Asymmetric Diammonium Directed In-Plane Charge Transport Enhancement in Two-Dimensional Lead Bromide Perovskite for Weak-Light Detection

Abstract

Two-dimensional (2D) Dion-Jacobson (DJ) perovskites are drawing significant attention in optoelectronic fields because of their enhanced out-of-plane electron coupling and improved structure stability. However, the structural effects of organic cations on the in-plane charge transport properties of 2D DJ lead bromide perovskites have remained less explored. Herein, we adopt asymmetric 3-(dimethylamino)-1-propylammonium (DMPD) and symmetric butane-1,4-diammonium (BDA) to systematically investigate the influence of organic cations on the structural, optical, and in-plane charge transport properties of 2D lead bromide perovskites. The large penetration depth of DMPD 2+ induces a decreased perovskite layer distortion and a lower bandgap in DMPDPbBr 4 , compared with that of BDAPbBr 4 . Moreover, DMPDPbBr 4 is shown to possess a low exciton binding energy, a low defect density, and a low ion migration activation energy, thereby yielding a more efficient in-plane charge collection efficiency than BDAPbBr 4 . Density functional theory calculations suggest that the improved in-plane charge transport can be traced to the enlarged antibonding coupling between Pb−6s and Br−4p orbitals that enables a high band dispersion and a low carrier effective mass in the in-plane direction of DMPDPbBr 4 . Finally, the planar Ag/ DMPDPbBr 4 /Ag photodetector delivers a satisfying detectivity of 1.73 × 10 12 Jones under an incident power intensity of 0.16 mW cm −2 and a high on/off ratio of 5.3 × 10 3 . The above findings offer novel insight for the design of 2D DJ lead bromide perovskites for optoelectronic devices.

Establishing a Relationship between the Bandgap and the Structure in 2D Lead Halide Perovskite Semiconductors

“…The theoretical E g data of 3 , 5 , and 7 accord with the experimental values (Figure a,e,i). It is shown that the orbital interactions between the Pb and Br ions dominate the valence band level and a small Pb–Br octahedron distortion corresponds to a small E g . That means the D d decreases when the bridging Br ion locates near the center of adjacent Pb ions so that the Br-4p orbitals are close to the straight line connecting the adjacent Pb ions.…”

“…It is shown that the orbital interactions between the Pb and Br ions dominate the valence band level and a small Pb−Br octahedron distortion corresponds to a small E g . 60 That means the D d decreases when the bridging Br ion locates near the center of adjacent Pb ions so that the Br-4p orbitals are close to the straight line connecting the adjacent Pb ions. Therefore, the increased overlap of Pb-6s and Br-4p orbitals leads to a reduced E g .…”

Centimeter-sized novel two-dimensional organic lead–tin mixed iodide single crystals for efficient photodetector applications

“…49,50 In addition, the σ 0 values of the title crystals were lower than that of some 2D perovskite single crystals, such as Rb 3 Bi 2 I 9 (8.43 × 10 10 cm −2 ) 51 and (Gua) 3 Bi 2 I 9 (3.35 × 10 10 cm −2 ). 52 Also, remarkably, after Sn alloying, the μ was effectively enhanced, which should be ascribed to the likelihood that more charge carriers in the 2D perovskite were thermally activated, and a proportion of free charge was also involved. 53 Both the increased carrier mobility and decreased trap states suggest a reduced non-radiative recombination loss for the crystals, which is beneficial for photoelectric applications.…”

Incorporating an Aromatic Diammonium To Assemble Bilayered Dion–Jacobson Perovskite Crystals for Weak Light Detection

“…27 [DMPD is 3-(dimethylamino)-1-propylammonium], which is constructed by the asymmetric diammonium cations and delivered a detectivity of 1.73 × 10 12 Jones under a light power intensity of 0.16 mW/cm 2 . 28 Although some photodetection works based on a DJ hybrid perovskite single crystal have been reported so far, however, most reported single-crystal devices based on DJ hybrid perovskites are usually constructed by aliphatic diammonium and showed relatively poor weak light detection ability, with a detection limit of around μW/ cm 2 . 29−31 Therefore, the research on DJ hybrid perovskites constructed by aromatic diammonium used for weak light detection is still rare, especially for the photodetection at the level of nW/cm 2 .…”

“…In addition, a bilayered DJ hybrid perovskite crystal (HDA)­CsPb 2 Br 7 (HAD is 1,6-hexamethylenediammonium) was developed by Sun’s group, who studied its photoactivities under 3 mW/cm 2 polarized light, with the detectivity of 1.5 × 10 9 Jones achieved in the crystal-based device . Recently, Chen et al reported a 2D DJ hybrid perovskite (DMPD)­PbBr 4 [DMPD is 3-(dimethylamino)-1-propylammonium], which is constructed by the asymmetric diammonium cations and delivered a detectivity of 1.73 × 10 12 Jones under a light power intensity of 0.16 mW/cm 2 . Although some photodetection works based on a DJ hybrid perovskite single crystal have been reported so far, however, most reported single-crystal devices based on DJ hybrid perovskites are usually constructed by aliphatic diammonium and showed relatively poor weak light detection ability, with a detection limit of around μW/cm 2 . − Therefore, the research on DJ hybrid perovskites constructed by aromatic diammonium used for weak light detection is still rare, especially for the photodetection at the level of nW/cm 2 .…”