Ultraviolet active novel chalcogenides BAlTe2 (B = Rb, Cs): the structural, optoelectronic, mechanical, and vibrational properties for energy harvesting applications through first principles approach

In this study, ternary aluminum-based chalcogenide materials are discussed since these are found to be very appealing for multifunction devices. Here, the structural, optoelectronic, mechanical, and vibrational properties of RbAlTe₂ and CsAlTe₂ are observed via density functional theory (DFT). An indirect energy band gap is noted to be increased from 1.33 eV to 1.96 eV for RbAlTe₂ and 1.28 eV to 1.83 eV for CsAlTe₂ by employing improved functional as modified by Trans and Blaha. The calculated formation energy appears to be decreasing, such as -4.39 and -3.83 eV for RbAlTe₂ and CsAlTe₂, respectively. The investigation of PDOS revealed that Rb-d, Cs-p, Al-p/s, and Te-p orbitals are located prominently and contribute mainly to boosting the conduction mechanism. The optical results declare CsAlTe₂ as the strongest absorptive substance, which may be used to devise optoelectronic and photovoltaic devices. Moreover, six independent elastic constants show that these are mechanically stable materials, their brittle nature is confirmed by obeying Born’s stability requirements. According to the density functional perturbation theory (DFPT) approach used for analyzing phonon dispersion, there is no imaginary phonon frequency in both cases (RbAlTe₂ and CsAlTe₂). The overall results show that the studied materials are potential candidates for applications in photovoltaic and optoelectronic devices.