# How ALD Settings May Affect the Chemical Structure of the (Zn1–x Sn x )O y /Wide-Gap (Ag,Cu)GaSe2 Thin-Film Solar Cell Interface

## TL;DR

This study shows how different ALD settings affect the chemical structure and performance of thin-film solar cells.

## Contribution

The discovery of a ZnO-Ga2O3 interlayer formed during industrial-scale ALD and its impact on solar cell performance.

## Key findings

- An interlayer of ZnO with minor Ga2O3 forms during industrial-scale ALD but not in lab-scale reactors.
- Solar cells with this interlayer have significantly lower fill factors due to an electron transport barrier.

## Abstract

In this work, the effect of different atomic layer deposition
(ALD)
settings on the interface formation between ALD-grown (Zn1–x
Sn
x
)­O
y
(ZTO) buffers with varying [Sn]/([Sn]+[Zn]) composition and
wide-band gap silver-alloyed CuGaSe2 (ACGSe) absorbers
is investigated using X-ray fluorescence, transmission electron microscopy,
and synchrotron-based soft and hard X-ray photoelectron spectroscopy.
For buffer layers prepared in an industry-scale ALD reactor, we discover
the formation of an interlayer best described by a mixture of ZnO
with a minor (<10%) amount of Ga2O3, which
is not present in similar layer stacks prepared in a lab-scale R&D-type
ALD reactor. In addition, we show that ZTO/ACGSe-based solar cells
containing such an interlayer have significantly lower fill factors
compared to their counterparts without this interlayer, suggesting
the presence of an electron transport barrier at the front contact.