Structure and properties of oxide semiconductors modified by redox-active molecules, formation of heterojunctions with novel organic electronic materials

• Research unit: COST
• Project number: C99.0048

Key words (English)

Mesoscopic semiconductor films; lithium ion insertion; rocking chair intercalation batteries; sensitized solid state heterojunctions

Research programs (English)

COST-Action D14 - Functional Molecular Materials

Short description (English)

See abstract

Partners and International Organizations (English)

A, B, CZ, DK, FIN, F, D, GR, H, IRL, I, NL, PL, P, E, CH, TR, GB

Abstract (English)

The photovolatic performance of solar cells based on solid state sensitized heterojunctions was improved from 2.5 to 3.2 % overall conversion efficiency in full sunlight by facilitating the self assembly of the ruthenium charge transfer sensitizer through the addition of silver ions. The enhancement in overall device efficiency is a result of increased open circuit voltage and short circuit current. Spectroscopic analysis shows that the silver binds to the thiocyanate via the amphidentate thiocyanate ligands bridging adjacent dye molecules and increasing in this manner the packing density of the sensitizer on the surface. Work on lithium insertion dynamics in mesoscopic oxide has also progressed well. Electrodes from nanocrystalline Li4Ti5O12 were found to exhibit excellent activity towards Li-insertion, even at charging rates as high as 250°C. The charge capability at 50°C-250°C was proportional to the logarithm of surface area for coarse particles (surface areas smaller than ca. 20 m2/g). With increasing charge/discharge rates, a narrowing plateau in performance was observed for materials with surface areas between ca. 20 to 100 m2/g. These materials can be charged/discharged nearly to the nominal capacity of Li4Ti5O12 (175 mAh/g) within a wide range of the rates. The optimum performance of thin-film Li4Ti5O12 is achieved, if the parent materials have surface areas between ca. 20 to 110m2/g, with the maximum peak at 110 m2/g.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C99.0048