Dimensionality-driven photovoltaic performance in CsPbBr3 perovskites: a comparative study of 3D, 2D, and 3D/2D interface architectures.

In this study, we investigate the structural, electronic, and optical properties of CsPbBr3 perovskite in its 3D bulk, 2D nanosheet, and 3D/2D interface configurations to evaluate their potential for high-efficiency optoelectronics. Structural analysis indicates that dimensionality reduction from the 3D cubic phase to the 2D/3D interface induces lattice relaxation, resulting in in-plane expansion. Electronic band structure and density of states calculations reveal that all three systems maintain a direct bandgap, with quantum confinement effects increasing the PBE bandgap from 1.64 eV in the 3D bulk to 2.11 eV in the 2D nanosheet, while the 3D/2D interface provides a balanced bandgap of 2.02 eV. Optical characterization shows that all phases exhibit strong absorption coefficients exceeding 106 cm-1 in the ultraviolet region, with the interface providing a hybridized dielectric response that optimizes photon management. The theoretical photovoltaic performance was evaluated using the Shockley-Queisser (SQ) limit, yielding efficiency ceilings of 16.29%, 7.03%, and 7.53% based on HSE06 without SOC for the 3D, 2D, and interface systems, respectively. Our results demonstrate that while the 3D phase offers the highest theoretical current harvesting, the 3D/2D interface represents a superior architectural choice by combining high voltage potential with the necessary structural stability and surface passivation for advanced perovskite solar cells.