(Invited) Application of ALD-Grown Metal Oxide Layers for Energy Applications: Photovoltaic and Photoelectrochemical Water Splitting

Abstract

ALD is a versatile growth technique for depositing a thin conformal layer of various functional materials. In this presentation, I will discuss two applications of ALD in energy materials research—photovoltaics (PV) and photoelectrochemical (PEC) water splitting. In the PV part, I will present how ALD-growth thin dielectric layers can be used to passivate both the top and bottom interfaces of Cu2ZnSnSe4 solar absorber, which has been drawing attention in the PV community as an earth-abundant, non-toxic and cheap solar material. The passivation strategy with the thin ALD-grown layers led to significant improvement in open-circuit voltage by suppressing charge recombination.[1] Another example of the ALD application in thin film PV is the replacement of CdS—the most common buffer layer in CIGS solar cells but with a toxic Cd—with ALD-ZnTiO.[2] I will present the application of ALD-ZnTiO whose materials properties were tuned In the PEC part, various metal oxide layers prepared by ALD were applied to Cu(In,Ga)Se2 (CIGS) photocathode as protection layers to prevent photo-corrosion of the CIGS in a liquid electrolyte.[3],[4] Different degradation mechanisms were identified for PEC devices with different ALD protective overlayers, details of which will be discussed. [1] Kim et al., Progress in Photovoltaics, 25 (2017), 4. [2] Hwang et al., ACS Applied Materials & Interfaces, 10 (2018), 20920. [3] Koo et al., ACS Applied Materials & Interfaces, 9 (2017), 5279. [4] Koo et al., Advanced Functional Materials, 28 (2018), 16.