Study shines light on major degradation pathways in wide-bandgap perovskite cells

A study published in Materials Futures reveals critical insights into the degradation mechanism of scalable, wideband gap perovskite solar cells, a key component for the next generation tandem solar technologies.

Researchers from imec, Hasselt University, and Ghent University in Belgium have identified how thermal stress, both in the dark and under illumination, critically affects the stability of these solar devices. Their findings reveal that in dark conditions, failure is mainly driven by the charge transport layers, whereas under light exposure, the failure is associated with degradation of the absorber material itself.

By subjecting the devices to accelerated stress tests that mirror industry standards, the team has mapped out the key failure pathways, offering a clearer understanding of how to enhance long-term stability.

This research represents a major advance in the push toward commercially viable, high-efficiency perovskite solar technologies—a crucial step for the future of sustainable energy generation.

Wide bandgap (WBG) hybrid-organic lead halide perovskites have gained significant attention, mainly due to their promising optoelectronic properties making them suitable candidates to be integrated as top cell absorbers in very-high-efficiency tandem solar cells.

Despite this, these wide bandgap perovskites typically face poor stability under light and at elevated temperatures. This is because of the phase segregation mechanism, in which bromide and iodide species that constitute part of the perovskite crystal separate in distinct phases, therefore hindering the layer stability.

While various techniques have been explored to overcome this phenomenon, there are only very few reports showing the success of such techniques on full devices under different stressing conditions. Moreover, most of the devices reported in the literature were manufactured using lab-scale, non-scalable techniques such as spin-coating, which limit their relevance for industrial application.

In the Materials Futures paper, a research team conducted a thorough side-by-side analysis of the degradation of WBG perovskite cells vs. more stable narrower bandgap devices.

A standard methodology, derived from the International Summit on Organic Photovoltaic Stability (ISOS) protocols, was used for testing the stability, namely ISOS-D2 and ISOS-L2. To understand the cause of degradation in each of these cases, a comprehensive electrical characterization toolbox was used.

From this analysis, it emerged that different degradation modes are observed in different stressing conditions, emphasizing that “perovskite stability” may not be an absolute concept. Degradation under ISOS-D2 (thermal stress in the dark) originates mainly from an issue at the perovskite/ETL layer.

Degradation under ISOS-L2 (thermal stress under light), on the contrary, was caused by a dramatic deterioration of the perovskite absorber layer. This important finding emphasizes the role of heat on the phase segregation process and on the degradation of WBG perovskites under operational conditions, which was overlooked in many previous studies.

In the future, several steps are yet to be undertaken before this material becomes suitable for industrial-scale deployment. First, a more detailed understanding of the nanoscale-level degradation in different stressing conditions is required. This goes in parallel with efforts to improve the stability of the wide-bandgap perovskite, not only at material but also at cell and module level.

Secondly, these devices should be tested in a wider range of stressing conditions, potentially leading to the discovery of new degradation modes.

Outdoor field deployment is central among these tests, as it mimics the real-life operation of devices and should highlight which accelerated tests are the most representative to reproduce these conditions.

Finally, when moving toward the commercialization of this technology, clear industrial standards for stability should be set and coupled with adapted and standardized accelerated stress tests.

This work constitutes a key milestone in understanding the stability issues in wide-bandgap perovskite solar cells, to eventually enable its commercialization and the emergence of the next-generation, ultra-efficient, solar cell technology.

Provided by
Songshan Lake Materials Laboratory