Research On The Preparation And Interface Of Carbon-based Perovskite Solar Cells

From 2009 to date, the photoelectric conversion efficienc y of perovskite solar cells increased from 3.8% to 21.1%, which has been able to compare favorably with that the single crystal silicon cells(25.6%). However, there are several problems that limited their large-scale production and application, such as the requirements of expensive organic semiconductor as a hole transport layer, a layer of precious metal(Au or Ag) as a back electrode with evaporation, and unstability light-absorbing layer of perovskite solar cells. The preparation of perovskite solar cells with the conventional method not only costs high cost, but also needs high-tech equipments. At present, reducing the cost of perovskite solar cells. and improving their stability are the technical problems needed to be solved urgently.The carbon materials have the advantages of rich species, good conductivity, low cost and easy to operate, in which hydrophobic carbon electrode material is an excellent substitute for metal electrode material. In this paper, the carbon electrode materials are used as the back electrode to prepare perovskite solar cells, and we explored two kinds of carbon electrode materials with diff erent structure and composition. This study was carried out from the following aspects:(1) We researched the preparation technology of perovskite photovoltaic cells using the porous carbon film as back electrode. Firstly, the FTO/c-Ti O2/m-Ti O2/m-Zr O2/m-C heterojunction thin film as substrate was prepared, and the perovskite precursor solution was then dropped on the top of m-C layer. We found that the wettability of the perovskite precursor solution on substrate directly affects the solution diffusion into the interior of the substrate, and also determines whether the solution can be spread to the m-Ti O2 layer for forming good m-Ti O2:CH3NH3Pb I3 P-N interpenetrating heterostructure.In order to improve the substrate wettability of the perovskite precursor solution adequately, some kinds of solvents were used to pretreat the substrate, and we found that DMF can reduce the surface tension of perovskite precursor solution on porous layer by J-V curve. In addition, except for changing the substrate wettability, the thickness of each layer of the substrate and the annealing temperature also have a great influence on the photoelectric conversion.(2) We researched the preparation technology of perovskite photovoltaic cells using self-support carbon film as back electrode. The cell structure was FTO/c-Ti O2/m-Ti O2/CH3NH3 Pb I3/f-C, and the perovskite light absorbing layer was prepared by fast crystallization method. We found that the time of dropped chlorobenzene on perovskite thin films was critical to the quality of film deposition. If adding early light absorbing film is radial, and ifadding late the precipitation of CH3NH3 Pb I3 crystal will be unaffected. In addition, the annealing temperature of perovkiteis layer is an important influencing factor, which affects the CH3NH3 Pb I3 crystallization and crystal particle size indicated by SEM and XRD measurement.The self-supported carbon film was prepared by carbon slurry film, in which the ones of low resistance, good conductivity and certain flexibility were used. Then we improved the interfacial contact between self-supported carbon film and the perovskite light-absorbing layer and decreased the interface resistance by optimizing the hot-pressing temperature and time.