Thermal Effect on the Electronic Properties of ZnO/CdS/CIGSeS Solar Cell at/near the Heterojunction Interfaces

Abstract

Hard X-ray photoelectron spectroscopy (HAXPES) was utilized to investigate the thermal effect on heterojunction interfaces of a commercial CIGSeS-based solar cell, especially for the variations in its electronic properties and diffusion behaviors of the elements. To obtain depth-dependent information near the ZnO/CdS/CIGSeS heterojunction interfaces using a nondestructive method, we deliberately prepared a series of CIGSeS solar cells annealed at different temperatures with wedge-like ZnO window layers from a chemical etching method and collected the photoelectrons emitted from the samples with a lateral scan. A quantitative analysis of the HAXPES results revealed that all elements were upwardly diffused, whereas the cadmium atoms in the CdS buffer layer remained unchanged after the thermal treatment. Thermal annealing resulted in the disappearance of the ordered defect compound (ODC) domain and the band realignment at the ZnO/CdS/CIGSeS interfaces due to elemental interdiffusion. Our results elucidate the dominant mechanism behind the heat-induced degradation of the efficiency of energy conversion.

The Overall-Efficiency Improvement of Flexible CIGSe Solar Cells by Two-Segment Process

“…In the realm of photovoltaic (PV) applications, copper-indium-gallium-selenide (Cu(In,Ga)Se2, CIGSe) stands out as a promising absorber material, characterized by its near-optimal bandgap, high optical absorption coefficients, and long-term stability [1]. Several studies have reported enhanced solar cell efficiency through the utilization of a CIGSe absorber in conjunction with various buffer layer materials [2][3][4][5]. In a CIGSe structure, when light enters the absorber layer, photons with energy according to their bandgap values can be absorbed by the absorbing layer as much as possible, thus reducing the amount of light loss [6].…”