Sung-Yoon Huh

Direct structuring of a biomimetic anti-reflective, self-cleaning surface for light harvesting in organic solar cells.

A one-step method to fabricate a biomimetic dual-scale hierarchical structure for a transparent anti-reflective, self-cleaning layer for organic solar cells is reported. Template-mediated UV replica molding is used to directly create a multi-functional surface with an acrylate-functionalized perfluoropolyether without complicated processing steps. The surface exhibits superhydrophobic properties and self-cleaning characteristics. In addition, the surface leads to an enhancement of photovoltaic power conversion efficiency by ≈10% as a result of reflection suppression and transmittance enhancement. The method can easily be applied to large area substrates (22 cm × 24 cm) in a cost-effective manner. Furthermore, the solar cell can withstand harsh outdoor conditions for a long time, without a notable change in the device performance, owing to robust surface layer and non-fouling properties.

Solution-based formation of multilayers of small molecules for organic light emitting diodes

We developed an approach for fabricating small molecule organic light emitting diodes by solution-based processing. The approach involves dissolving a small molecule organic in a solvent, spin coating it on a mold, and then transferring the layer onto the existing organic layer on a substrate. This ability to form multilayers of small molecule organics allows one to take advantage of both the efficiency offered by the multilayer structures and the low cost fabrication made possible by the solution processing.

Thin pentacene interlayer for polymer bulk-heterojunction solar cell

We demonstrate that introducing a thin pentacene layer between metal cathode and photoactive layer results in a better than 50% improvement in the power conversion efficiency of polymer bulk-heterojunction solar cell when compared with the cell without the interlayer. An additional path for electron transfer provided by the thin pentacene layer appears to be mainly responsible for the improvement along with the increase in the open circuit voltage that occurs with increasing pentacene thickness. The concepts of utilizing additional charge transfer route and exploiting possible change in open circuit voltage with the inserted layer could widen avenues for enhancing the device performance.

Improvement in efficiency of polymer bulk-heterojunction solar cells using modified PEDOT:PSS buffer layers with alcohol derivatives

We demonstrated that the use of modified poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) buffer layers with alcohol derivatives between an electrode and a photoactive layer can lead to the improvement in the efficiency of polymer bulk-heterojunction solar cells. Polymer solar cells containing modified PEDOT:PSS layers show significant improvement in power conversion efficiency by up to ~59% when compared with a device containing only pristine PEDOT:PSS layers. Conformational and morphological changes in the PEDOT:PSS buffer layer corresponding to the dopant polarity and concentration have strong correlations with the surface roughness and arrangement of PEDOT and PSS, which could explain the behaviors of the polymer bulk-heterojunction solar cells with the modified PEDOT:PSS layers.