Beschreibung:
<jats:sec><jats:label /><jats:p>The Cu<jats:sub>2</jats:sub>ZnGe<jats:sub>
<jats:italic>X</jats:italic>
</jats:sub>Sn<jats:sub>1‐<jats:italic>X</jats:italic>
</jats:sub>S<jats:sub>4</jats:sub> (CZGTS) thin‐film solar cells have a limited open‐circuit voltage (<jats:italic>V</jats:italic>
<jats:sub>OC</jats:sub>) due to bulk and interface recombination. Since the standard CdS buffer layer gives a significant cliff‐like conduction band offset to CZGTS, alternative buffer layers are needed to reduce the interface recombination. This work compares the performance of wide bandgap Cu<jats:sub>2</jats:sub>ZnGeS<jats:sub>4</jats:sub> (CZGS) solar cells fabricated with nontoxic Zn<jats:sub>
<jats:italic>x</jats:italic>
</jats:sub>Sn<jats:sub>1–<jats:italic>x</jats:italic>
</jats:sub>O<jats:sub>
<jats:italic>y</jats:italic>
</jats:sub> (ZTO) buffer layers grown by atomic layer deposition under different conditions. The <jats:italic>V</jats:italic>
<jats:sub>OC</jats:sub> of the CZGS solar cell improved significantly to over 1 V by substituting CdS with ZTO. However, <jats:italic>V</jats:italic>
<jats:sub>OC</jats:sub> is relatively insensitive to ZTO bandgap variations. The short‐circuit current is generally low but is improved with KCN etching of the CZGS absorber before deposition of the ZTO buffer layer. A possible explanation for the device behavior is the presence of an oxide interlayer for nonetched devices.</jats:p></jats:sec>