Structure optimization and optoelectronical property calculation for organic lead iodine perovskite solar cells

Abstract

Methylamine lead iodide (CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> MAPbI<sub>3</sub>) and formamidine lead iodide (CH(NH<sub>2</sub>)<sub>2</sub>PbI<sub>3</sub> FAPbI<sub>3</sub>) are the most commonly used organic lead iodine perovskite materials for solar cell research. For the perovskite solar cell with a layered structure, the optical properties and thickness of each layer affect the photoelectric conversion efficiency of the cell. In this paper, the optical admittance method and rigorous coupled wave analysis method are used to calculate the absorptivities and transmittances of metal oxide transparent conductive films for tin-doped indium oxide (In<sub>2</sub>O<sub>3</sub>:Sn), fluorine-doped tin oxide (SnO<sub>2</sub>:F), TiO<sub>2</sub>, MAPbI<sub>3</sub> and FAPbI<sub>3</sub>. The influence of each layer thickness and device structure on the short-circuit current density of the cell are analyzed. It is shown that for the FTO(ITO)/TiO<sub>2</sub>/MAPbI<sub>3</sub> structure, when the thickness of the FTO film is 50–450 nm and the thickness of the ITO film is 10–150 nm, the average transmittance for the 360–800 nm wavelength light is 85%. For the FTO(ITO)/TiO<sub>2</sub>/FAPbI<sub>3</sub> structure, when the thickness of the FTO film and ITO film are 50–250 nm and 10–150 nm, respectively, the average values of the transmittance for the 360-840 nm wavelength light are 81.6% and 78%, respectively. Under the optimal thickness of FTO and TiO<sub>2</sub>, and the thickness of MAPbI<sub>3</sub> and FAPbI<sub>3</sub> are 300–1000 nm, the corresponding short-circuit current densities are in a range of 21.9–23.7 and 23.0–24.4 mA·cm<sup>–2</sup>, respectively. The band gap of MAPbI<sub>3</sub> and FAPbI<sub>3</sub> are 1.56 and 1.48 eV, for which the corresponding absorption cut-off wavelengths are 796 and 840 nm, respectively, indicating that FAPbI<sub>3</sub> has a wider absorption spectrum than MAPbI<sub>3</sub>. In order to maximize the Jsc value of the organic lead iodine perovskite solar cell, the thickness range of each layer for MAPbI<sub>3</sub> perovskite solar cell (FTO thickness is (80 ± 50) nm, ITO thickness is less than 120 nm, MAPbI<sub>3</sub> thicknessis 300–600 nm) and for FAPbI<sub>3</sub> perovskite solar cell (FTO thickness is (120 ± 50) nm, ITO thickness is less than 180 nm, FAPbI<sub>3</sub> thickness is 300–600 nm) are given. The research results of this article have guiding significance in designing and preparing the perovskite solar cells with high conversion efficiency.