Recently, low-dimensional RuddlesdenâPopper
(LDRP) perovskite-based
solar cells (PSCs) have been extensively studied because of their
robust stability. However, because of the poor conductivity of the
organic spacer, the charge transport across the spacers in the LDRP
perovskite is considerably poor, and thus regulation of the growth
orientation of LDRP cells is of primary importance. So far, the key
role of organic cations in controlling the growth orientation of LDRP
films has been widely studied, but the impact of halogens has not
been sufficiently investigated. Herein, we demonstrate the important
role of halogens in determining the characteristics of benzylamine
(BZA)-based LDRP perovskite films, where different BZAX salts (X =
Cl, Br, I) are adopted. Compared to Br and I, Cl is shown to prominently
enlarge the grain size, promote the vertical orientation, reduce the
trap state density, and prolong the carrier lifetime of LDRP film,
and all these merits effectively accelerate the carrier transport
within the film. As a result, a PSC device based on BZACl delivers
a champion PCE of 17.25% with much improved device stability. This
work unravels the vital role of Cl in regulating the crystallization
process of LDRP films, which provides a facile approach for boosting
the performance of LDRP-based PSCs.