Configuration and Electronic Properties of the Interface between Lead Iodide Hybrid Perovskite and Self-assembled Monolayers in Solar Cells

Hybrid perovskite photovoltaic materials are currently the most promising functional materials for solar cell applications with efficiency reaching to those of more conventional materials such as silicon. Using self-assembled monolayers between photovoltaic materials and electrodes is a method for improving the stability and functionality. Recent experiments have shown that using 4-mercaptobenzoic acid and pentafluorobenzenethiol monolayers bridging lead iodide hybrid perovskite photovoltaic materials and electrodes result in improved stability and efficiency. The details of monolayer assembly, molecular adsorption configuration, and resulting modification of electronic properties are important characteristics related to solar cell performance. These characteristics can be obtained through accurate computer stimulations. Here we use ab initio computer stimulations to model adsorption characteristics of this monolayers. First we determine the structure of bulk and reconstructed surfaces of hybrid perovskite. Next we use several initial adsorption configurations to optimize the molecules attachments to reconstructed surfaces and find the most stable geometries. These are than used to determine electronic properties including charge accumulation, Electrostatic potential, and density of states at different interfaces. The effects of different monolayers and different hybrid perovskite surfaces on interfacial electronic properties are compared and discussed.