Study On Properties Of Organic-Inorganic Hybrid Perovskite By SKPM

Since 2009, organic-inorganic hybrid perovskite CH₃NH₃PbX3?X represents a halogen element? solar cells have attracted much attention in PV industry and its power conversion efficiency has surpassed 20% from initial 3.8%. Meanwhile, the perovskite can be synthesized by simple solution method and the required processing temperature is less than 150?, thus it is an economical and efficient photovoltaic material. Despite its rapid development, the fundamental physical mechanisms are still unclear, requiring more technical means to clarify the optoelectronic properties of the material itself.In this thesis, we synthesized a series of common perovskite materials by simple solution method, including CH₃NH₃PbI₃, CH₃NH₃PbI_3-xClx, CH₃NH₃Pb?I1-xBrx?3 and CH₃NH₃Pb?Br1-xClx?3. By using Scanning Kelvin Probe Microscope?SKPM?, we studied the morphology and surface potential of these perovskites. The details are as follows:?1? Rod structure and particle structure perovskites are formed by solution method. SKPM results show that for rod-CH₃NH₃PbI₃, its surface potential is not affected by the synthesis conditions and rod size. The electrical properties of perovskite material are very stable and are not sensitive to impurities or defects. Further, SKPM results show that at the perovskite/FTO interface, the perovskite energy band bends downwardly about 45 meV.?2? We then studied in detail the particle-CH₃NH₃PbI₃. First, from a detail analysis of the topography, phase and potential images of the perovskite particles, we conclude that Pb I2 may not be completely converted to perovskite during reactions. It is also evidenced by its absorption spectra. Then, we studied the surface potential of perovskite particle on substrates of different conductivity type and found that perovskite conductivity depends on the conductivity type of substrates. In addition, we studied photo-induced charge separation effect of perovskite particle and the morphology changes of particle-CH₃NH₃PbI₃ under external electric field.?3? We studied the surface potential of CH₃NH₃PbI_3-xClx perovskite made from different concentrated precursor solutions. The surface potential changes are likely caused by chlorine content in CH₃NH₃PbI_3-xClx samples.?4? By using UV-vis, PL, SKPM, we studied the optoelectronic properties of hybrid perovskite CH₃NH₃Pb?I1-xBrx?3 and CH₃NH₃Pb?Br1-xClx?3. The surface potential is related to work function of the material. The local potential difference observed in some samples is also explained.