Electronic Structure and Doping Processes in Novel Semiconductor Materials

Abstract

Photoactive materials spark interest for areas such as solar energy conversion, photo-catalytic energy production, efficient light displays, or control of quantum-mechanical spin phenomena by light. This dissertation work centers on two classes of materials, chalcogenides and metal halide perovskites, chosen for their promise in light-interactive applications. Current research on these novel semiconductors is focused on overcoming challenges in detailed material design. Tuning strategies, including manipulation of chemical composition, dimensionality, and structural distortions, stand as exciting opportunities for modulating electronic and spin properties. These avenues for advancement necessitate a deep understanding of the complex physics that underlies material behavior, calling for density functional theory (DFT) simulations to capture intricate electronic structures and complex particle interactions.This dissertation work therefore employs DFT simulations to focus specifically on electronic structure and defects in efforts to strengthen our understanding of structure-property relationships in chalcogenide and perovskite semiconductors. The ability to tune energy band gaps and spin splitting via Se-alloying in the 3D chalcogenide, CuPbSbS3 is demonstrated. Next, transferred symmetry breaking from chiral organics to inorganic-sublattices, and resultant impact to electronic and spin properties is reported in hybrid organic-inorganic metal-halides. Following this, DFT strategies are employed to study H-bonding in a 2D hybrid perovskite, (2-BrPEA)2PbI4, uncovering (i) strategies to improve H-bonding analyses and (ii) formation mechanisms of spin-related properties. Finally, the potential for electronic doping via introduction of impurities in the 2D hybrid perovskite, PEA2PbI4, is examined. DFT calculations uncover the most promising candidates for extrinsic n- and p-type dopants, alongside formation mechanisms of defect complexes and compensating defects.