The inequivalent substitution on Ca site of cubic CaTiO3 perovskite for transparent conductive oxides from USPEX and DFT

TL;DR

This study uses USPEX and DFT to explore how substituting Ca in CaTiO3 affects its electronic properties, aiming to develop p- and n-type transparent conductive oxides with stable structures.

Contribution

It demonstrates the use of genetic algorithms and DFT to predict stable structures and electronic properties of CaTiO3 with various substitutions for TCO applications.

Findings

Na substitution induces p-type behavior without oxygen vacancies.

Al substitution results in n-type conductivity with tetragonal phase.

p-type Ca0.75Na0.25TiO3 shows higher mobility than n-type.

Abstract

Based on genetic evolution algorithm, universal structure predictor USPEX assists to explore the most stable structure from Na+ substituting Ca2+ under variable concentration, for p type transparent conductive oxide application. The study finds 2 atoms of NaCa maintain the octahedral packing and cubic phase without the presence of oxygen vacancy, but the electron loss causes in fermi level entering into valence band, realizing p type TCOs character. While others still remain insulator character due to the compensation of oxygen vacancy. Applying Al3+ substituting Ca2+ achieve the fermi level into conduction band with n-type TCOs, with the symmetry of tetragonal phase. And the transport properties for p- type Ca0.75Na0.25TiO3 and n-type Ca0.75Al0.25TiO3 are calculated, the mobility in p- type Ca0.75Na0.25TiO3 is more superior owing to its curvature edge.