Formation and electronic properties of the CdS/CuInSe2 (011) heterointerface studied by synchrotron-induced photoemission

Abstract

The heterointerface p‐CuInSe₂/CdS was investigated by soft x‐ray photoelectron spectroscopy. CdS was deposited sequentially in steps onto CuInSe₂ (011) cleavage planes at room temperature (RT) and at elevated temperatures (≳120 °C). At RT a nonreactive interface to cubic CdS is formed. The valence band and conduction‐band discontinuities are determined to be 0.8 and 0.7 eV, respectively. A band bending of 0.9 eV is deduced for the p‐type substrate. Annealing to temperatures above 120 °C leads to the formation of a Cu_xS reactive layer at the interface. As a consequence the valence‐band offset and band bending is found to be considerably reduced. The experimentally determined band energy diagram is in agreement with heterojunctions of zincblende‐type semiconductors, and its consequences for solar cells are discussed.