Pressure-tailored band gap reduction of Sr3NBr3 compound for optoelectronic application: a first-principles investigation
Nusrat Jahan Nisha, Md Saiduzzaman, Md. Bayjid Hossain Parosh, Istiak Ahmed Ovi
Abstract
• The band gap of Sr 3 NBr 3 decreases significantly under pressure which enhances absorption. • The compound Sr 3 NBr 3 remains mechanically stable up to 30 GPa pressure. • Optical properties are tuning with applied pressure, and shifting absorption coefficient. • High thermal conductivity and melting temperature demonstrate stability under extreme conditions. • Apart from the GGA-PBE functional, other functionals are used to calculate the band gap accurately. Sr 3 NBr 3 is an inorganic halide perovskite with a cubic structure. The comprehensive analysis of structural, electronic, optical, mechanical, and thermal properties of Sr 3 NBr 3 makes it suitable for possible optoelectronic devices and solar cell applications. This study demonstrates the impact of applied pressures of 0 GPa to 30 GPa on Sr 3 NBr 3 using DFT calculations. The compound Sr 3 NBr 3 has a band gap of 1.077 eV (GGA) / 1.515 eV (HSE06) at the Γ-point at zero pressure (0 GPa). When the pressure is increased to 30 GPa, the band gap decreases to 0.358 eV (GGA) / 0.771 eV (HSE06), showing that pressure reduces the band gap in the material. The compound shows direct electronic bandgaps, which are analyzed using the GGA-PBE, GGA-WC, GGA-PBESol, and Hybrid-HSE06 functionals. As well, the band gap of the compound changes under increased pressure. Compressive pressure reduces the band gap so that more visible light can be absorbed. These stable lattice dynamics also enhance its applicability for high-pressure conditions. Sr 3 NBr 3 remains stable under high pressure as it meets the Born stability criteria at all pressures, with its elastic constants, bulk modulus, and shear modulus indicating strong resistance to deformation, compression, and shear stress. The band gap narrows under pressure due to structural compression, which decreases the lattice constant and enhances charge carrier motion, resulting in a reduced direct band gap. Under 30 GPa applied pressure, the electronic structure enhances its photovoltaic-relevant properties with improved light-harvesting efficiency and charge separation. These changes are manifested in the dielectric function and absorption coefficient that vary under compression to provide application-specific tunability. Within the pressure range of up to 30 GPa, Sr 3 NBr 3 demonstrates high thermal conductivity (K min ), an elevated Debye temperature (θ D ), and a higher melting temperature (T m ), making it well-suited for applications under extreme pressure. The data show that the physical properties of Sr 3 NBr 3 , like mechanical stability, are crucial for its use in solar cells, photodetectors, and optoelectronics. Pressure can be used to fine-tune these properties.