High-pressure study of the structural phase transition in Cu1.875Te

Abstract Cu2−xTe is mainly used as conductive back contacting material in CdTe solar cells. Unavoidable Cu deficiency has traditionally been considered as the primary cause of structural complexity, which limited its practical applicability. Here, combining X-ray diffraction (XRD) measurement with extensive swarm structure search, we identify the ambient structure of Cu1.875Te to be a P-3m1 phase, which transforms into a new defective I4/mmm phase at 2.9 GPa. Enthalpy calculations show that stoichiometric Cu2Te is expected to be synthesized above 5.3 GPa. The analysis of mechanical and dynamical stability implies that the high-pressure I4/mmm Cu2Te can potentially be stabilized to ambient conditions as a metastable material. Our results represent a significant step in understanding the crystal information of Cu2−xTe.