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

Abstract

Hybrid lead halide perovskites have been intensively investigated due to their structural diversity and outstanding optoelectronic properties. As emerging semiconducting materials, their bandgaps play a key role in regulating the performance. Qualitative correlations between the bandgap and structure have been uncovered; however, quantified relationships have not yet been established. Herein, we report a series of hydrogen-bonded quasi-Dion–Jacobson (DJ) perovskite semiconductors, [(HOOC n H2n–2NH3)2]PbBr4 (n = 3–8), as a model system to set up a more clear relationship between the structural distortions and optoelectronic properties. When the n ranges from 4 to 8, the serial compounds are featured by distinctive hydrogen-bonded diammonium layers containing dimerized COOH linkers and balanced photoluminescent and photodetection properties. A linear relationship between the bandgap (E g) and two structural parameters (D int and D d) is set up, that is, E g = 2.694 + 0.004680D int + 0.3109D d, indicating the roles of both the interlayer distance and inorganic framework distortion. This work not only expands the typical DJ-type perovskites but also provides a deepened understanding of the relationship between the structures and optoelectronic properties.

Room-Temperature Anisotropic Actuation Driven by a Synergistic Order–Disorder and Displacive Phase Transition in a Ferroelectric Crystal

“…Moreover, as a semiconductor, 1 shows optoelectronic responses to visible light (Figure S13). The DFT calculations reveal that 1 is a direct bandgap semiconductor of 3.02 eV in the LTP, consistent with the value of 2.89 eV, which was extracted from the UV–vis absorption spectra by using the Kubelka–Munk equation . The valence band maximum is composed of Pb-6s and I-5p orbitals overlapping, and the conduction band minimum is composed of the Pb-6p orbitals overlapping.…”

“…The DFT calculations reveal that 1 is a direct bandgap semiconductor of 3.02 eV in the LTP, consistent with the value of 2.89 eV, which was extracted from the UV−vis absorption spectra by using the Kubelka−Munk equation. 65 The valence band maximum is composed of Pb-6s and I-5p orbitals overlapping, and the conduction band minimum is composed of the Pb-6p orbitals overlapping. Thus, it is allowed to generate photogenerated carriers and transport along the 1D inorganic chains (Figure S14).…”

Polar Bilayered Dion–Jacobson Hybrid Perovskite Single Crystal with Bulk Photovoltaic Effect for Self-Driven X-ray–Ultraviolet–Visible Photodetection

“…For example, Priya's group reported a series of quasi-2D RP-type halide perovskite single-crystal photodetectors based on (C 4 H 9 NH 3 ) n (CH 3 NH 3 ) n−1 Pb n I 3n+1 (n = 1, 2, 3, 4, and ∞), which show a higher on/off ratio of 10 4 . 22 A single-crystal (C 6 H 5 C 2 H 4 NH 3 ) 2 PbI 4 device with a high detectivity (D*) of 1.89 × 10 15 Jones and an (NH 3 C 4 H 8 NH 3 )PbI 4 device with a low X-ray detection limit of 430 nGy air s −1 have been reported by Liu's group. 38,39 Our team has reported multiple cases of DJ-type HOIPs single-crystal photodetectors, such as (3AMPY)(EA)Pb 2 Br 7 (3AMPY = 3-(aminomethyl)pyridinium, EA = ethylammonium), 40 (3AMPY)(FA)Pb 2 I 7 (FA = formamidinium), 41 (3AMPY)(MA)Pb 2 Br 7 (MA = methylammonium), 42 and so on (details on the performance are listed in Table S1).…”

“…The flexibility of interlayer organic cations and the stability of inorganic components endow two-dimensional (2D) hybrid organic–inorganic perovskite (HOIP) semiconductors with versatility in composition and structure. − Among them, 2D Ruddlesden–Popper (RP) type and Dion–Jacobson (DJ) type HOIPs are widely used in photovoltaic field due to their high stability and strong performance adjustability. − Especially, the application of HOIPs in photodetection has also received increasing attention from multiple disciplines. − At present, 2D HOIPs are mainly used for photodetection in two forms: thin-film and single-crystalline. − For polycrystalline thin films, the internal grain boundaries and defects increase the scattering and recombination of photoinduced carriers, which reduces the carrier transmission efficiency and limits the performance of devices. Compared with polycrystalline thin films, single-crystalline materials have been proved to have the advantages of a low trap density and high mobility, which are considered ideal for constructing high-performance optoelectronic devices. − In this case, a series of 2D HOIPs single crystals are used for broadband photodetection.…”

Broad-Band Emission Switch in Room Temperature Stable Hybrid Perovskite Polymorphs

“…α-(C3aH) 2 PbBr 4 has recently been reported to crystallize in the P 2 1 / n monoclinic space group with two crystallographically independent organic molecules and one independent Pb 2+ ion . The new β-(C3aH) 2 PbBr 4 crystallizes in the monoclinic P 2 1 / c space group, the asymmetric unit containing one molecule and one Pb 2+ ion located on a −1 site (Table ).…”