Estudo das propriedades estruturais e optoeletrônicas de Perovskitas ecológicas de haleto com baixa dimensionalidade

Abstract

In recent decades, Low-dimensional (2D) hybrid metal halide perovskites (MHPs) have emerged as promising semiconductors for next-generation photovoltaics. Despite their high environmental compatibility and excellent thermodynamic stability, lead-base materials represent significant risks to both the environment and human health. To overcome this barrier to commercialization, this work analises the impact of alternative inorganic lattice BX-based compositions (B = Ge or Sn; X = Br or I) on structural and optoelectronic properties. The investigated systems encompasses 2D Ruddlesden- Popper MHPs, BA2MAn+1BnX3n+1 (for 1 to 5 layers), and the 3D bulk (MA)BX3 (where BA = butylammonium and MA = methylammonium), employing ab initio calculations with spin-orbit coupling (SOC), quasiparticle DFT-1/2, and van der Waals corrections (D3). Preliminary results unveil how ionic radii induce anisotropy internal and external distortions within the organic and inorganic lattices. Similarly, BA spacers influenced local distortion and widens band gaps. We then analyzed the excitonic and optical response properties of BA2SnI4 using a computational protocol integrating ab initio and semi-empirical approaches. A robust yet cost-effective workflow was employed, combining maximally localized Wannier functions via the tight-binding method (MLWFTB) to describe electronic states within the independent particle approximation (IPA) and Bethe-Salpeter equation (BSE) frameworks, while maintaining the same ab initio protocol and corrections. Our findings reveal that replacing Pb with Sn enhances excitonic properties and charge extraction efficiency, positioning BA2SnI4 as a promising photovoltaic material capable of achieving power conversion efficiency (PCE) values near 25% in ultrathin films (< 0;25 μm). Compared to IPA, BSE predictions revealed a red-shift in optical absorption, extending the spectral response further into the visible spectrum. This protocol enables a characterization of 2D perovskites, paving the way for eco-friendly alternatives to Pb-based materials. However, despite these advantageous features, further work is required to resolve manufacturing issues and enchance performance stability.