HAXPES studies of functional perovskite interfaces
Understanding the energetics, structure and chemistry of HaP interfaces is key for developing HaP as a functional material for solar cell and light emitting diode applications. We have developed a methodology to carry out operando HAXPES measurements on working lead halide perovskite solar cells interfaces through a design of thin interface and contact layers. This would allow us to elucidate the band alignment, interface reactions and voltage losses/gains across the interfaces of perovskite solar cells with different selective contacts comparing dark and illuminated samples.
Status: Ongoing
Date of proposal: 30/08/2023
Start date: 06/09/2022
End Date: 11/09/2022
Used Instruments: HZB_XPS/HAXPES
Experimental Technique: X-ray photoemission measurements at different photon energies. High-Resolution Hard X-Ray. Photoelectron Spectroscopy (HAXPES). Application of bias voltage across perovskite layers with simultaneous HAXPES measurements.
Experiment Description: The study aimed to perform x-ray photoemission measurements on halide perovskite samples with extremely thin contact layers under dark conditions and with illumination. The project focused on determining the band alignment changes from core level energy shifts of interfaces to quantify voltage loss at the hole-conductor and electron-conductor interfaces. The study also examined how voltage influences internal fields and band alignment as well as ion movement in perovskite.
Type Samples: Halide perovskite single crystals (MAPbI3, MAPbBr3, FAPbBr3, FAPbI3, Cs0.17FA0.83PbI3). Chalogenide perovskites (BaZrS3 sputtered thin films).
Sample Description: Perovskite samples with extremely thin contact layers, analyzed under different conditions.
Experiment Data Type: Core level shifts and energy shifts under various conditions. Valence band measurements.
Characterization Technics: Photoelectron spectroscopy. Depth profiling using different photon energies.
Characterization Data Type: N1s, C1s, Pb 5d, O 2s, I 4d, Cs 4d, Cu 3p core energy levels spectra. Valence band analysis.
Analyzed Data: Effects of bias voltage and illumination on perovskite samples. Changes in core levels and valence band under different experimental conditions.
Main Targets Project: Analyzing voltage loss and interface chemistry in halide perovskites. Investigating the effects of voltage and illumination on band alignment and ion movement.
Main Achievements Findings: Successful measurement of the effects of bias voltage and illumination on halide perovskite samples. Observation of shifts in core levels due to bias voltage and illumination, returning to original values after excitation sources were turned off. Ongoing analysis but successful demonstration of the method's effectiveness. Encountered some difficulties with sample holder and contact problems during measurements.