Thiophene Cation Intercalation to Improve Band‐Edge Integrity in Reduced‐Dimensional Perovskites

Abstract

The insertion of large organic cations in metal halide perovskites with reduced-dimensional (RD) crystal structures increases crystal formation energy and regulates the growth orientation of the inorganic domains.H owever,t he power conversion performance is curtailed by the insulating nature of the bulky cations.N ow as eries of RD perovskites with 2thiophenmethylammonium (TMA) as the intercalating cation are investigated. Compared with traditional ligands,T MA demonstrates improved electron transfer in the inorganic framework. TMA modifies the near-band-edge integrity of the RD perovskite,i mproving hole transport. Ap ower conversion efficiency of 19 %i sa chieved, the highest to date for TMA-based RD perovskite photovoltaics;t hese TMA devices providea12 %r elative increase in PCE compared to control RD perovskite devices that use PEA as the intercalating ligand, ar esult of the improved charge transfer from the inorganic layer to the organic ligands.

Charge‐Carrier Transport in Quasi‐2D Ruddlesden–Popper Perovskite Solar Cells

“…They found that compared to other cations, thiophene cations have more near band-edge states due to the delocalization effect caused by the strongly polarized sulfur atom, which significantly facilitates chargecarrier migration (Figure 2d), resulting in a PCE of 19% for TMA-based PSCs. [30] Interestingly, Liu et al proposed the use of ionic liquid 1-butyl-3-methylimidazolium iodide as the spacer, and through the hydrogen bond with the inorganic layer (Figure 2e), the imidazole rings of the two layers were arranged coplanarly, which dramatically reduced the interlayer spacing and weakened the quantum confinement, leading to a smooth charge through the organic ammonium molecules. [31] It can be concluded that introducing aromatic spacer cations to produce intermolecular or intramolecular interactions can improve the energy arrangement with the inorganic layer and effectively increase the out-of-plane conductivity, thereby greatly promoting carrier transport.…”

Regulating the phase stability and bandgap of quasi-2D Dion–Jacobson CsSnI3 perovskite via intercalating organic cations

“…3f). 29,56,57 The variation tendency of the bandgaps ( E g ) of (ThDMA)Cs n −1 Sn n I 3 n +1 perovskites calculated by the HSE06 functional generally resembled that by the PBE. The E g of quasi-2D (ThDMA)Cs n −1 Sn n I 3 n +1 perovskites decreased with the n increasing and closely depended on its dimensionality n , which can be efficiently engineered.…”

Reversible Emission Tunability from 2D‐Layered Perovskites with Conjugated Organic Cations

“…Upon excitation with a laser at 375 nm wavelength, the TEA samples display deep‐blue emission with a double‐peak structure (414–425 nm) that is characteristic of ensembles of 2D HLPs. [ 10,25,28 ] This blue band edge emission is accompanied by weak broadband emission in the green–red spectral range that is more pronounced in the 0.6 mmol TEA sample (as shown in the inset in Figure 2c). The TMA samples also show the blue band edge emission, although here the double peak feature is less resolved.…”

“…From the experimental powder XRD patterns in Figure 1c‐d, we observe periodic reflections from which the interdistances, d , between Pb–Br layers were estimated as 15.75 and 14.49 Å for TEA‐ and TMA‐based crystals, respectively, regardless of the cation content. We used as a reference the reported crystallographic data for (TMA) 2 PbI 4 [ 25 ] after substituting I − halide anions for Br − ones in the structure (Figure S2, Supporting Information) and refining the cell parameters using CrystalDiffract v. 6.9.0 software. [ 27 ]…”

“…These cations are part of the π ‐conjugated molecule family, for which significantly improved charge mobility in 2D HLP‐based solar cells has been recently demonstrated. [ 25 ] Furthermore, we show how such thiophene‐based 2D HLPs can be easily doped to generate dual emission from a single structure. Given the importance of these materials for light‐emitting applications, the strategies to modulate their photoluminescence (PL) as desired are highly appealing, in particular, because these properties come together with enhanced organic–inorganic charge transfer features that are inherent to thiophenes.…”