Research Of QDSC Based On TiO₂ Photoanode Modified With MWCNTs And G-C₃N₄

Quantum dot sensitized solar cell（QDSC）is considered as the most potential third generation solar cell because of high theoretical efficiency,easy processing and cheap raw materials.Inorganic quantum dot（QD）as a new type of light harvester possess many appealing advantages,such as high extinction coefficient,available bandgap adjustment and multi-excition effect.In this work,one-dimensional and two-dimensional materials were introduced into TiO₂photoanode of QDSC to optimize the electron transport and light absorption performance.Photoanode is the core component of QDSC and nano-sized TiO₂ is the most commonly used photoanode material.However,there will produce many tiny cracks in the porous photoanode film due to the different degrees contraction of TiO₂particles during sintering process,which seriously affects the solar cell performance.In this paper,multi-walled carbon nanotubes（MWCNTs）with the advantages of large specific surface,excellent electrical conductivity and unique tuber structure were used to modify the microcracks in photoanode films.Combined microstructure characterization,electrochemical impedance（EIS）and current density-voltage（J-V）curves to analyze various samples systematically.The results show that compared with bare TiO₂ photoanode QDSC,the power conversion efficiency（PCE）of QDSC based on MWCNTs/TiO₂ composite photoanode is 3.05%with an increase of 73.3%.Moreover,the photoanode thickness with MWCNTs/TiO₂ composite film was further optimized and the PCE of the QDSC reached the highest of 3.40%when the thickness was 11.6μm.The available PCE of QDSC is far below their theoretical thermodynamic efficiency,which can be ascribed mainly to the light absorption range of QD sensitizers and low electron injection efficiency.With urea as the nitrogen source,g-C₃N₄/TiO₂ composite powder was prepared by one-step annealed the mixture of urea and TiO₂ precursor which has an uniform microstructure.The PCE of QDSC is3.31%with an increase of 72.4%.G-C₃N₄ powder was prepared by using the melamine as the nitrogen source and g-C₃N₄ with different mass fractions was introduced into the TiO₂ photoanode.Due to poor mechanical mixing,g-C₃N₄ is easy to be stacked into blocks,so as to make the microstructure disordered.And the PCE of QDSC is 2.79%.