EFFICIENT Pt/Sn AND Pt/In COUNTER ELECTRODES FOR FLEXIBLE DYE-SENSITIZED SOLAR CELLS

摘要

In this paper, we use the e-beam evaporation to produce flexible platinum counter-electrodes (CE) which consist of platinum/indium or platinum/tin bi-layer. Introducing In or Sn underlayer can enhance the adhesion of Pt to the substrate and promote the surface topography and porosity of CEs. The experimental results show that the morphology of Pt CE is changed from smooth surface to granular texture when 50-nm-thick underlayer is pre-coated on the PET (100Ω/sq.). The average surface roughness determined from the measurement of AFM is 3.2 nm and 14.7 nm for Pt single layer and Pt/Sn bi-layer, respectively. Results from electrochemical impedance spectra show that the presence of underlayer indeed enhances the adhesion of Pt on PET. The charge transfer resistance (R_(CT)) of Pt/In and Pt/Sn is about 1.2 -1.7 Ω cm~2 which is comparable with that of Pt on TCO glass, whereas the R_(CT) of single Pt on PET is undeterminable due to the instability of Pt on PET. The current-voltage characteristics of DSSC with Pt/Sn (In)/PET CE reveal a V_(OC) of 0.7- 0.80 V, J_(SC) 9.3 -10.9 mA/cm~2, fill factor 0.68-0.78, and cell efficiency 5-6% under AM1.5 illumination at 100 mW/cm~2. Performance of DSSC has been improved by approximately 30% when the platinized CE was coated on 50-nm-thick Sn or In buffer layers.