Saturday, October 29, 2011
Hall 1-2 (San Jose Convention Center)
Hydrogen treated titanium dioxide (H:TiO2) thin film samples are produced to improve the energy conversion efficiency of open circuit voltage (Voc) and short circuit current (Jsc) of TiO2-nanowire-arrayed dye-sensitized solar cells (DSSCs). An application of hydrogen annealing to DSSCs should increase the efficient charge separation and transportation of TiO2. For hydrogen annealing, hydrothermally-grown TiO2 nanowire arrays on FTO substrates are annealed in air and then hydrogen atmosphere in a CVD system at 550ºC and 320ºC respectively. Commercial N719 and N3 dye (ruthenium, Ru) are used as sensitizers. Modified Pt/FTO glass is used as a counter electrode. When using N3 dye, the optimized TiO2/N3 DSSC produced Voc=0.816V, Jsc=2.75 mA/cm2 and energy conversion efficiency (ƞ)=1.34% while H:TiO2/N3 DSSC produced Voc=0.662V, Jsc=5.64 mA/cm2 and ƞ=1.85%. Hydrogen treatment increased Jsc and reduced Voc, however overall the treatment successfully increased the energy conversion efficiency of DSSC. A similar tendency has been observed in the N719 dye system. This method can also be used in TiO2-thin-film-based DSSC. The surface oxygen-vacancy may increase the recombination rate of electron and hole, which could possibly be the reason why the Voc was reduced. Studies are still being made on the DSSC that examine the electron dynamics, measure the incident-photon-to-current-conversion efficiency (IPCE), and compare adsorption effects of dye between normal and hydrogen treated TiO2 DSSC.