Interface engineering and nanoscale characterization of Zn(S,O) alternative buffer layer for CIGS thin film solar cells

The buffer layers in Cu(In,Ga)Se₂ solar cells play a crucial role in device performance, although their thickness is only a few tens of nanometers. Moreover, often Zn(S,O) alternative buffer layers have been studied in view of their structure, band alignment, and optical properties, but not much work exists on their nanoscale chemical properties. This work focuses on the chemical characterization of Zn(S,O) using x-ray photoelectron spectroscopy for determination of the Zn(S,O) and Cu(In,Ga)Se₂ depth composition, and atom probe tomography for probing the nano-scale chemical fluctuations at the Zn(S,O)/Cu(In,Ga)Se₂ interface. The Zn(O,S) buffer layer was deposited by RF magnetron sputtering. The aim is to study the nanoscale concentration changes and atomic interdiffusion between CIGS and Zn(S,O) after sputter deposition at room temperature and after post-deposition heat treatment at 200°C.