| 학회 | 한국고분자학회 |
| 학술대회 | 2005년 가을 (10/13 ~ 10/14, 제주 ICC) |
| 권호 | 30권 2호 |
| 발표분야 | 자기조립형 기능성재료 |
| 제목 | Fabrication and application of nanowires using the block copolymer nanoporous template |
| 초록 | There have been extensive studies on photovoltaic devices based on organic and polymeric PN heterojunction materials because of the ease of processing, low cost of fabrication, and flexibility of the films. However, the power conversion efficiency (ηp) of these devices is only ~2 %, much less than crystalline silicone(~ 24 %) and thin amorphous silicone films (~17 %). These lower efficiencies arise from the fact that free electrons and holes are not directly produced by photon absorption in the organic or polymer materials. Rather, electron-hole pairs (excitons) are created, and dissociate into holes and electrons. Exciton dissociation in heterojunction photovoltaic (PV) devices occurs mainly at the interface of the hole (P-type conducting polymer) and electron acceptor (N-type conducting polymer). Two different PN-heterojunction PV device geometries have been reported: bilayer laminated films of P-type/N-type conducting polymers, and single-layered film where P-type/N-type conducting polymers phase separate into bicontinuous interpenetrating network (IPN) structures. Although the P-N contact for the single-layered IPN structures is much larger than that for bilayerd geometry, the hole and electron transport to the collection electrodes for the IPN structures is much less, since some electrons cannot cross the hole acceptor barrier unless all of the electron-acceptor domains are connected to the electrode. The maximum diffusion length for excitons before their disappearance is ~ 20 nm; therefore the distance between P-type and N-type materials should be less than 20 nm. Also, all of the hole- and electron- acceptor domains should make contact to their respective electrodes (ITO) coated glass for holes and aluminum for electrons). Here, we show that nanoporous templates made from polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) satisfy these two criteria. Previous studies have shown that arrays of nanoscopic cylindrical microdomains oriented normal to the surface of the film can easily be prepared. By removal of one of the components of PS-b-PMMA or of added homopolymer, nanoporous films are produced with areal density of pores even greater than that of AAO membranes. Not only can the templates be prepared on rigid supports but also on flexible substrates. In addition, upon removal of the matrix polymer, the configuration of the nanowires was preserved, which is a necessary step for the introduction of device fabrication. Block copolymer templates are used to fabricate high-efficiency PV devices. After the removal of the PS matrix, the highest occupied and the lowest unoccupied molecular orbitals (HOMO and LUMO, respectively) of Ppy, PEDOT or P3HT were essentially the same as those of the pure polymers. Since the N-type material can easily be spin-coated onto this array, a simple route is shown for the preparation of PV devices with high conversion efficiency. |
| 저자 | 이정인1, 김진곤1, 장정아1, 유재웅2, 박정환2 |
| 소속 | 1포항공과대, 2한국과학기술(연) |
| 키워드 | nanowires; blockcopolymer nanoporous tempalte |
