Interface Modification Of Titanium Oxides With Amino Acids For Perovskite Solar Cells

Perovskite solar cells as a new generation of solar cells, have become a hot research field in recent years. Its efficiency is up to 20%. At present, there is less research about interface modification in perovskite solar cell. In this work, we modified the cathode by amino acid to match the work function of cathode interface to the LUMO energy level of the active layer for the improvement of the power conversion efficiency. The main contents in this work are as follows:We modified ITO and TiO₂ surface by amino acids to investigate the change of their characteristics. The roughness of ITO and TiO₂ surface is not changed after the modification. Investigating the interfacial properties of amino acid/ITO and amino acid/TiO₂ by XPS, we proved that amino acid can adsorb on the surface of ITO or TiO₂ by hydrothermal reaction. Investigating the effect of interfacial modification on the function of ITO and TiO₂ with various amino acids in different solvents, we notes that the lysine methanol solution is the best, the function of ITO and TiO₂ declined 1.1 e V and 1.2 e V respectively.For devices based on PAN:CH₃NH₃PbI₃ system, we researched the change of the device performance by changing the growing conditions of amino acid. We received the optimum method of interface modification by comparing different process program. The substrate coated with TiO₂ reacted with lysine methanol solution whose concentration is 3 mg/ml. The reaction temperature is about 90℃ and the reaction time is 120 min. The performance of device is best by this method. The open-circuit voltage, short-circuit current, filling factor and conversion efficiency is 1.00 V, 21.53 m A/cm2, 0.54 and 11.61% respectively. However, the conversion efficiency of the device without interface modification can reach 12.51% as well as various performance parameters are superior to the device after interface modification. The main reason is that the compatibility between amino acid and PAN is much stronger, which produces to stratification. In addition, we researched the device with flexible structure and fabricated device wich conversion efficiency is 0.85%.For devices based on PbCl₂:CH₃NH₃I system, we also compared the effect of various precess program. We obtained the optimum technological scheme by comparison. The substrate coated with TiO₂ reacted with lysine methanol solution whose concentration is 3 mg/ml. The reaction temperature is about 90℃ and the reaction time is 120 min. The performance of device is the best by this method. The open-circuit voltage, short-circuit current, filing factor and conversion efficiency is 0.83 V, 19.51 m A/cm2, 0.53 and 8.64% respectively. Compared to the device without interfacial modification, the performance is improved.