First-principles investigation of multi-doped La₉Al₉O₂₇ (Zn, Cd, In) systems: Tailoring structural, electronic, mechanical and optical properties for advanced optoelectronic devices

LaAlO 3 -based perovskites have gained significant attention due to their tunable band gaps and environmentally friendly responses, making them potential candidates for advanced optoelectronic devices. In this work, we demonstrate an effective strategy that combines atomic doping with structural-stability enhancement to boost the electronic response of La 9 Al 9 O 27 under high-absorption optoelectronic operating conditions. Density functional theory was used to investigate the structural, electronic, mechanical and optical properties of the pristine and doped La 9 Al 9 O 27 system. The Al site was substituted with mono-, bi-, and tri-metallic dopants, resulting in configurations such as La 9 Al 8.5 Cd 0.5 O 27 , La 9 Al 8.5 Zn 0.5 O 27 , La 9 Al 8.5 In 0.5 O 27, La 9 Al 8 Cd 0.5 In 0.5 O 27, La 9 Al 8 Zn 0.5 In 0.5 O 27 and La 9 Al 8 Cd 0.5 Zn 0.5 In 0.5 O 27 . These systems were investigated using the generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional. The incorporation of the La 9 Al 8 Zn 0.5 In 0.5 O 27 dopant induced significant improvements in lattice parameters and volume, positively affecting structural stability. The calculated band gap of the La 9 Al 8 Cd 0.5 Zn 0.5 In 0.5 O 27 -doped system decreased from 3.03 eV to as low as 0.003 eV, indicating enhanced electronic conductivity, in strong agreement with theoretical and experimental data. The mechanical stability results further confirm the high stiffness and ductile behaviour of the bi-metallic (La 9 Al 8 Cd 0.5 In 0.5 O 27 ) and trimetallic (La 9 Al 8 Cd 0.5 Zn 0.5 In 0.5 O 27 ) doped materials, supported by Pugh ratios (B/G) of 2.19 and 2.05, and Poisson’s ratios of 0.30 and 0.28, respectively. Optical response evaluated in the 0–40 eV energy range displays high absorption coefficients and significant optical conductivity, indicating promising optoelectronic performance. These simulation-based findings presented here provide valuable insights into the effects of mono-, bi-, and trimetallic doping on La 9 Al 9 O 27 , facilitating advancements in designing materials for future optoelectronic devices. • DFT-GGA (PBE) calculations reveal comprehensive insights into La₉Al₉O₂₇ and its Cd, Zn, and In doped counterparts. • Mono-, bi-, and tri-metallic doping significantly reduce the band gap from 3.03 eV to 0.003 eV, enabling p-type conductivity. • Mechanical analysis confirms enhanced ductility and structural stability through elastic moduli and B/G ratios. • Optical studies across 0–40 eV energy range demonstrate strong potential for optoelectronic and photovoltaic applications.