Effect of doping on the phase stability and photophysical properties of CsPbI2Br perovskite thin films.

Lahoucine Atourki,Mohammed Regragui,Miguel Mollar,Mohammed Abd-Lefdil,Khalid Bouabid,Ahmed Ihlal,Mari Bernabé,Mohammed Makha

doi:10.1039/d0ra08912e

Abstract

In this study, we demonstrate that the crystallization process of CsPbI2Br films can be modulated when small amounts of additives are added to the precursor solution, leading to the formation of the bright brownish α-phase perovskite films with high orientation along the [100] crystallographic direction. Doped CsPbI2Br films exhibit improved crystallinity, with high coverage, large grain size and pinhole-free surface morphology, suitable for making high performance optoelectronic devices. We also explored the role of Cl in the photophysical properties of CsPbI2Br perovskite films using the temperature dependent photoluminescence technique. We found that the Cl ions enhance the photoluminescence emission by reducing the density of trap states, and also decrease the exciton binding energy from (22 ± 3) meV to (11 ± 2) meV. We believe this work contributes to understanding the effect of doping on the crystallization process with an in-depth insight into the photophysical properties of the cesium-based perovskite materials.

Highlights

Inorganic cesium-based perovskite materials have gained much research interest for numerous applications due to their excellent thermal stability
We have shown that small amounts of dopants provide an effective means of improving the morphology and stability of all inorganic CsPbI2Br perovskite materials relevant to photovoltaics applications
We have found that the crystallization process of CsPbI2Br lms can be modulated when ClÀ, Bi3+ or Rb+ ions were added to the precursor solution, leading to the formation of the bright brownish a-phase with high orientation along the [100] crystallographic direction

Summary

Introduction

Inorganic cesium-based perovskite materials have gained much research interest for numerous applications due to their excellent thermal stability. The CsPbI3 perovskite could be a potential alternative for APbX3 (A 1⁄4 MA, FA, GA, X 1⁄4 I, Br),[1].the cubic phase of CsPbI3 is only formed at higher temperatures and degrades rapidly in ambient air into a yellow non-perovskite phase.[2,3] In addition, the low intrinsic thermal stability and the low formation energy of Cs based perovskite materials generate a high density of defects on the surface and grain boundaries of polycrystalline lms, limiting their application. The addition of certain amount of CsCl2 in a solution of CsPbI2Br precursor stabilizes the black phase at room temperature under ambient conditions

Results and discussion

Conclusion

Conflicts of interest