Hang Ken Lee

Dye-sensitized solar cells with Pt- and TCO-free counter electrodes.

Here for the first time, we demonstrate novel DSSCs with a Pt- and TCO-free counter electrode, which have a highly conductive polymer exhibiting high catalytic ability and charge transport, and the photovoltaic performance increases as we increase the PEDOT film conductivity.

Solution-processable polymer solar cells from a poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acidmethyl ester concentration graded bilayers

Polymer photovoltaic (PV) device prepared with a vertical phase separation has intensified the research on the effectiveness of the concentration graded active layer. In this paper, a polymer PV device with a poly(3-hexylthiophene)/[6,6]-phenyl C61-butyric acidmethyl ester (P3HT/PCBM) bilayers active film with a concentration gradient has been fabricated via solution process. The concentration variation has been confirmed by the Auger spectroscopy. The devices showed an enhanced photocurrent density and power conversion efficiency compared to those of the bulk heterojunction PV prepared under the same fabrication condition.

Two-Dimensional TiO2 Inverse Opal with a Closed Top Surface Structure for Enhanced Light Extraction from Polymer Light-Emitting Diodes

The authors thank Prof. H. Y. Park, Korea Advanced Institute of Science and Technology, and Dr. C.-S. Kee, Advanced Photonics Research Institute, for assistance with the FDTD simulations. This work was supported by an ERC grant of the National Research Foundation of Korea NRF) funded by the Korea Ministry of Education, Science and Technology (MEST) (No. R11–2007-045–01002-0(2009)).

Low vacuum process for polymer solar cells: Effect of TiOx interlayer

Here, the effect of integration of a TiOx interlayer on low vacuum-processible organic-based solar cells is reported. Devices with an Al electrode prepared at a low vacuum condition shows lower efficiency compared to those with an Al electrode prepared at a high vacuum condition because the interface between the active layer and Al electrode is too rough. When a TiOx layer is inserted between the active layer and Al electrode of the device, the cell efficiency is regained and much less dependent on the level of vacuum during Al deposition so that it may be possible to develop low cost process.

Enhanced charge collection via nanoporous morphology in polymer solar cells

We demonstrated a simple and nonlithographic method that enlarges the active layer/metal electrode contact area in polymer solar cells by adding the thermal initiator 2,2′-azobisisobutyronitrile (AIBN) as a nanohole generating agent. From diffused light spectra and x-ray diffraction measurements, it is found that device performance enhancement comes not from a change in the charge carrier generation or transportation characteristics but from increased charge carrier collection due to the reduced contact resistance and shortened pathway to the electrode caused by enlarged interface area.