Stable, color-tunable 2D SCN-based perovskites: revealing the critical influence of an asymmetric pseudo-halide on constituent ions

Abstract

It is revealed that the linear SCN− anion dictates critical restriction on the constituent ions of its derived 2D (PbX4(SCN)2) framework.

Impact of Dimensionality on Optoelectronic Properties of Hybrid Perovskites

“…The characteristic PL lifetimes of CH 3 NH 3 PbI 3 at 773 nm are 1.9 ns (56%) and 7.8 ns (44%). These results [19,45].…”

“…This result also confirms that the emission at 600 nm is due to singlet exciton while the emission at the main peak (757 nm) is due to triplet excitons. The observation of very short PL emission lifetime of 600 nm peak and long lifetime PL emission lifetime of 757 nm peak indicates that the recombination in (CH 3 NH 3 ) 2 Pb(SCN) 2 I 2 is dominated by excitonic recombination, and the 757 nm peak is associated with triplet excitons [19]. It has also been reported that this peak may be related to triplet excitons or defective states [19].…”

“…The observation of very short PL emission lifetime of 600 nm peak and long lifetime PL emission lifetime of 757 nm peak indicates that the recombination in (CH 3 NH 3 ) 2 Pb(SCN) 2 I 2 is dominated by excitonic recombination, and the 757 nm peak is associated with triplet excitons [19]. It has also been reported that this peak may be related to triplet excitons or defective states [19]. The characteristic PL lifetimes of CH 3 NH 3 PbI 3 at 773 nm are 1.9 ns (56%) and 7.8 ns (44%).…”

“…Two-dimensional (2D) hybrid perovskites offer superior ambient stability along with local confinement, anisotropic dimensionality, and versatility of organic chemistry synthesis and flexibility for the modulation of optoelectronic properties [10][11][12]. Therefore, these systems are very promising alternatives to 3D perovskites for photovoltaic and lightemitting diode applications [13][14][15][16][17][18][19]. Most excitations in these 2D structures are excitons in contrast to free carriers in 3D perovskites and show contrasting properties compared to 3D structures [10].…”

Inorganic‐Cation Pseudohalide 2D Cs2Pb(SCN)2Br2 Perovskite Single Crystal

“…Such ε r is high compared to those (ε r = 3.3–15.1) of perovskite crystals with long‐chain organic barriers. [ 33–35 ] Such high dielectric constant would reduce the exciton binding energy E b due to the inverse square relationship. [ 36 ] We measured E b of 2D Cs 2 Pb(SCN) 2 Br 2 single crystal using temperature‐dependent PL (temp‐PL) (Figure S13a, Supporting Information).…”