Abstract:
Two-dimensional (2D) alternating cation (ACI) type perovskites self-assemble in solution to form highly ordered periodic stacks with unique physical properties and improved optoelectronic devices. Tailoring composition and distribution of quantum wells (QWs) is of vital importance for the optoelectronic properties and stability, which however, have been less reported in contrast to their Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) counterparts. Here, we propose crystallization control via solvent engineering for ACI perovskite (GA)MAnPbnI3n+1 (<n> = 5, GA = guanidinium, MA = methylammonium) that enable preferential QW distribution within the film and augment the crystallinity and smoothness of the films. It is found that such morphological improvements were further reflected in the optoelectronic properties, including enhanced charge carrier transport/extraction and suppressed nonradiative charge-recombination. Thus, we realize efficient and stable ACI perovskite solar cells with a power-conversion-efficiency (PCE) of 19.18%, standing the highest among all reported RP, DJ and ACI (<n> ≤ 5) solar cells. Meanwhile, the device exhibited superior reproducibility and environmental stability. These findings highlight the importance of crystallization control and pave the way for the realization of high-performance 2D perovskite solar cells.

DOI: 10.1002/solr.202100286