Aromatic Spacer Research Articles

Engineering Spacer Conjugation for Efficient and Stable 2D/3D Perovskite Solar Cells and Modules

Incorporating 2D perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky‐cation‐based 2D structures often exhibit poor charge transport and are prone to formation of charge‐extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with enhanced molecular conjugation. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency of up to 25.3% in a 0.16‐cm2 single cell and 21.0% in a 24.8‐cm2 module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA‐based devices retained over 90% of their initial efficiency after 2000 hours at 25 ℃ and 80% relative humidity, or 1000 hours at 85 ℃ and 85% humidity, or 3000 hours of operation under continuous 1‐Sun illumination at 40 ℃, showcasing their enhanced stability compared to previously reported 2D/3D PSCs.

Engineering Spacer Conjugation for Efficient and Stable 2D/3D Perovskite Solar Cells and Modules.

Incorporating 2D perovskite in 3D perovskite absorber holds great potential to improve the stability and efficiency of perovskite solar cells (PSCs). However, the bulky-cation-based 2D structures often exhibit poor charge transport and are prone to formation of charge-extraction barrier that impedes efficient device operation. We address these issues by introducing aromatic spacers with enhanced molecular conjugation. Among our tested aromatic spacers, the pyrenylbutanamine (PyBA) spacer was shown to endow 2D perovskites with superior charge transport properties and efficient charge extraction from the bulk perovskite in 2D/3D PSCs, due to the highest degree of conjugation. As a result, we achieved a power conversion efficiency of up to 25.3% in a 0.16-cm2 single cell and 21.0% in a 24.8-cm2 module. Moreover, the incorporated PyBA substantially raised the resistance of 2D/3D PSCs against moisture and ion migration, resulting in enhanced environmental, thermal, and operational stability. Notably, the PyBA-based devices retained over 90% of their initial efficiency after 2000 hours at 25 ℃ and 80% relative humidity, or 1000 hours at 85 ℃ and 85% humidity, or 3000 hours of operation under continuous 1-Sun illumination at 40 ℃, showcasing their enhanced stability compared to previously reported 2D/3D PSCs.

Positional Isomerism of Aromatic Heterocyclic Spacer Cations in Two-Dimensional Dion-Jacobson Hybrid Perovskites.

Ligand engineering of aromatic heterocyclic cations in two-dimensional (2D) Dion-Jacobson (DJ) perovskites has been widely explored in recent years. In this study, how the positional isomers of aromatic heterocyclic cations tune the lattice of 2D perovskites, thereby influencing the transport and recombination dynamics of charge carriers, has been investigated through nonadiabatic molecular dynamics simulations. We demonstrate that the meta-substituted 3-(aminomethyl)pyridinium (3AMPY) cations greatly reduce the strength of electron-vibration coupling since the strong hydrogen-bonding network introduced by the changes in the arrangement of spacer cations significantly suppresses the structural thermal fluctuations. Compared to the para-substituted 4-(aminomethyl)pyridinium (4AMPY) cation, using the asymmetric 3AMPY as a spacer cation can achieve improved in-plane transport performance, enhanced thermal stability, and suppressed charge carrier recombination through weakening electron-vibration interactions. Our results explain the observed lifetime difference between the two types of DJ-phase perovskites in experiments and provide new guidance for optimizing the performance of perovskite devices.

Polar Alternating Cations Intercalated Hybrid Perovskite with Iodine‐Substituted Spacers Toward Efficient Passive X‐Ray Detection

Abstract2D hybrid perovskites, with their high X‐ray absorption and extended carrier transport, present excellent promise for efficient direct X‐ray detection. However, most of the current devices require external bias voltage, which results in the need for significant energy consumption and severe ion migration, therefore, it is urgent to develop new types of materials for achieving efficient passive X‐ray detection. Herein, two novel chiral polar alternating cations intercalation (ACI)‐type hybrid perovskite materials, named (R/S‐PPA)(IEA)PbBr4 (1‐R/S, (R/S)‐PPA = R/S‐1‐phenylpropylamine; IEA = iodoethylamine), are constructed by integrating the chiral aromatic spacer R/S‐PPA and the iodine‐substituted spacer IEA. Various intermolecular interactions, such as I···I, C─H···I, π···π interactions, are introduced due to the introduction of I‐substituted chain amines, which effectively suppresses ion migration and thus lead to improved operational stability. The device constructed along the polar axis displays superior X‐ray detection performance, such as relatively high sensitivity and an ultra‐low limit of detection (LoD) of 3.0 nGy s−1, making it the first chiral ACI‐type perovskite material for realizing efficient passive X‐ray detection. Furthermore, 1‐R also presents low dark current drift and exceptional irradiation stability. This work provides new thought for using novel ACI‐type polar perovskite for high‐performance passive direct X‐ray detection.

A Novel Thiazole‐Core Spacer Based Dion–Jacobson Perovskite with Type II Quantum Well Structure for Efficient Photovoltaics

Abstract2D Dion–Jacobson (DJ) perovskites show structural stability and tunability and are regarded as promising photovoltaic materials. The spacer cations play an important impact on exciton separation and charge transport of 2D perovskites. Herein, a novel spacer with thiazole as core, 2‐thiazolemethanammonium (AMT), owning characters of small molecular size, delocalized π‐electrons, and strong electron‐withdrawing ability, is introduced to construct 2D DJ perovskites. Owing to the strong orbital coupling between AMT spacer and inorganic layers, the AMT‐based perovskite exhibits type II quantum well structure, which is favorable for exciton separation. On contrary, such interaction does not appear in the DJ perovskite when aliphatic propyldiammonium (PDA), with a similar length, is used as spacer. The AMT spacer can also induce better crystallinity, resulting in reduced defect density and improved charge transport ability. The optimized device based on (AMT)MA3Pb4I13 exhibits a power conversion efficiency (PCE) of 19.69%, which is a record for 2D DJ perovskite solar cells (PSCs) (n ≤ 4). This work provides deep understanding of the impact of aromatic spacer on the electronic structure of 2D DJ perovskites and the corresponding photovoltaic performance and provides a new opportunity toward highly efficient and stable PSCs.

Bismuth (Bi3+) based lead-free halide perovskitoid for light driven applications: A potential low-toxic alternative for lead (Pb2+)

Bismuth-based perovskite-like materials are recognised as feasible optoelectronic alternatives to lead-based perovskites. High toxicity and limited environmental stability of Pb-based perovskite are the principal hurdles for their practical use, whereas Bismuth (Bi3+) based materials exhibit relatively low toxicity. In this study, we fabricated (FPEA)BiI4 (FPEA = Fluorophenylethyl amine, as a hydrophobic aromatic spacer) and explored its compatibility in the field of photocatalysis and solar cells. UV–Vis, photoluminescence (PL) and time-correlated single photon counting (TCSPC) techniques were used to understand the optoelectronic properties of the material. These fabricated thin films were used towards toxic MBT remediation. Solar cells (in n-i-p configuration) were also fabricated using (FPEA)BiI4 and their photo conversion efficiency (PCE) was tested under AM1.5 illumination.

Dion-Jacobson Type Lead-Free Double Perovskite with Ultra-Narrow Aromatic Interlayer Spacing for Highly Sensitive and Stable X-ray Detection.

The low-toxic and environmentally friendly 2D lead-free perovskite has made significant progress in the exploration of "green" X-ray detectors. However, the gap in detection performance between them and their lead-based analogues remains a matter of concern that cannot be ignored. To reduce this gap, shortening the interlayer spacing to accelerate the migration and collection of X-ray carriers is a promising strategy. Herein, a Dion-Jacobson (DJ) lead-free double perovskite (4-AP)2 AgBiBr8 (1, 4-AP = 4-amidinopyridine) with an ultra-narrow interlayer spacing of 3.0Å, is constructed by utilizing π-conjugated aromatic spacers. Strikingly, the subsequent enhanced carrier transport and increased crystal density lead to X-ray detectors based on bulk single crystals of 1 with a high sensitivity of 1117.3µCGy-1 cm-2 , superior to the vast majority of similar double perovskites. In particular, the tight connection of the inorganic layers by the divalent cations enhances structural rigidity and stability, further endowing 1 detector with ultralow dark current drift (3.06×10-8 nAcm-1 s-1 V-1 , 80V), excellent multiple cycles switching X-ray irradiation stability, as well as long-term environmental stability (maintains over 94% photoresponse after 90 days). This work brings lead-free double perovskites one step closer to realizing efficient practical green applications.

Bilayered Dion-Jacobson lead-iodine hybrid perovskite with aromatic spacer for broadband photodetection

Bilayered Dion-Jacobson lead-iodine hybrid perovskite with aromatic spacer for broadband photodetection

Mixed ionic-electronic conduction in Ruddlesden–Popper and Dion–Jacobson layered hybrid perovskites with aromatic organic spacers

Mixed ionic-electronic conduction in Ruddlesden–Popper and Dion–Jacobson layered hybrid perovskites with aromatic organic spacers

Dion–Jacobson Phase Perovskite Crystal Assembled by π‐Conjugated Aromatic Spacer for X‐Ray Detectors with an Ultralow Detection Limit

Abstract2D Dion–Jacobson (DJ) perovskites recently have attracted extensive attention for X‐ray detection owing to their structural rigidity and environmental stability. The chemical incorporation of π‐conjugation aromatic spacing cations into DJ phase perovskites will increase the rigidity of cation and electron cloud density between adjacent inorganic slabs, thus facilitating structural rigidity and charge transport. However, it is still a challenge to synthesize high‐quality single crystals of DJ phase perovskite with aromatic spacers for detecting X‐ray applications. Here, a new DJ phase perovskite by introducing π‐conjugated aromatic cation spacer, (4ABA)PbI4 (1, 4ABA = 4‐aminobenzylamine), eliminating the van der Waals gap is designed. High‐quality single crystals of 1 are grown via the facile solution method, exhibiting high resistivity (1.97 × 1011 Ω cm), low trap density (3.36 × 109 cm−3), and large carrier mobility‐lifetime product (1.03 × 10−3 cm2 V−1) under X‐ray illumination. Such remarkable physical characteristics endow single crystal 1 detector with high‐performance X‐ray detection including a high sensitivity of 572 µC Gyair−1cm−2, an ultralow detection limit of 7.50 nGyair s−1 and exceptional radiation stability. The X‐ray detection limit of 1 is over 700 times lower than that of routine medical diagnosis (5500 nGyair s−1), demonstrating potential applications in medical examination.

Impact of bridge heterology on functional parameters of ELISA for 17α-methyltestosterone

In this study, we have developed bridge heterologous ELISA for the detection of 17α- Methyltestosterone by incorporating aromatic spacers between 17α-Methyltestosterone-3-Carboxymethyloxime and Horseradish peroxidase label through N-hydroxysuccinimide mediated carbodiimide reaction method. The immunogen 17α-Methyltestosterone-3-Carboxymethyloxime-Bovine serum albumin used to generate the antibody was also prepared by the N-hydroxysuccinimide mediated carbodiimide reaction without using any spacer. We have studied the impact of bridge/aromatic spacers on functional parameters i.e. sensitivity, affinity and ED50 of the bridge heterologous assay and compared it with homologous assay. The five combinations of bridge heterologous assay using 17α-Methyl testosterone-3-CMO-BSA antiserum and 17α-MT-3-CMO-4,4’-Diaminodiphenyl sulphide-HRP, 17α MT-3-CMO-4,4’-Oxydianiline-HRP, 17α-MT-3-CMO-Benzidine-HRP, 17α- MT-3-CMO-p-Phenylenediamine-HRP and 17α-MT-3-CMO-Dapson-HRP enzyme conjugates were evaluated. Out of these five combinations, the combination 17α-MT-3-CMO-BSA with 17α-MT-3-CMO-Benzidine-HRP showed the best results. Sensitivity, affinity and ED50 were improved and found to be 0.02 ng/mL, 0.086 × 10−8 L/mol and 2.95 ng/mL than homologous assay where Sensitivity, affinity and ED50 were 0.11 ng/mL, 0.02 × 10−8 L/mol and 5.78 ng/mL respectively. The cross-reactivity for this bridge heterologous assay combination was seen with only 4 steroids (6-hydrotestosterone- 6%, Testosterone-5.14%, Danazol-0.9% and Nandrolone-0.85%) instead of eight steroids (6-hydrotestosterone-43.75%, Testosterone-38.3%, Danazol-25.14%, Androstenediol-19.16%, Nandrolone-19%, Metandienone-5%, Androstenedione-3.52%, and 17α dimethyltestosterone-2%) as in homologous assay out of 59 structurally related steroids.Thus, the results of this study conclude that the incorporation of aromatic spacer (bridge) in enzyme conjugate has a crucial role in improving sensitivity, specificity, ED50 and affinity of the developed assay. The assay was then studied for parameters such as recovery (97.4%–108.6%), precision (Inter and Intra-assay coefficient of variation <10%), correlation coefficient (R2 = 0.96) by comparing with the commercial kit and validated by measuring levels of 17α- methyltestosterone in rat serum after administering them.

Improving Crystallinity and Out-of-Plane Orientation in Quasi-2D Ruddlesden-Popper Perovskite by Fluorinated Organic Salt for Light-Emitting Diodes.

Fluoro-substituted aromatic alkylammonium spacer cations are found effective to improve the performance of quasi-2D perovskite light-emitting diodes (PeLEDs). The fluorine substitution is generally attributed to the defect passivation, quantum well width control, and energy level adjustments. However, the substituted cations can also affect the crystallization process but is not thoroughly studied. Herein, a comparison study is carried out using bare PEA cation and three different fluoro-substituted PEA (x-F-PEA, x = o, ortho; m, meta; p, para) cations to investigate the impacts of different substitution sites on the perovskite crystallization and orientations. By using GIWAXS, p-F-PEA cation is found to induce the strongest preferential out-of-plane orientations with the best crystallinity in quasi-2D perovskite. Using dynamic light scattering (DLS) methods, larger colloidal particles (630 nm) are revealed in p-F-PEA precursor solutions than the PEA cations (350 nm). The larger particles can accelerate the crystallization process and induce out-of-plane orientation from increased dipole-dipole interaction. The transient absorption measurement confirms longer radiative recombination lifetime, proving beneficial effect of p-F-PEA cation. As a result, the fabricated p-F-PEA-based PeLEDs achieved the highest EQE of 15.2%, which is higher than those of PEA- (8.8%), o-F-PEA- (4.3%), and m-F-PEA-based (10.3%) PeLEDs.

Stacking Arrangement and Orientation of Aromatic Cations Tune Bandgap and Charge Transport of 2D Organic-Inorganic Hybrid Perovskites.

Chemical modifications on aromatic spacers of 2D perovskites have been demonstrated to be an effective strategy to simultaneously improve optoelectronic properties and stability. However, its underlying mechanism is poorly understood. By using 2D phenyl-based perovskites ([C6 H5 (CH2 )m NH3 ]2 PbI4 ) as models, the authors have revealed how the chemical nature of aromatic cations tunes the bandgap and charge transport of 2D perovskites by utilizing sum-frequency generation vibrational spectroscopy to determine the stacking arrangement and orientation of aromatic cations. It is found that the antiparallel slip-stack arrangement of phenyl rings between adjacent layers induces an indirect band gap, resulting in anomalous carrier dynamics. Incorporation of the CH2 moiety causes stacking rearrangement of the phenyl ring and thus promotes an indirect to direct bandgap transition. In direct-bandgap perovskites, higher carrier mobility correlates with a larger orientation angle of the phenyl ring. Further optimizing the orientation angle by introducing a para-substituted element in a phenyl ring, higher carrier mobility is obtained. This work highlights the importance of leveraging stacking arrangement and orientation of the aromatic cations to tune the photophysical properties, which opens up an avenue for advancing high-performance 2D perovskites optoelectronics via molecular engineering.

“Functional connector” strategy on tunable organo-vermiculites: The superb adsorption towards Congo Red

With the increasingly worldwide concentration of environmental pollution, exploiting cost-effective adsorbents has been a research hotspot. Here we introduce novel “functional connector” amide-containing gemini surfactants (LDAB, LDAPP, LDAMP and LDABP) and apply to modify Na-vermiculite (Na-Vt) for Congo red (CR) removal. Chain amide as the functional connector in the modifier, increases 6.9 times of CR uptake than traditional organo-Vts, which is further enhanced by tunning the functional group of modifier spacers. Superb uptake of CR on organo-Vts reaches 1214.05, 1375.47 and 1449.80 mg/g, and the removal efficiencies achieve 80.94%, 91.70% and 96.65% on LDAB-Vt, LDAPP-Vt and LDAMP-Vt, respectively. Notably, the maximum experimental adsorption capacity of LDAPP-Vt is 1759.64 mg/g. These experimental values are among the highest reported CR adsorbents. A combination experimental and theoretical analysis is conducted to unveil the structure-adsorptivity relationship: (i) Adsorptivity enhancement of organo-Vts is more effectively by regulating functional chains than the functional spacer. (ii) para-substituted aromatic spacers own the best adsorptive configuration and strongest stability for π-π interaction. (iii) π-π interaction provided by isolated aromatic ring is stronger than biphenyl, whose steric hindrance depresses the adsorptivity. Results in this study not only explain a new “functional connector” strategy to Vt-based adsorbents, but also provide a practical designing strategy for organic adsorbents characterized with high uptake capacity.

Fast and Tunable Phosphorescence from Organic Ionic Crystals

AbstractCrystalline diphosphonium iodides [MeR2P‐spacer‐R2Me]I with phenylene (1, 2), naphthalene (3, 4), biphenyl (5) and anthracene (6) as aromatic spacers, are photoemissive under ambient conditions. The emission colors (λem values from 550 to 880 nm) and intensities (Φem reaching 0.75) are defined by the composition and substitution geometry of the central conjugated chromophore motif, and the anion‐π interactions. Time‐resolved and variable‐temperature luminescence studies suggest phosphorescence for all the titled compounds, which demonstrate observed lifetimes of 0.46–92.23 μs at 297 K. Radiative rate constants kr as high as 2.8×105 s−1 deduced for salts 1–3 were assigned to strong spin‐orbit coupling enhanced by an external heavy atom effect arising from the anion‐π charge‐transfer character of the triplet excited state. These rates of anomalously fast metal‐free phosphorescence are comparable to those of transition metal complexes and organic luminophores that utilize triplet excitons via a thermally activated delayed fluorescence mechanism, making such ionic luminophores a new paradigm for the design of photofunctional and responsive molecular materials.

Fast and Tunable Phosphorescence from Organic Ionic Crystals.

Crystalline diphosphonium iodides [MeR2P-spacer-R2Me]I with phenylene (1, 2), naphthalene (3, 4), biphenyl (5) and anthracene (6) as aromatic spacers, are photoemissive under ambient conditions. The emission colors (λem values from 550 to 880 nm) and intensities (Φem reaching 0.75) are defined by the composition and substitution geometry of the central conjugated chromophore motif, and the anion-π interactions. Time-resolved and variable-temperature luminescence studies suggest phosphorescence for all the titled compounds, which demonstrate observed lifetimes of 0.46-92.23 μs at 297 K. Radiative rate constants kr as high as 2.8 × 105 s-1 deduced for salts 1-3 were assigned to strong spin-orbit coupling enhanced by an external heavy atom effect arising from the anion-π charge-transfer character of the triplet excited state. These rates of anomalously fast metal-free phosphorescence are comparable to those of transition metal complexes and organic luminophores that utilize triplet excitons via a thermally activated delayed fluorescence mechanism, making such ionic luminophores a new paradigm for the design of photofunctional and responsive molecular materials.

Improving Out-of-Plane Charge Mobility and Phase Stability of Dion-Jacobson Lead-Free Perovskites via Intercalating π-Conjugated Aromatic Spacers.

The layered quasi-2D perovskites are recognized as one of the effective strategies to resolve the big problem of intrinsic phase instability of the perovskites. However, in such configurations, their performance is fundamentally limited due to the correspondingly weakened out-of-plane charge mobility. Herein, the π-conjugated p-phenylenediamine (PPDA) is introduced as organic ligand ions for rationally designing lead-free and tin-based 2D perovskites with the aid of theoretical computation. It is evidenced that both out-of-plane charge transport capacity and stability can be significantly enhanced within as-established quasi-2D Dion-Jacobson (DJ) (PPDA)Csn -1 Snn I3 n +1 perovskites. The obviously increased electrical conductivity and reduced carrier effective masses are attributed to the enhanced interlayer interactions, limited structural distortions of diamine cations, as well as improved orbital coupling between Sn2+ and I- ions of (PPDA)Csn -1 Snn I3 n +1 perovskites. Accordingly, by dimension engineering of the inorganic layer (n), the bandgap (Eg ) of quasi-2D perovskites can be linearly tailored toward the suitable Eg (1.387eV) with optimal photoelectric conversion efficiency (PCE) of 18.52%, representing their great potential toward promising applications in advanced solar cells.

Improving Properties of Podophyllic Aldehyde-Derived Cyclolignans: Design, Synthesis and Evaluation of Novel Lignohydroquinones, Dual-Selective Hybrids against Colorectal Cancer Cells

New lignohydroquinone conjugates (L-HQs) were designed and synthesized using the hybridization strategy, and evaluated as cytotoxics against several cancer cell lines. The L-HQs were obtained from the natural product podophyllotoxin and some semisynthetic terpenylnaphthohydroquinones, prepared from natural terpenoids. Both entities of the conjugates were connected through different aliphatic or aromatic linkers. Among the evaluated hybrids, the L-HQ with the aromatic spacer clearly displayed the in vitro dual cytotoxic effect derived from each starting component, retaining the selectivity and showing a high cytotoxicity at short (24 h) and long (72 h) incubation times (4.12 and 0.0450 µM, respectively) against colorectal cancer cells. In addition, the cell cycle blockade observed by flow cytometry studies, molecular dynamics, and tubulin interaction studies demonstrated the interest of this kind of hybrids, which docked adequately into the colchicine binding site of tubulin despite their large size. These results prove the validity of the hybridization strategy and encourage further research on non-lactonic cyclolignans.

Air and Moisture Stable para- and ortho-Quinodimethane Derivatives Derived from bis-N-Heterocyclic Olefins.

Herein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of bis-N-heterocyclic olefins linked by different π-conjugated aromatic spacers. In case of para- and ortho-phenylene bridge, we obtained air and moisture stable diimidazolium para- and ortho-quinodimethane derivatives. Analogues of the para-phenylene spacer such as tetrafluoro-p-phenylene and p-anthracene also led to the corresponding air and moisture stable quinodimethane derivatives. This emphasizes the influence of imidazolium substituents which facilitate the air and moisture stability of the quinodimethane derivatives. Differences were observed for the electron transfer processes: two one-electron vs one two-electron redox transitions between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes depending on the employed π-conjugated aromatic spacer. The formation of the π-conjugated radical-cations, transient redox intermediates between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes, was addressed by an EPR investigation.

Acquiring Bulk Anomalous Photovoltaic Effect in Single Crystals of a Lead-Free Double Perovskite with Aromatic and Alkali Mixed-Cations.

The bulk anomalous photovoltaic (BAPV) effect of acentric materials refers to a distinct concept from traditional semiconductor-based devices, of which the above-bandgap photovoltage hints at a promise for solar-energy conversion. However, it is still a challenge to exploit new BAPV-active systems due to the lacking of knowledge on the structural origin of this concept. BAPV effects in single crystals of a 2D lead-free double perovskite, (BBA)2 CsAgBiBr7 (1, BBA = 4-bromobenzylammonium), tailored by mixing aromatic and alkali cations in the confined architecture to form electric polarization are acquired here. Strikingly, BAPV effects manifested by above-bandgap photovoltage (VOC ) show unique attributes of directional anisotropy and positive dependence on electrode spacing. The driving source stems from orientations of the polar aromatic spacer and Cs+ ion drift, being different from the known built-in asymmetry photovoltaic heterojunctions. As the first demonstration of the BAPV effect in the double perovskites, the results will enrich the family of environmentally green BAPV-active candidates and further facilitate their new optoelectronic application.