Shuaifeng Hu

Abstract:

Abstract:

The properties of metal‐centred species in metal halide perovskite precursor solutions substantially influence the formation and evolution of colloidal particles, which in turn dictate the crystallisation process and the film quality. In this work, we assess the “hard” and “soft” Lewis acid characteristics of Sn2+ and Pb2+ cations as a strategy to modulate the chemical environment of these metal‐containing species in mixed‐metal tin–lead perovskite precursor solutions. We observe enhanced simultaneous access to both metal centres upon adding compounds with functional groups suggested by the hard–soft acid–base principle. Theoretical calculations suggest that the hard base carboxyl group preferentially interacts with Sn2+‐based species, while the softer base thiol group also targets Pb2+‐based species. By effectively accessing and manipulating possible classes of inorganic species and their colloidal particle properties in the precursor solutions, we achieve 1.26 eV perovskite polycrystalline films exhibiting enhanced structural and optoelectronic quality, giving the best quasi‐Fermi level splitting values of up to 0.95 eV. As a result, the solar cell devices demonstrate efficiency values of up to 23.3% with an extended operational lifetime, retaining 80% of their initial efficiency after over 280 and 180 h of maximum power point tracking under simulated AM1.5G illumination at 25 and 65 °C, respectively.

Abstract:

Thanks to their superior bandgap tunability and high absorption coefficient, metal halide perovskites demonstrate high potential for fabricating multijunction photovoltaics capable of achieving power conversion efficiencies surpassing the radiative efficiency limit of single-junction solar cells[1],[2]. One of the key challenges currently facing all-perovskite multijunction photovoltaics is the low quality of the narrow bandgap (~1.25 eV) mixed tin-lead perovskite films used as the rear absorber. At this conference, we will present our recent investigations on the mixed tin−lead perovskites covering the control of the Sn(II) oxidation[3], interface carrier extraction[4], and in-situ surface reaction[5], as well as the understanding of the solution chemistry and resultant crystallization[6], aiming to generate a global picture toward the comprehensive understanding of this material and its photovoltaic devices. As a result, we have obtained efficiencies of over 23.9% for the single-junction tin−lead perovskite devices, with an open circuit voltage of up to 0.91 V. Building on optimizations of neat lead perovskites, we then showcase the successful integration of these improved mixed tin-lead perovskites into double-, triple-, and quadruple-junction tandem solar cells, achieving efficiencies exceeding 29%, 28%, and 27%, respectively. In addition, we will propose promising strategies for enhancing the light and temperature stability of the involved perovskite subcells, aiming to improve the reliability of efficient all-perovskite multijunction photovoltaics. Furthermore, we will also share insights and recent progress achieved in perovskite-on-silicon multijunction cells.

Abstract:

While (111)-dominated perovskite films hold the potential for high-stability solar cells, most studies have primarily focused on modulating the (111) facets, overlooking the distribution and formation mechanism of the nondominant (100) facets. In this study, we delve into the (111) orientation via solvent regulation and investigate the evolution of facet distribution using various diffraction techniques. The findings reveal that simply stacking (111) facets does not inherently enhance solar cells. Instead, the distribution of nondominant (100) facets in (111)-dominated films significantly influences both photoelectric property and stability. These observations highlight the critical need to manage the interplay between dominant and nondominant facets. The study further offers strategies for addressing facet heterogeneity to achieve a uniform facet distribution. This research provides a comprehensive framework for understanding (111)-dominated perovskites and offers valuable guidance for designing high-performance perovskite solar cells.

Abstract:

Metal-halide perovskites are emerging as promising semiconductors for next-generation (opto)electronics. Due to their excellent optoelectronic and physical properties, as well as their processing capabilities, the past decades have seen significant progress and success in various device applications, such as solar cells, photodetectors, light-emitting diodes, and transistors. Despite their performance now rivaling or surpassing that of silicon counterparts, halide-perovskite semiconductors still face challenges for commercialization, particularly in terms of toxicity, stability, reliability, reproducibility, and lifetime. In this Roadmap, we present comprehensive discussions and perspectives from leading experts in the perovskite research community, covering various perovskite (opto)electronics, fundamental material properties and fabrication methods, photophysical characterizations, computing science, device physics, and the current challenges in each field. We hope this article provides a valuable resource for researchers and fosters the development of halide perovskites from basic to applied science.