Strain modulating electronic band gaps and SQ efficiencies of semiconductor 2D PdQ₂ (Q = S, Se) monolayer

We studied the physical, electronic transport and optical properties of a unique pentagonal PdQ₂ (Q = S, Se) monolayers. The dynamic stability of 2Dwrinkle like-PdQ₂ is proven by positive phonon frequencies in the phonon dispersion curve. The optimized structural parameters of wrinkled pentagonal PdQ₂ are in good agreement with the available experimental results. The ultimate tensile strength (UTHS) was calculated and found that, penta-PdS₂ monolayer can withstand up to 16% (18%) strain along x (y) direction with 3.44 GPa (3.43 GPa). While, penta-PdSe₂ monolayer can withstand up to 17% (19%) strain along x (y) dirrection with 3.46 GPa (3.40 GPa). It is found that, the penta-PdQ₂ monolayers has the semiconducting behavior with indirect band gap of 0.94 and 1.26 eV for 2D-PdS₂ and 2D-PdSe₂, respectively. More interestingly, at room temperacture, the hole mobilty (electron mobility) obtained for 2D-PdS₂ and PdSe₂ are 67.43 (258.06) cm² V^-1 s^-1 and 1518.81 (442.49) cm² V^-1 s^-1, respectively. In addition, I-V characteristics of PdSe₂ monolayer show strong negative differential conductance (NDC) region near the 3.57 V. The Shockly-Queisser (SQ) effeciency prameters of PdQ₂ monolayers are also explored and the highest SQ efficeinciy obtained for PdS₂ is 33.93% at -5% strain and for PdSe₂ is 33.94% at -2% strain. The penta-PdQ₂ exhibits high optical absorption intensity in the UV region, up to 4.04 × 10⁵ (for PdS₂) and 5.28 × 10⁵ (for PdSe₂), which is suitable for applications in optoelectronic devices. Thus, the ultrathin PdQ₂ monolayers could be potential material for next-generation solar-cell applications and high performance nanodevices.