High Efficiency Solar Cells Based On Cl-doped Organometal Halide Perovskite

Perovskite solar cells based on organmetal halide light absorbers have been considered a promising photovoltaic technology.Compared to other types of solar cells, perovskite solar cells developing very rapidly.Perovskite materials have excellent characteristics and photoelectric properties. Firstly, perovskite materials have nearly perfect crystallinity, which is the common features of crystalline silicon solar cells and GaAs(gallium arsenide) solar cells.However, the process of manufacturing perfect inorganic solar material generally requires very high temperatures, expensive vacuum equipments and complicated growth process, the high crystallinity perovskite materials can be synthesized at a low temperature and a simple chemical method. Meanwhile, perovskite materials have excellent light absorption properties and suitable band gap width(about 1.5 eV),and the light absorbing capacity of perovskite materials are more than 10 times higher than organic dyes, for 400 nm thick film can absorb all ultraviolet Near Infrared Spectroscopy photons. In addition, perovskite materials have long-range carriers diffusion performance, and the effective carrier diffusion length of chlorine doped lead iodate methylamine exceeds 1 μm, which is 100 times than the organic solar cell materials. Furthermore, the basic energy loss of perovskite solar cells during photovoltaic conversion process is very low, which is about 0.4 eV, and the energy loss of commercial silicon solar cells is about 0.4 eV, so this feature is far superior to conventional dye-sensitized cells (0.8 eV).This study presents the idea of preparing planar heteroj unction perovskite solar cells, using PbI2(lead chloride) and CH3NH3l(methylamine) as the source material to produce perovskite materials CH3NH3PbIxCb-x, which is used as light absorbing layer of the solar cell, and using FTO as a transparent conductive electrode for electron collecting, and a spin-coating method was used for preparing an electron transport layer (dense layer of titanium dioxide),the light absorbing layer (perovskite layer) and the hole transport layer, hole collection layer was prepared by thermal evaporation technique.Our design abandon the mesoporous TiO2 layer in traditional dye sensitized solar cells, simplifying the device structure and preparation process,and geting the planar structure heterojunction thin film solar cells eventually.The crystal structures of the perovskite films were measured by X-ray diffraction. The absorption spectra of the mesoporous and planar perovskite films were characterized by an UV/vis-NIR spectrophotometer.The morphology of solar cell materials were observed using a field-emission SEM.The performance of solar cells were measured using a solar simulator with a source meter at 100 mA/cm2 AM1.5G illumination, the average PCE of 5 layer solar cell reach 9.05%, the optimal solar cells reaches a PCE of 10.88%, a open-circuit voltage of 0.88 V, a short circuit current 23.71 mA/cm2, a fill factor of 52.7%.