Improving Durability in the Next Generation of Photovoltaic Materials Through Discovery and Mitigation of Interface-Based Degradation Mechanisms

Project Overview

In this project, advanced simulations and X-ray diagnostics were used to understand the interfacial structure and degradation pathways that influence the stability and performance of next generation, thin-film, photovoltaic (PV) materials. PV systems based upon thin film, heterojunction, architectures exhibit many attractive features for renewable energy applications, including low production costs, tunable band structure, and power conversion efficiencies consistent with the best commercial solar cell devices; nonetheless, thin film PV systems frequently exhibit performance-limiting properties, including degradation under a range of external stimuli and/or undesirable interfacial behavior. The combined experimental-simulations approach adopted in this research was applied to thin film photoabsorber materials from two technologically-relevant groups: cadmium selenium tellurides (CST), and inorganic-organic metal halide perovskites. Fundamental new insight was derived regarding the effects on electronic and geometrical structure of the CST and perovskite materials resulting from (i) changing photo-absorber composition, (ii) common surface treatments known to enhance performance, (iii) formation of heterointerfaces consistent with those used in functional devices, and (iv) controlled and accelerated aging. Furthermore, first principles calculations revealed new understanding of the role of environmental conditions (pressure, composition of atmosphere) on the stability of a canonical perovskite photoabsorber, CsPbI3. The collective findings of this project have broad and valuable implications for the rational design of next generation PV systems with enhanced properties.

Mission Impact

The cutting-edge and unique combination of advanced simulations, state-of-the-art X-ray diagnostics, and device fabrication/aging applied in this project provided groundbreaking insight into the interfacial and degradation behavior of next generation photovoltaic materials, which directly supports the Lawrence Livermore National Laboratory (LLNL) core competency in Advanced Materials and Manufacturing, particularly by providing capabilities for the accelerated development of advanced energy materials. The research also aligns with the aims of the Energy and Climate Security Mission Focus Area. Significantly, the combined experiment-simulation approach adopted in the project has the potential for impacting other projects and programs across LLNL that require advanced materials characterization, with particular relevance to phenomena at buried interfaces. The project has also increased LLNL expertise in the characterization of solar cell materials and has resulted in effective and sustaining collaborations with energy storage and conversion experts at University of Toledo.

Publications, Presentations, and Patents

Kweon, K. E., et al. 2023. "Influence of External Conditions on the Black-to-Yellow Phase Transition of CsPbI3 Based on First-Principles Calculations: Pressure and Moisture." Chemistry of Materials, 35, 2321-2329, DOI: 10.1021/acs.chemmater.2c03065 (LLNL-JRNL-756599)

M. Shelby, et. al., "Characterization of Interfacial Structure and Electronic Properties in Cadmium Telluride Thin-Film Photovoltaic Devices with X-ray Absorption Spectroscopy" (Oral Presentation, ACS Fall 2022, Chicago, IL, August 21-25, 2022). (LLNL-PRES-826794)

K. E. Kweon, et. al., "Insights from first-principles calculations to improve structural stability of black-phase CsPbI3" (Oral Presentation, ACS Fall 2022, Chicago, IL, August 21-25, 2022). (LLNL-PRES-839089)