Molecular Engineering of 1D Hybrid Perovskites for Improving the Performance and Stability of Metal Halide Perovskite Solar Cells

Description

Compared to other thin-film technologies, metal halide perovskite-based solar cells (PSCs) have demonstrated a much higher power conversion efficiency (PCE) of 25.5% based on simple solution processing of perovskite materials. However, it is still below the theoretical values predicted by the Shockley-Queisser limit. The nonradiative recombination loss originated from the lattice defects on bulk, surfaces, and interfaces of perovskites in the active layer is a key barrier to further improve the efficiency. Currently, two-dimensional (2D) hybrid perovskites with large hydrophobic organic cations are employed as the capping layer for defect passivation of three-dimensional (3D) perovskites.  However, the complex electronic states adversely introduced by the heterogeneous 2D perovskite quantum wells during solution processing can be a significant source of energy loss in PSCs since charge carriers can be trapped in these states to reduce their mobilities and result in increased nonradiative recombination. These passivation-induced states are mainly associated with the varied conformations and impure phase distributions (n number) of 2D perovskites. Therefore, suppressing the complex electronic states by controlling the phase purity and thickness of the passivation layer would reduce carrier traps and mitigate carrier dynamics at the interfaces. It would be ideal to develop alternative passivation strategies that do not introduce passivation-induced defects while can enhance the performance and stability of resultant PSCs. In this proposal, we will (1) conduct rational design and synthesis of new classes of 1D perovskites for passivating the surface and interfacial defects of 3D perovskites to improve the performance and stability of PSCs; (2) study and tailor systematically the molecularstructures of organic cations for 1D perovskites to achieve proper band alignment for mitigating the charge extraction and collection dynamics at perovskite interfaces; (3) develop cross-linkable 1D hybrid perovskites that are external stimuli responsive to enhance thestability of passivated perovskites and devices; (4) conduct comprehensive optical, electrochemical, and photo-physical characterization of passivated 3D perovskites and carry out crystallographic and morphological studies of derived 1D perovskite structures and 3D perovskite films to understand the structure/property relationships of resultant materials; (5) demonstrate high-performance PSC with > 27% PCE at the end of project based on the new 1D hybrid perovskites and optimal perovskite compositions developed. The results generated from this project will provide guidance for developing future highly efficient and stable PSCs.It will also establish Hong Kong at the forefront of research and development for printable perovskite solar cells based low-cost clean energy.