Nanoporous TiO2 aerogel blocking layer with enhanced efficiency for dye-sensitized solar cells

TiO2 aerogel film possessing nanoporous feature was used as the blocking layer between fluorine-doped tin oxide (FTO) substrate and mesoporous TiO2 layer in dye-sensitized solar cell (DSSC). TiO2 aerogel film was deposited on FTO glass via sol-gel and ambient drying processes and sintered at 500 degrees C, which exhibited the crystallite size of 5-25 nm, the pore size of 3-10 nm, and the thickness of similar to 320 nm. Brunauer-Emmett-Teller (BET) analysis confirmed its nanoporous feature and average pore size of 3.8 nm after annealing at 500 degrees C. In addition, TiO2 aerogel film showed good interfacial adhesion with FTO and mesoporous TiO2 layer, high transmittance over 70% in the visible-near infrared band, and large band gap of 3.67 eV. The DSSC device based on this aerogel blocking layer showed obviously enhanced photocurrent density (J(sc)) and open-circuit voltage (V-oc) compared with the cell without blocking layer. The highest conversion efficiency of 6.0% was achieved for P25 TiO2 mesoporous photoanode based on the aerogel blocking layer, improved by 36% than the control cell. The much decreased recombination frequency (aerogel cell: 11.9 Hz; control cell: 31.5 Hz) observed in Nyquist plots, together with the much prolonged electron lifetime (aerogel cell: similar to 1 s; control cell: 0.02-0.1 s at 0.2-0.55 V) obtained from open-circuit voltage decay curves, indicated that the increased electron life and retarded recombination at FTO/electrolyte interface were primarily responsible for the efficiency improvement in the aerogel blocking layer based DSSC. (C) 2013 Elsevier B.V. All rights reserved.