ORIGIN OF DEGRADATION IN THE LONG-TERM PEROVSKITE MODULE OUTDOOR PERFORMANCE IN DIFFERENT OUTDOOR REGIONS

In the domain of perovskite formulations, module architectures, and layer stacks offering possibilities for processing highly efficient devices, comparing performance stability data across literature presents a considerable challenge. While perovskite outdoor stability data has been investigated by some research groups [1][2] [3] most samples, even for many perovskite compositions and architectures, have been relatively short-lived. Specific investigations include extensive datasets, yet measurements are confined to cells[4],[5],[6]leading to conclusions influenced by the small device areas and lack of interconnections. Despite the presentation of high-performing devices showcasing operational stability, the hurdles in achieving fabrication on a larger scale persist. Various consortia and partnerships, involving universities, companies, research institutes, and national laboratories, have been established to address these issues. One such consortium is US-MAP (Manufacturing of Advanced Perovskites), which collects and uniformly reports outdoor performance data for perovskite modules.

Our methodology comprises a reproducible and scalable process, an operationally stable perovskite formulation, and a photo and thermally stable layer stack (layer stack: ITO/NiOx/ FA_0.80Cs_0.20Pb(I_0.94Br_0.06)₃ /ETL/ITO). The robustness of this process is demonstrated by its run-to-run reproducibility, establishing a foundation for an equitable comparison of outdoor performance among samples. We present the real-time performance of our perovskite modules over 4 years and discuss the strategies employed to achieve more extended stability as we scaled up our modules to 800 cm2 [7].

Our innovative approach integrates a feedback loop based on in-lab characterization, outdoor performance results, and degradation analysis to enhance our understanding and enable adjustments for prolonged lifetimes. In the conference we will elaborate on our approach to the performance tests that have led to process modifications, giving rise to new generations of modules characterized by improved performance, stability, and area coverage.

We investigate the data for the correlation between outdoor performance and irradiance levels, alongside temperature variations. Figure 1 displays the mini-module PCE evolution up to the summer of 2024 alongside the temperature variations of the modules. Preliminary analysis suggests a consistent burn-in period for all samples, within the initial 3 months of outdoor deployment. This results in a performance decline of approximately 30% from the initial levels, followed by a performance stabilization over extended durations. From this dataset extending from 6 months in some locations to +4 years in others, we expect to discern dependences on irradiance levels, seasons, climates, and temperatures. Insights from the outdoor deployment of modules in Cyprus highlighted potential reasons for module failure, such as thermomechanical issues or the formation of ionic barriers. Through further investigation and deeper characterization, we aim to determine whether permanent degradation arises primarily from one of these stressors or a combination of both.

Figure 1: Upper plot: PCE evolution over time for samples considered in the study. Lower plot: Module temperature variations for different locations considered in the study.

Using the insights gathered from outdoor performance data, our objective is to refine our perovskite formulation, layer stack, and module design. Looking ahead to future developments, we are focusing on Gen 3 modules, to enhance the performance of our large-area modules while maintaining their exceptional stability.