In recent years, the organic-inorganic hybrid perovskite material has been a wave of research in photovoltaic energy field due to its tunable bandgap, high absorption coefficient, bipolar carrier transmission property, long carrier diffusion length and low defect density, and other excellent photoelectric characteristics. With only nine years of technological development, the device performance of polycrystalline perovskite thin-film solar cells has been comparable to that of a 60-year-old crystalline silicon battery, which has grown much faster than any other solar cell technology in history. From 2009 to date, researchers around the world have developed one-step spin coating, two-step spin-coating, steam-assisted, scraping coating, and many other thin film preparation and solvent engineering, component engineering, interface engineering, and other device optimization criteria, On the macroscopic scale of improving the quality of perovskite polycrystalline film and optimizing the structure of the device, the solar cell is moving towards high conversion efficiency. However, at present, there is still less research on the depth of perovskite materials and devices in the microscopic and mesoscopic scales, the lack of rational knowledge of the structure-effect relationship between the material microstructure, the carrier transport characteristics and the device performance directly hinders the further improvement of the device efficiency, and based on this,
Exploring the potential regularity between material microstructure and photovoltaic performance will be a key step to improve the performance of perovskite solar cells. The Zhou Huanping team of Peking University Institute of Technology used the synchrotron radiation x-ray swept incidence wide-angle scattering technique (GIWAXS) from the center of the National Science installation, and systematically studied the optimal orientation of the crystal surface of the mixed cation-based perovskite polycrystalline thin film with the highest efficiency. The direction of the substrate stacking arrangement is controlled by the fine doping of the multi-cation cascade, and the better device performance is obtained. Further, the team from the carrier transport characteristics of the different preference-oriented relationship between the multi-crystalline thin film and device performance of the inherent law, found that parallel to the substrate (001) The strong preferred orientation of the crystal face family will promote the high-speed carrier in the film transfer, improve the carrier in the Perovskite and Transport layer interface between the transmission rate and collection efficiency , the specific crystal surface stacking method and the preferred orientation relationship provide more efficient carrier transport behavior, resulting in a significant improvement in battery device performance. The results show that the cascade doping of multiple cations is effective in controlling the optimal orientation of polycrystalline thin films, which brings about a rational understanding of the structure-effect relationship between materials microstructure and photovoltaic performance, and provides a new design idea for the current cell breaking efficiency bottleneck. The results were published in the famous journal polycrystalline Films ' manipulation of facet orientation in hybrid perovskite cation cascade by Nature Comm ' Unications "Nature Communications 9, 2793 (2018). Doi:10.1038/s41467-018-05076-w ", Peking University and Shanghai Institute of Applied Physics jointly cultivate doctoral Zheng hero and Beijing University of Science and Technology PhD Zhu Cheng Dehui as the joint first author of the paper.
Peking University is the first unit. Orientation Evolution Analysis of cationic multi-cascade doping of alkali metals: (a) FAMA, Fama-cs, FAMA-CSRB, FAMA-CSRBK Cascade doped polycrystalline film giwaxs pattern; (b) FAMA, Fama-cs, FAMA-CSRB,
FAMA-CSRBK-doped polycrystalline thin Film (001) The azimuth integral strength of the crystal surface; (c) schematic diagram of the orientation evolution of the crystalline surface of a cascaded doped polycrystalline thin film This research system investigates the influence of the multi-cascade doping of alkali metal cation cs+, rb+, K + on the crystal stacking orientation, realizes controllable orientation regulation through fine doping, and reveals that the preferred orientation of the microstructure level greatly influences the photoelectric properties of perovskite material, and confirms the parallel to the substrate (001) The strong preference orientation of the crystal faces will promote the high-speed migration of carriers in the film, improve the transmission rate and collection efficiency of the carriers at the interface between perovskite and transport layer, establish a clear and definite structure-effect relationship between the perovskite polycrystalline microstructure, device performance and carrier transport characteristics,
It provides a new design idea for the current battery breakthrough efficiency bottleneck. The study was carried out in collaboration with Professor Mr Chan of Beijing Institute of Technology, Gao Xingyu researcher at Shanghai Institute of Applied Physics, Hu Jessie researcher at the Institute of Chemistry, Chinese Academy of Sciences, and Professor Hong Jiawang of Astronautics College of Beijing Polytechnic University.
