Theoretical Study Of Carrier Mobility In Perovskite Solar Cells

With the rapid of the technology growth, the quality of people's living life is getting better, however, environmental pollution and energy crisis are still two main problems we face in society. As the traditional energy consumption and the growing scarcity, looking for a new kind of clean energy is imminent. In numerous of new and clean energies, the solar energy, with its universality, harmless, abundant and longevity, has become the preferred material. In the third generation solar cells, the perovskite solar cells stand out with its efficient performance, only in a short span of five years from the initial efficiency of 3.8% rapidly increased to 22.1%, and endowed with "one of the ten major scientific breakthrough" by Science magazine in 2013. The high photoelectric conversion efficiency of the battery is mainly because it is inside the light absorption layer (perovskite) semiconductor material has a longer exciton diffusion length, and the carrier mobility is one of the decisive factors in semiconductor materials diffusion length.In this article, we based on the theory of Marcus-Hush and Density Functional Theory (DFT), using Gaussian 09 software and Amsterdam Density Function (ADF2012) software to calculate the charge transport microscopic physical quantities in perovskite crystal (CH3NH3PbX3, X=Cl, Br, I), it includes molecular vibration (reorganization energies,?) and molecular electronic coupling integral (the charge transfer integral, V), and according to the above parameters for the carrier mobility of perovskite crystal and its anisotropy has carried on the theoretical research.The main work of this paper:(1) one-dimensional infinite was deduced under the deep well of Frank-Condon formula; (2) construct different halogen perovskite structure models, structure optimization with different functional and basis set to select the appropriate one; (3) adopt Gaussian 09 software to optimize the structure of the selected model to calculate vertical/adiabatic ionization potentials (IP), vertical and adiabatic affinity (EA) energy, HEP energy, EEP energy and reorganization energy; (4) adopt ADF2012 software to calculate electronic coupling integral of the selected model; (5) calculate the different perovskite crystal along three major axis direction of carrier mobility; (6) calculate the anisotropy of carrier mobility in five low index crystal face of perovskite (CH3NH3PbI3) and analyzes the differences.By comparison of the results we found that:perovskite materials are mainly based on the electron transport, that is to say the material is an n-type semiconductor, halogen will have certain influence on the transmission performance in perovskite materials, the largest carrier mobility is bromide, the second carrier mobility is iodine, the smallest carrier mobility is chlorine. When the perovskite is CH3NH3PbI3, the anisotropy of the carrier mobility on different crystal faces is different, and in (010), (101), (110) crystal plane on the transport of electrons and holes in the same direction. The best transport direction of electron and hole arised in [001], [010], [100] crystal orientation. which provided theoretical support for designing high performance electronic devices.