The electron transport adn back reactin in nanocrystalline iO_2 films prepared at low temperataur using a new hydrothermal crystallization method on conductive glass and plastic substrates have bene investigated by intensity modulated photocurrent sjpectroscopy (IMPS)and intensity modulated photovoltage spectroscopy (IMVS).The hydrothermal method enables the preparation of crack-free TiO_2 thick films and at the same time enhanced the electron transport compared to films perpared by ow-temperatures sintering,providing a path towards efficient photoelectrode materials for flexible dye-sensitized solar cells.UV/ozone treatment of the films enables the removal of residual orgainics left from the hydrothermal preparation process.Since these organice represent surface states that mediate the back reactin of electrons,the electron lifetime is increasedby their removal,while the electron transport is not enhanced signifiantly.High-temperataue sintering of te hydrothermally perpared rilms laeads to both a removal of the surface states and a significant enhancement o the electron trasnport properties.Interestingly,the electron lifetimes are not changed by hgih-tempearature sintering,since aster electron transpot and less surface states have opposite effects on the back reaction process.,These films showed improved electron transpor tproperties and efficiencies even if compared with films pepared by conventional high-temperature methods,which shows the high potential for the further development of the hydroethermal method.
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