Study On The Dye-sensitized Solar Cell Based On Graphene And Quantum Dots

On the circumstance of serious energy problems and environmental pollutions,seeking new, clean and renewable energy resources for replacing conventional fossilfuels has motivated the interest. Solar energy is inexhaustible, renewable, safe andeffective, and has become one of the most important research hotspots to solve theenergy crisis, while solar cell is the most important and effective way to use solarenergy. Dye-sensitized solar cell （DSSC）, since the seminal paper by O’Regan andGr tzel in1991, has been one of the most promising candidates for conventionalsilicon solar cell because of low cost, simple preparation, relatively high efficiency.Although a DSSC with light-to-electric energy conversion efficiency of12%has beenachieved, it is still a crucial issue to enhance its efficiency.Graphene, a two-dimensional nanocarbon material, has showed considerablepromise in photovoltaic field due to its unique physical and chemical properties.Especially, because of high electron mobility and large theoretical specific surfacearea of graphene, it has aroused intensive interest in the application of DSSC. Toimprove the performance of photoanode, a graphene/TiO₂composite was prepared byone-step hydrothermal method and was introduced into photoanode of DSSC, it isexpect that the photovoltaic performance can be improve due to its unique properties.The composite was also used to fabricate photoanode of CdS quantum dots sensitizedsolar cell （QDSSC）. On the other hand, in view of the present CdS QDSSC efficiencyis very low, the modification of the dye is used to improve the energy conversion ofCdS QDSSC. The experiment content and results are as follows:（1） The improved Hummers’ method was used to prepared graphite oxide, andthen a mixed colloid of graphene and TiO₂was prepared by one-step hydrothermalmethod. At the hydrothermal process, the graphene/TiO₂composite was achieved.The graphene/TiO₂（RGT） photoanode of DSSC was fabricated by employing themixed colloid. The results indicates that the RGT film possesses high porosity andspecific surface area, thus can absorb more dye molecular. Meanwhile the RGT filmcan boost the electron transport and suppresses the charge recombination. Under an optimal condition, the short-circuit current density and the energy conversionefficiency of the DSSC based on RGT film are14.37mA·cm2and7.52%, which isincreased by21%and17.7%, respectively, compared with the cell based on thepristine titania electrode under a simulated solar light irradiation of100mW·cm2.（2） The RGT film was used to assemble CdS QDSSC, the results shows that theRGT film can favor the deposition the CdS QDs on the film and the RGT film canalso accelerate electronic transportation and suppress the charge recombination.Under an optimal condition, the short circuit-current density and conversionefficiency of the CdS QDs-sensitized solar cell based on graphene/TiO₂photoanode is7.19mA·cm2and1.70%, increasing by51%and57%, respectively, compared withthe cell based on the pristine TiO₂electrode under a simulated solar light irradiationof100mW·cm2.（3） The CdS quantum dot-sensitized TiO₂film was prepared by the successiveionic layer adsorption and reaction （SILAR） technique, and then the film wasmodified by the dye to prepared photoanode of QDSSC. The results suggests that themodification of the dye can extend the spectral response of CdS QD sensitizedelectrode. Meanwhile the TiO₂/CdS/dye electrode can suppress the recombination ofphoto-induced electrons and holes and increases the electron lifetime due to dye canscavenge holes from the CdS QD. Consequently, the short-circuit current density andconversion efficiency of the cell with TiO₂/CdS/dye are increased by77%and117%,respectively, compared with the cell with CdS under a simulated solar light irradiationof100mW·cm2.