for increased current in heterojunction solar cells. Micro-meter scaled triangular cross-section grid fingers with micro-meter scaled distance redirect light efficiently to the active area of the solar cell and hence, omit losses through reflection at the front finger grid. Furthermore, the grid fingers are placed close together such that only a very thin layer of transparent conductive oxides (TCO) is necessary which avoids parasitic absorption and can decrease material costs. In this paper we experimentally show current enhancement of ~2 mA/cm^2 in silicon heterojunction solar cells using ETCs. 1 mA/cm^2 is gained through less parasitic absorption and 1 mA/cm^2 is gained by efficient redirection of light and therefore, absent shadowing losses

Silicon heterojunction solar cells with effectively transparent front contacts

We demonstrate silicon heterojunction solar cells with microscale effectively transparent front contacts (ETCs) that redirect incoming light to the active area of the solar cell. Replacing standard contact electrodes by ETCs leads to an enhancement in short circuit current density of 2.2 mA cm^(−2) through mitigation of 6% shading losses and improved antireflection layers. ETCs enable low loss lateral carrier transport, with cells achieving an 80.7% fill factor. Furthermore, dense spacing of the contact lines allows for a reduced indium tin oxide thickness and use of non-conductive, optically optimized antireflection coatings such as silicon nitride. We investigated the performance of ETCs under varying light incidence angles, and for angles parallel to the ETC lines find that there is no difference in photocurrent density with respect to bare indium tin oxide layers. For angles perpendicular to the ETC lines, we find that the external quantum efficiency (EQE) always outperforms cells with flat contact grids