Coupled experimental and theoretical investigation of the process parameters controlling the perovskite structure formation: towards thick defect-free layers

• Applicants: Dr.-Ing. Tian Du, Ph.D.; Professor Dr. Jens Harting
• Subject Area: Synthesis and Properties of Functional Materials ; Computer-Aided Design of Materials and Simulation of Materials Behaviour from Atomic to Microscopic Scale
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 506698391

Hybrid organic-inorganic perovskite materials have rapidly emerged as a highly promising alternative to silicon solar cells. However, the fundamental properties of the film formation mechanisms during solution-processing of the photoactive layers still remain poorly understood, which hinders the development of thick, vertically monolithic perovskite films with superior semiconducting quality. In this project, the main goal is to develop a precise model predicting film formation of solution-processed perovskite films, gain control over the fundamental governing mechanisms, and subsequently improve the film morphology.We propose a coupled approach where experimental measurements and simulation results complement each other. We will develop and use an in-situ measurement chamber to monitor the film formation under controlled conditions and in parallel we will perform phase field simulations of the nucleation and growth of perovskite crystals upon drying and post-processing. This will give insight into the morphology formation process, as well as into structural features of the dried film such as surface coverage, roughness, crystal sizes and stacking. We aim at establishing mechanistic rules regarding the impact of process parameters such as solvent choice, quenching temperature, rate and method, and post-drying steps on the final film quality. We will also investigate how nucleation agents introduced in the solution or at the substrate can be used to monitor nucleation and improve the film quality. The established physics-based design rules for ink formulation and process parameters will be used to demonstrate experimentally defect-free polycrystalline film structures, even for thick layers and for different precursor solution formulations. Selected perovskite films will be completed to solar cells in order to validate the impact of the morphology improvement on the photovoltaic performance.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2196: Perovskite semiconductors: From fundamental properties to devices
• Co-Investigator: Professor Dr. Christoph J. Brabec