Universal approach toward high-efficiency two-dimensional perovskite solar cells via a vertical-rotation process

Abstract

The emerging 2D perovskites exhibit superior stability and similar optoelectronic attributes compared to 3D analogous, but their strong exciton-binding energy and inferior interlayer charge-transport reduce dramatically the device performance. Herein,...

Crystallization Kinetics in 2D Perovskite Solar Cells

“…Reproduced with permission. [ 131 ] Copyright 2020, Royal Society of Chemistry d) SEM images and schematic diagram of crystallization process of BA 2 MA 3 Sn 4 I 13 perovskite films fabricated from different solvents: a) single Lewis acid–base complex process, b) single ion exchange process, and c) cooperative process of Lewis acid–base complex and ion exchange. Reproduced with permission.…”

“…However, it is encouraging that Nazeeruddin and co‐workers recently elucidated the universal mechanism behind crystal‐aligning additives. [ 131 ] They proposed that the (202) crystal plane of perovskite has a higher adsorption energy for NH 4 Cl. When annealed at a certain humidity, water molecules (H 2 O) accelerate the deprotonation of NH 4+ due to the synergistic effect, which guides the 2D framework toward a vertical orientation (Figure 6c).…”

Defect Suppression in Oriented 2D Perovskite Solar Cells with Efficiency over 18% via Rerouting Crystallization Pathway

“…When the nucleus‐centered growth begins, neighboring regions reach each other very quickly and tend to form many tiny grain regions. As the solvent evaporates, NH 4 + gradually escapes from the film due to its easy deprotonation facilitated by ambient H 2 O, [ 16,27 ] releasing the (202) surface for further crystallization, and a perovskite film dominated by the (111) crystal plane is finally formed. Though NH 4 Cl enhances PbI 6 octahedral colloids’ solubility and inhibits the homogenous nucleations inside the solution to benefit the out‐of‐plane growth, this (111)‐governed secondary nucleation inevitably causes defective growth, small grains, and extensive grain boundaries.…”

“…[7] ii) The over-rapid kinetically controlled self-assembly of 2D perovskite nearly completes its crystallization after the spin-coating process without thermal annealing, which would generate numerous grain boundaries and defective growth. [8] Recent findings offer a range of solutions to address the problem of the highly chaotic system, such as designing new bulky organic ammoniums, [9][10][11][12] adopting the hot-casting technique, [1,6,13] decreasing the precursor supersaturation, [14,15] and applying functional additives, [16][17][18][19] which successfully promote the out-of-plane-oriented growth of 2D perovskite. However, up to now, there is still a lack of attention to the over-rapid crystallization-induced defects in those vertically oriented 2D perovskite films.…”

“…The Ruddlesden-Popper perovskite with (PEA) 2 (MA) 3 Pb 4 I 13 (PEA: phenethylammonium, MA: methylammonium) composition was mainly focused in this study. Considering the adsorption effect of the NH 4 Cl additive and its success in promoting the out-of-plane orientation of 2D perovskites, [7,16] the heavier iodide was incorporated into NH 4 Cl to reroute the crystallization pathway of vertically oriented 2D perovskite films. The entire stage of crystallization was investigated by comparing the time evolution of X-ray diffraction (XRD) patterns of three freshly spin-coated 2D perovskite films with NH 4 Cl, NH 4 I, and NH 4 I x Cl 1−x (Figure 1a-c), and the crystallization ratios of (111) to (202) (I 111/202 ) are summarized in Figure S1 (Supporting Information).…”