UV Stability of Aluminum Oxide Fabricated with Tube‐Type Plasma‐Enhanced Atomic Layer Deposition

Ultraviolet (UV)‐induced degradation is a critical issue for modern photovoltaic (PV) technologies such as passivated emitter and rear cell (PERC), tunnel oxide‐passivated contact (TOPCon), and heterojunction (HJT) cell concepts. This study compares the stability against UV radiation of AlO _x /SiN _y stacks on mini‐modules with p‐type back junction solar cells. Our cells have a nondiffused textured front surface passivated with an AlO _x /SiN _y layer stack and feature passivating polysilicon on oxide rear contacts. We compare plasma‐enhanced chemical vapor deposition (PECVD) and plasma‐enhanced atomic layer deposition (PEALD) processes for the deposition of AlO _x layers using the same tube‐type deposition system. After a UV dose of 146 kWh/m ² using broadband UV lamps, modules with PECVD‐AlO _x exhibit an efficiency loss of up to 27% while those with PEALD‐AlO _x show minimal degradation of 2.5%. This comparison proves that the superior UV stability is achieved with the tube‐type PEALD technique. Our findings thus show how UV stability can be improved without extra equipment dedicated solely to depositing ALD‐AlO _x and without UV absorbing or down converting encapsulants.