On the Mechanism of Solvents Catalyzed Structural Transformation in Metal Halide Perovskites

2D Hybrid Perovskites: From Static and Dynamic Structures to Potential Applications

2D perovskites have received great attention recently due to their structural tunability and environmental stability, making them highly promising candidates for various applications by breaking property bottlenecks that affect established materials. However, in 2D perovskites, the complicated interplay between organic spacers and inorganic slabs makes structural analysis challenging to interpret. A deeper understanding of the structure-property relationship in these systems is urgently needed to enable high-performance tunable optoelectronic devices. Herein, this study examines how structural changes, from constant lattice distortion and variable structural evolution, modeled with both static and dynamic structural descriptors, affect macroscopic properties and ultimately device performance. The effect of chemical composition, crystallographic inhomogeneity, and mechanical-stress-induced static structural changes and corresponding electronic band variations is reported. In addition, the structure dynamics are described from the viewpoint of anharmonic vibrations, which impact electron-phonon coupling and the carriers' dynamic processes. Correlated carrier-matter interactions, known as polarons and acting on fine electronic structures, are then discussed. Finally, reliable guidelines to facilitate design to exploit structural features and rationally achieve breakthroughs in 2D perovskite applications are proposed. This review provides a global structural landscape of 2D perovskites, expected to promote the prosperity of these materials in emerging device applications.

Optimizing the Buried Interface in Flexible Perovskite Solar Cells to Achieve Over 24% Efficiency and Long-Term Stability

The buried interface of the perovskite layer has a profound influence on its film morphology, defect formation, and aging resistance from the outset, therefore, significantly affects the film quality and device performance of derived perovskite solar cells. Especially for FAPbI3 , although it has excellent optoelectronic properties, the spontaneous transition from the black perovskite phase to nonperovskite phase tends to start from the buried interface at the early stage of film formation then further propagate to degrade the whole perovskite. In this work, by introducing ─NH3 + rich proline hydrochloride (PF) with a conjugated rigid structure as a versatile medium for buried interface, it not only provides a solid α-phase FAPbI3 template, but also prevents the phase transition induced degradation. PF also acts as an effective interfacial stress reliever to enhance both efficiency and stability of flexible solar cells. Consequently, a champion efficiency of 24.61% (certified 23.51%) can be achieved, which is the highest efficiency among all reported values for flexible perovskite solar cells. Besides, devices demonstrate excellent shelf-life/light soaking stability (advanced level of ISOS stability protocols) and mechanical stability.

Crystal Growth Regulation of Ruddlesden-Popper Perovskites via Self-Assembly of Semiconductor Spacers for Efficient Solar Cells

The crystal growth and orientation of two-dimensional (2D) perovskite films significantly impact solar cell performance. Here, we incorporated robust quadrupole-quadrupole interactions to govern the crystal growth of 2D Ruddlesden-Popper (RP) perovskites. This was achieved through the development of two unique semiconductor spacers, namely PTMA and 5FPTMA, with different dipole moments. The ((5FPTMA)0.1 (PTMA)0.9 )2 MAn-1 Pbn I3n+1 (nominal n=5, 5F/PTMA-Pb) film shows a preferred vertical orientation, reduced grain boundaries, and released residual strain compared to (PTMA)2 MAn-1 Pbn I3n+1 (nominal n=5, PTMA-Pb), resulting in a decreased exciton binding energy and reduced electron-phonon coupling coefficients. In contrast to PTMA-Pb device with an efficiency of 15.66 %, the 5F/PTMA-Pb device achieved a champion efficiency of 18.56 %, making it among the best efficiency for 2D RP perovskite solar cells employing an MA-based semiconductor spacer. This work offers significant insights into comprehending the crystal growth process of 2D RP perovskite films through the utilization of quadrupole-quadrupole interactions between semiconductor spacers.