Role of organic cation orientation in formamidine based perovskite materials

Siyu Liu,Zhongtao Duan,Fengxian Xie,Jing Wang,Zhe Hu,Hao Zhang,Wanlu Zhang,Ruiqian Guo

doi:10.1038/s41598-021-99621-1

Abstract

The rotation of organic cations is considered to be an important reason for the dynamic changes in stability and photoelectric properties of organic perovskites. However, the specific effect of organic cations rotation on formamidine based perovskite is still unknown. In our work, first-principles calculations based on density functional theory are used to examine the effect of the rotation of formamidine cations in FAPbI3 and FA0.875Cs0.125PbI3. We have comprehensively calculated the structure, electronic and optical properties of them. We found a coupling effect between formamidine cations rotation and cesium atom. This coupling effect changes the inclination angle of octahedron to regulate electron distribution, band gaps, and optical absorption. Hence, changing the cation orientation and substitution atom is a feasible way to dynamically adjust the energy band, dielectric constant and absorption edge of perovskite. Preparing perovskite with tunable properties is just around the corner through this way.

Highlights

We found that the coupling effect of organic cations and cesium atom affected many properties of this mixing system, such as lattice constant, band structures, charge distribution, dielectric constant, optical absorption properties, and even the performance of solar cell device (Fig. 1)
All the calculations have converged on the energy convergence standard 1 0–5 eV and the force convergence standard 0.01 eV·Å−1 per atom by using generalized gradient approximation (GGA)-PBE exchange correlation functional[21] with van der Waals force correlation[22] without considering the spin–orbit coupling (SOC)
We calculated cohesive energy and abinitio molecular dynamics (AIMD) in 400 K to confirm the dynamical stability of these hybrid p erovskites[27,28]

Summary

Introduction

We found that the coupling effect of organic cations and cesium atom affected many properties of this mixing system, such as lattice constant, band structures, charge distribution, dielectric constant, optical absorption properties, and even the performance of solar cell device (Fig. 1). According to the non-doped FAPbI3 perovskite, the interaction of formamidine with PbI6 octahedron leads to a considerable disorder, which alters its volume (cell volume is changed as well) (refer to Table 1; Fig. 2).

Results

Conclusion