Preparation Of Copper,Zinc,Tin And Sulfur ?Cu₂ZnSnS₄? Seed Layer And Its Effect On The Growth And Properties Of Cu₂S Counter Electrode

Quantum dot-sensitized solar cells?QDSSCs?have attracted more and more attention because of the light-absorbing materials,which have adjustable size,high extinction coefficient and so on.As one of the components of the QDSSCs,the counter electrode has an important impact on the performance of the cell.In the studies of counter electrode materials,copper sulfur compounds were the most,and the performance of Cu₂S prepared by etching copper was the best.However,the copper would suffer continuous corrosion in the electrolyte and finally result in disintegration.Therefore,in the past decades,many researchers began to improve the preparation methods of Cu₂S,and most people chose the fluorine-doped tin dioxide?FTO?as the substrate for the growth of Cu₂S,but neglected the lattice mismatch problem between FTO and Cu₂S.Especially for the methods like chemical bath deposition?CBD?and successive ionic layer adsorption and reaction?SILAR?,they all needed spontaneous nucleation growth,the crystal lattice structure of FTO would have a direct impact on the growth of Cu₂S and then affect its catalytic activity and the device performance.In order to solve this problem,we introduced CZTS between FTO and Cu₂S as the seed layer for the growth of Cu₂S,because it had more similar and more matched lattice structure with Cu₂S.Compared with the traditional substrate FTO,we thought that the CZTS would be more suitable for the growth of Cu₂S,and would produce more catalytic sites,which was beneficial to improve to the catalytic activity of Cu₂S counter electrode.The details were as follows:Firstly,the CZTS seed layer was prepared on FTO by simple solution method.To obtain optimal CZTS seed layer,we changed the solvent to adjust the formulation of CZTS precursor solution,and then got the CZTS seed layers with different structures.Then we used the method of CBD to grow Cu₂S on the surface of seed layers and tested their catalytic activity by the electrochemical impedance?EIS?,and then got the optimum morphology by analyzing the EIS results.We further optimized its thickness on the basic of morphology regulation by changing the spin-coating speed and numbers.To further study the influence of CZTS seed layer on the growth and properties of Cu₂S,we used the method of CBD to grow Cu₂S on FTO and FTO/CZTS and then studied the role of CZTS seed layer by a series of measurements.The results of scanning electron microscopy?SEM?showed that after introducing the CZTS,the Cu₂S particles obviously grew more,which was consistent with the results of the Raman test,this suggested that the CZTS was more suitable for the growth of Cu₂S compared with FTO.The test of catalytic activity further showed that the charge transfer resistance of FTO/CZTS/Cu₂S was smaller,and its catalytic activity was significantly improved.Finally,the device performance results showed that after introducing the CZTS seed layer,the filling factor was improved,and the device performance was enhanced.In summary,compared with traditional substrate FTO,the introduction of the CZTS seed layer could promote the growth of Cu₂S,improve the catalytic activity of the counter electrode and improve the filling factor,enhance the performance of the cell,meanwhile,it also provided a new idea for improving the performance of counter electrode in the future.