(Invited) ALD Enabling High-Efficiency Solar Cells

Abstract

Atomic layer deposition (ALD) can synthesize materials with atomic-scale precision. The ability to tune the material composition, film thickness with excellent conformality, low-temperature processing, and in-situ real-time monitoring makes this technique very appealing for a wide range of applications. In this contribution, we will show that ALD is already widely used in the manufacturing of industrial silicon solar cells, where ALD aluminum oxide is used for the passivation of the rear of PERC (Passivated Emitter and Rear Contact) solar cells. ALD aluminum oxide layers can also be used to reduce the contact resistance and firing temperature for phosphorous diffused surfaces. We will show that ALD layers can also avoid potential induced degradation (PID, a possible failure mode for large photovoltaic systems) at the solar cell level. ALD capping layers can also be used to reduce light and elevated temperature induced degradation (LeTID), which is a recently identified failure mode for high-efficiency solar cells, by acting as a blocking layer for hydrogen. Finally, we will show that ALD layers are enabling world-record CZTS (copper-zinc-tin-sulphide) solar cells.