Preparation And Photoelectric Performance Of TiO₂-based Mesoscopic Solar Cells

Solar cells,which can convert solar energy into electricity directly,are considered very promising to address the issue of energy shortage nowadays.Among them,mesoscopic solar cell?MSC?has been extensively studied because of its unique mesoporous structure.Mesoscopic structure possesses larger specific surface area,leading to more captured photons and larger photocurrent.Moreover,the fabrication of MSC is easy and the cost is low,making MSCs promising for large scale application.Typically,TiO₂ nanoparticles are used as the mesoscopic layer with good photovoltaic performance,however,the electron transport rate is not high,the light scattering ability is poor and the electron recombination is serious.Thus,the further development of TiO₂ morphology and electrode structure to obtain more efficient mesoscopic solar cells is desired.Specific work content is as follows:?1?Dye-sensitized solar cells?DSSC?are one of the typical mesoscopic solar cells.Commonly,TiO₂ nanoparticles?NP?are used in the photoanodes.However,a part of incident light directly transmits through the TiO₂ nanoparticle film without being harvested and utilized due to the small particle size of TiO₂.Additionally,the electron traps existing in the grain boundaries between nanosized particles lead to a low electron transfer rate and serious charge recombination loss in the film of TiO₂NPs.Here,a novel hierarchical TiO₂ submicrorods?HTRs?were synthesized with a higher surface area(103 m² g^-1).Composite photoanodes in dye-sensitized solar cells were prepared by integrating the prepared HTRs and P25 NPs,and a photovoltaic conversion efficiency of 8.09%was obtained when the HTR content was 20 wt%,which was obviously higher than that of the pristine P25 NPs-based photoanode?5.37%?.The incorporated hierarchical TiO₂ submicrorods in the hybrid photoanode film increased the specific surface area for effective adsorption of dye molecules,enhanced the light harvesting efficiency and accelerated the electron transport by the films.?2?Mesoscopic perovskite solar cells?MPSC?,as an important branch of dye-sensitized solar cells,have obtained photoelectric conversion efficiency more than 22%.However,the morphological control of TiO₂ mesoporous material and the optimization of electrode structure are still challenge in the field.Thus,we fabricate TiO₂/NiO nanosheet-based PSCs using mesoscopic TiO₂ nanosheets?NS?,p-type NiO nanosheets?NS?and carbon black/graphite as electron transport material?ETM?,inorganic hole transport material?HTM?and counter electrode?CE?,respectively.Furthermore,screen printing was used to fabricate PSCs with the TiO₂/ZrO₂/NiO/carbon?CH₃NH₃PbI₃?structure.The TiO₂/NiO nanosheet-based printable PSC showed a promising conversion efficiency of 7.50%,significantly higher than 6.40%of the device using the HTM of NiO nanoparticles?NP?.The electrochemical impedance analysis exhibited that NS structured PSC can decrease the electron recombination effectively and enhance the collection of the charge carriers,resulting in better photovoltaic performance.