Title : Size-dependent structural, electronic, and optical properties of hydrogen-passivated wurtzite InP quantum dots: A density functional theory study

Quantum dots (QDs) are highly promising for optoelectronic applications due to their size-tunable optical properties, narrow emission, and high photoluminescence quantum yield. In this study, density functional theory (DFT) was employed to investigate the size-dependent electronic and optical properties of wurtzite-core, hydrogen-passivated indium phosphide (InP) QDs ranging from 1.0 to 1.53 nm in diameter. Structural analysis reveals that QD stability increases with size. Electronic calculations demonstrate strong quantum confinement, with the energy gap narrowing from 2.71 eV to 2.01 eV as dot size increases, accompanied by a denser electronic density of states with balanced indium and phosphorus contributions that signify strong covalent bonding. Optically, static polarizability rises sharply from 141 to 437 ų with increasing diameter. Furthermore, investigation of point defects in the largest QD shows that a missing phosphorus atom creates a localized trap state that lowers the energy gap, whereas a missing indium atom forms a more spread-out trap state that slightly raises the gap; unpassivated QDs fail to reach structural stability. Overall, these findings elucidate how size, surface passivation, and intrinsic defects govern the properties of InP QDs, offering valuable theoretical guidance for designing advanced photovoltaic and optoelectronic materials.

I am Shanto Babu Das, a Physics graduate from Shahjalal University of Science and Technology with a strong interest in materials science, renewable energy, and computational physics. My research focuses on perovskite solar cells, InP/ZnS quantum dots, Density Functional Theory, and machine learning for materials science. I have hands-on experience in material synthesis, characterization, photovoltaic device fabrication, and simulation using advanced computational and experimental techniques. I am proficient in Python, scientific computing, SCAPS-1D, Quantum Espresso, and CASTEP. Alongside research, I actively contribute to physics education and scientific communities through leadership, volunteering, tutoring, and conference presentations.