Researchers at ISC Konstanz found that ALD-based aluminum oxide (AlOx) passivation layers provide better UV stability for TOPCon solar cells than PECVD-deposited layers, with thicker AlOx films and a thermally grown SiOx interlayer further improving resistance to UV-induced degradation. Testing laboratory and commercial TOPCon cells showed 2–3% average efficiency losses after high UV exposure, while process variations and layer non-uniformities were identified as key factors influencing long-term UV susceptibility.