Dion-Jacobson Perovskites Research Articles

Highly Efficient and Stable Dion-Jacobson Perovskite Solar Cells Enabled by Extended π-Conjugation of Organic Spacer.

2D Dion-Jacobson (DJ) perovskites have become an emerging photovoltaic material with excellent structure and environmental stability due to their lacking van der Waals gaps relative to 2D Ruddlesden-Popper perovskites. Here, a fused-thiophene-based spacer, namely TTDMAI, is successfully developed for 2D DJ perovskite solar cells. It is found that the DJ perovskite using TTDMA spacer with extended π-conjugation length exhibits high film quality, large crystal size and preferred crystal vertical orientation induced by the large crystal nuclei in precursor solution, resulting in lower trap density, reduced exciton binding energy and oriented charge transport. As a result, the optimized 2D DJ perovskite device based on TTDMA (nominal n= 4) delivers a champion PCE up to 18.82%. Importantly, the unencapsulated device based on TTDMA can sustain average 99% of their original efficiency after being stored in N2 for 4400 h (over 6 months). Moreover, light, thermal, environmental and operational stabilities are also significantly improved in comparison with their 3D counterparts.

Room Temperature Fabrication of Stable, Strongly Luminescent Dion-Jacobson Tin Bromide Perovskite Microcrystals Achieved through Use of Primary Alcohols.

Lead-free two-dimensional metal halide perovskites have recently emerged as promising light-emitting materials due to their improved stability and attractive optical properties. Herein, a facile room temperature wet milling method has been developed to make Dion–Jacobson (DJ) phase ODASnBr4 perovskite microcrystals, whose crystallization was accomplished via the aid of introduced primary alcohols: ethanol, butanol, pentanol, and hexanol. Due to the strong intermolecular hydrogen bonding, the use of ethanol promoted the formation of non-doped ODASnBr4 microcrystals, with an emission peaked at 599 nm and a high photoluminescence quantum yield (PL QY) of 81%. By introducing other primary alcohols with weaker intermolecular hydrogen bonding such as butanol, pentanol, and hexanol, [SnBr6]4− octahedral slabs of the DJ perovskite microcrystals experienced various degrees of expansion while forming O–H…Br hydrogen bonds. This resulted in the emission spectra of these alcohol-doped microcrystals to be adjusted in the range from 572 to 601 nm, while keeping the PL QY high, at around 89%. Our synthetic strategy provides a viable pathway towards strongly emitting lead-free DJ perovskite microcrystals with an improved stability.

Superior Performance and Stability of 2D Dion–Jacobson Halide Perovskite Photodetectors Operated under Harsh Conditions without Encapsulation

AbstractThe practical utilization of electronic and optoelectronic materials such as perovskites not only relies on their good device performance and moisture stability but also requires stability under other operating conditions. Herein, the operational stability of the Dion–Jacobson perovskite (DJP) photodetector under different harsh conditions is carefully studied and compared with that of its widely studied counterpart, i.e., the Ruddlesden–Popper perovskite (RPP) photodetector. The DJP‐based photodetector can maintain its responsivity after storage in humid environments for two months and can ensure stable operation without any photocurrent degradation under continuous light illumination for 20 000 s. Moreover, the DJP film does not exhibit any changes in its absorbance spectrum and surface morphology when it is heated at 100 °C for 18 h, and the film is hardly affected by high‐energy electron beam irradiation. In addition, the mechanical stability of the DJP film is also found to be superior based on the cyclic bending measurements of the fabricated flexible photodetectors. The excellent performance and stability of the DJP‐based photodetector are found to be the result of the elimination of weak van der Waals bonds among the octahedral PbI4 layers of DJP films, which is typically observed in RPP films.

Observation of Defect Luminescence in 2D Dion–Jacobson Perovskites

AbstractThe luminescent property of 2D perovskite materials promotes their applications in light emitting diodes, phosphor powders, and scintillators. Recently, an interesting extrinsic low‐energy broadband luminescence is hotly investigated. However, the understanding of such emissions is still at the early stage. In this study, based on a modified solvent evaporation method, centimeter‐size (BDA)PbI4 (BDA = NH3C4H8NH32+) single crystals are grown which, besides the band–band emission, show a large Stokes‐shifted broadband luminescence. We find such emission can be effectively excited by sub‐gap photons and conclude defects‐induced shallow traps are the corresponding luminescence centers. Density functional theory (DFT) calculations indicate that in‐plane iodine vacancies can introduce shallow electron traps in the band gap and give rise to the broadband emission.

Suppressed Phase Segregation in High‐Humidity‐Processed Dion–Jacobson Perovskite Solar Cells Toward High Efficiency and Stability

The Dion–Jacobson (DJ) perovskites solar cells (PSCs) demonstrate impressive humidity stability compared with 3D counterparts and have aroused extensive attention recently. However, it has not been investigated yet, how the humidity condition influences the photovoltaic performances. Herein, the effect of the humidity condition on the crystallization behavior, charge dynamics, photovoltaic and stability performances of BDAFAn‐1PbnI3n+1 DJ perovskite is systematically investigated. Humidity‐assisted annealing process can lead to reduced trap concentration and fast charge transfer process between different‐n DJ phases. The BDAFA5Pb6I19 PSC with the assistance of moisture achieves an efficiency as high as 17.17%, which is the highest value ever reported for methylammonium‐free DJ PSCs. In addition, the humidity‐, thermal‐, and photo‐stability properties of the DJ film and devices are significantly boosted. Further, first‐principles calculation indicates that water molecules occupy the iodide vacancies through a strong bonding with Pb ions during the crystallization process under humidity and increase the decomposition energy of the DJ phase, which corresponds to the improved photoelectronic and stability properties. These results show that humidity‐assisted deposition of 2D/3D multidimensional perovskite can be further explored to reduce the high demand of the production environment and enhance the performances.

M-Phenylenediammonium as a New Spacer for Dion-Jacobson Two-Dimensional Perovskites.

Two-dimensional (2D) halide perovskites have several distinct structural classes and exhibit great tunability, stability, and high potential for photovoltaic applications. Here, we report a new series of hybrid 2D perovskites in the Dion-Jacobson (DJ) class based on aromatic m-phenylenediammonium (mPDA) dications. The crystal structures of the DJ perovskite materials (mPDA)MAn-1PbnI3n+1 (n = 1-3) were solved and refined using single-crystal X-ray crystallography. The results indicate a short I···I interlayer distance of 4.00-4.04 Å for the (mPDA)MAn-1PbnI3n+1 (n = 2 and 3) structures, which is the shortest among DJ perovskites. However, Pb-I-Pb angles are as small as 158-160°, reflecting the large distortion of the inorganic framework, which results in larger band gaps for these materials than those in other DJ analogues. Density functional theory calculations suggest appreciable dispersion in the stacking direction, unlike the band structures of the Ruddlesden-Popper phases, which exhibit flat bands along the stacking direction. This is a consequence of the short interlayer I···I distances that can lead to interlayer electronic coupling across the layers. The solution-deposited films (nominal (mPDA)MAn-1PbnI3n+1 compositions of n = 1-6) reveal improved surface coverage with increasing nominal n value with the higher n films being composed of a mixture of n = 1 and bulk three-dimensional MAPbI3 perovskites. The films made from solutions of these materials behave differently from those of other 2D iodide perovskites, and their solar cells have a mixture of n = 1 DJ and MAPbI3 as light-absorbing semiconductors.

Multiple-Noncovalent-Interaction-Stabilized Layered Dion-Jacobson Perovskite for Efficient Solar Cells.

Two-dimensional Dion-Jacobson (DJ) perovskites have shown improved structure stability in comparison with Ruddlesden-Popper (RP) perovskites. However, the mechanism behind the improved stability is still largely unexplored. Here a multifluorinated aromatic spacer, namely, 4F-PhDMA, has been successfully developed for 2D DJ perovskites. It is found that the 2D DJ perovskite with a 4F-PhDMA spacer exhibits a high dissociation energy due to the multiple noncovalent interactions. The optimized 2D DJ device based on the 4F-PhDMA spacer (n = 4) exhibits a champion efficiency of 16.62% with much improved light and thermal stability. This efficiency is much higher than that of the control device using an unfluorinated spacer (n = 4, PCE = 10.11%) and is among the highest efficiencies in aromatic-spacer-based 2D DJ perovskite solar cells (PSCs). Our work highlights the importance of incorporating multiple noncovalent interactions in the 2D DJ perovskite by employing a multifluorinated aromatic spacer to achieve DJ PSCs with both high efficiency and high stability.

Thermally Assisted Rashba Splitting and Circular Photogalvanic Effect in Aqueously Synthesized 2D Dion-Jacobson Perovskite Crystals.

Recently, a two-dimensional Dion-Jacobson (DJ) perovskite (AMP)PbI4 (AMP = 4-(aminomethyl)piperidinium) is emerging with remarkable Rashba effect and ferroelectricity. However, the origin of the giant Rashba splitting remains elusive and the current synthetic strategy via slow cooling is time- and power-consuming, hindering its future applications. Here, we report on an economical aqueous method to obtain (AMP)PbI4 crystals and clarify the origin of the giant Rashba effect by temperature- and polarization-dependent photoluminescence (PL) spectroscopy. The strong temperature-dependent PL helicity indicates the thermally assisted structural distortion as the main origin of the Rashba effect, suggesting that valley polarization still preserves at high temperatures. The Rashba effect was further confirmed by the circular photogalvanic effect near the indirect bandgap. Our study not only optimizes the synthetic strategies of this DJ perovskite but also sheds light on its potential applications in room/high-temperature spintronics and valleytronics.

Enhanced Electrochemical Stability by Alkyldiammonium in Dion–Jacobson Perovskite toward Ultrastable Light‐Emitting Diodes

AbstractThe electroluminescence efficiency of perovskite light‐emitting diodes (PeLEDs) has gained notable achievements, but the poor stability under electric stress severely impedes future practical use. Here, an alkyldiammonium 1,4‐butanediamine (BDA) is incorporated into perovskite emitting layer, which substantially optimizes electrochemical stability and minimizes interfacial deep traps under large external bias. The BDA‐PeLED shows a record operational half‐lifetime T50 of 189.4 h at a high current density of 100 mA cm−2 and 681 h under 50 mA cm−2. Additionally, the device maintains its original performance upon 2500 cycles of voltage scan and withstands 10 000 times of ON–OFF under a pulsed voltage of 2.5 V. Further degradation mechanism study reveals that the main origins of the instability property of PeLEDs without BDA are the generation of deep traps at the interfaces and the infiltration of anions into adjacent layers under long‐term electric stress. The significantly enhanced electrochemical stability suggests that alkyldiammonium cation incorporation can provide a direction to solve the instability issue of PeLEDs.

Strongly Luminescent Dion–Jacobson Tin Bromide Perovskite Microcrystals Induced by Molecular Proton Donors Chloroform and Dichloromethane

AbstractLead‐free 2D perovskites based on tin halide octahedron slabs with Dion–Jacobson (DJ) phases have drawn attention due to their improved stability; still, reports on light‐emitting DJ lead‐free perovskites are scarce. Herein, a room‐temperature ligand assisted re‐precipitation method is used to produce ODASnBr4 perovskite microcrystals (ODA denotes protonated 1,8‐octanediamine). After incorporating molecular dopants chloroform and dichloromethane, not only the crystallinity of the DJ perovskite phase improves, but their emission becomes much stronger due to the formation of hydrogen bonds between [SnBr6]4− octahedra and acidic CH proton donors. ODASnBr4 microcrystals doped with these molecules show a high photoluminescence quantum yield (PLQY) approaching 90%, and their emission remains stable under a continuous UV irradiation, with less than 10% loss in intensity over 6 h. Moreover, by tuning the pristine ODASnBr4 with various degrees of exposure to the molecular dopants, the maximum of their self‐trapped exciton emission can be fine‐tuned over a spectral range of 570–608 nm while maintaining high PLQYs of 83–88%. This provides a convenient way to adjust the spectral position of DJ perovskite emission without changing halides or A‐site spacers. Thus, stable and strongly emitting lead‐free DJ perovskite materials have been developed.

Enhancing the efficiency and stability of two-dimensional Dion–Jacobson perovskite solar cells using a fluorinated diammonium spacer

2,3,5,6-Tetrafluoro-1,4-benzenedimethanammonium is developed for 2D Dion–Jacobson perovskite solar cells which exhibit a significantly improved efficiency in comparison with that for the nonfluorinated diammonium-based counterparts.

Dion–Jacobson halide perovskites for photovoltaic and photodetection applications

This review focuses on recent progress involving the photovoltaic and photodetection properties of Dion–Jacobson perovskites and the enhanced stability of Dion–Jacobson perovskite solar cells.

Merged interface construction toward ultra-low Voc loss in inverted two-dimensional Dion–Jacobson perovskite solar cells with efficiency over 18%

By introducing a pretreatment combined with a merged annealing method, a dual-function PC61BM, which passivates interface defects and improves charge transport, was achieved to boost the PCE of 2D Dion–Jacobson perovskite solar cells to over 18%.

Suppressing the Excessive Solvated Phase for Dion–Jacobson Perovskites with Improved Crystallinity and Vertical Orientation

Dion–Jacobson (DJ)‐type quasi‐two‐dimensional perovskites exhibit improved stabilities than their 3D counterparts but meanwhile limited charge transport properties. Knowledge to manipulate the crystal orientation and crystallinity is the primary issue for DJ perovskite with high power conversion efficiencies (PCEs). Herein, the nucleation of DJ perovskite films is divided into three stages and the formation of PbI2–N,N‐dimethylformamide (DMF)‐based solvated phase (PDS) is highlighted as the initial stage. For the first time, it is demonstrated that regulating the amount of PDS precipitation in stage I by MACl additive is the key to ensure the downward growth of DJ perovskites with out‐of‐plane orientation and high crystallinity in stage III, which is valid for DJ perovskites with different bukly organic cations including p‐phenylenediamine (PPD), p‐xylylenediamine (PXD), and propane‐1,3‐diammonium (PDA). For (PXD)(MA)2Pb3I10‐based perovskite solar cells, the PDS engineering lead to a dramtically improved PCE from 1.2% to 15.6%. Moreover, based on temperature‐dependent ionic conductivity measurement, it is confirmed that the ion migration in DJ perovskite films is efficiently suppressed, despite the possible coexisting 3D perovskite phase. The unencapsulated PXD‐based DJ perovskite devices retain over 90% efficiencies after 700 h of continuous illumination or 1500 h of storage in glove box.

Narrow-Bandgap Mixed Lead/Tin-Based 2D Dion-Jacobson Perovskites Boost the Performance of Solar Cells.

The advent of the two-dimensional (2D) family of halide perovskites and their demonstration in 2D/three-dimensional (3D) hierarchical film structures broke new ground toward high device performance and good stability. The 2D Dion-Jacobson (DJ) phase halide perovskites are especially attractive in solar cells because of their superior charge transport properties. Here, we report on 2D DJ phase perovskites using a 3-(aminomethyl)piperidinium (3AMP) organic spacer for the fabrication of mixed Pb/Sn-based perovskites, exhibiting a narrow bandgap of 1.27 eV and a long carrier lifetime of 657.7 ns. Consequently, solar cells employing mixed 2D DJ 3AMP-based and 3D MA0.5FA0.5Pb0.5Sn0.5I3 (MA = methylammonium, FA = formamidinium) perovskite composites as light absorbers achieve enhanced efficiency and stability, giving a power conversion efficiency of 20.09% with a high open-circuit voltage of 0.88 V, a fill factor of 79.74%, and a short-circuit current density of 28.63 mA cm-2. The results provide an effective strategy to improve the performance of single-junction narrow-bandgap solar cells and, potentially, to give a highly efficient alternative to bottom solar cells in tandem devices.

Highly tunable properties in pressure-treated two-dimensional Dion–Jacobson perovskites

The application of pressure can achieve novel structures and exotic phenomena in condensed matters. However, such pressure-induced transformations are generally reversible and useless for engineering materials for ambient-environment applications. Here, we report comprehensive high-pressure investigations on a series of Dion-Jacobson (D-J) perovskites A'A n-1Pb n I3n+1 [A' = 3-(aminomethyl) piperidinium (3AMP), A = methylammonium (MA), n = 1, 2, 4]. Our study demonstrates their irreversible behavior, which suggests pressure/strain engineering could viably improve light-absorber material not only in situ but also ex situ, thus potentially fostering the development of optoelectronic and electroluminescent materials. We discovered that the photoluminescence (PL) intensities are remarkably enhanced by one order of magnitude at mild pressures. Also, higher pressure significantly changes the lattices, boundary conditions of electronic wave functions, and possibly leads to semiconductor-metal transitions. For (3AMP)(MA)3Pb4I13, permanent recrystallization from 2D to three-dimensional (3D) structure occurs upon decompression, with dramatic changes in optical properties.

Thiophene-Based Two-Dimensional Dion-Jacobson Perovskite Solar Cells with over 15% Efficiency.

Two-dimensional (2D) perovskites are emerging photovoltaic materials because of their highly tunable photophysical properties and improved environmental stability in comparison with 3D perovskites. Here, a thiophene-based bulky dication spacer, namely, 2,5-thiophenedimethylammonium (ThDMA), was developed and applicated in 2D Dion-Jacobson (DJ) perovskite. High-quality 2D DJ perovskite, (ThDMA)(MA)n-1PbnI3n+1 (nominal n = 5), with improved crystallinity, preferred vertical orientation, and enlarged spatially resolved carrier lifetime could be achieved by a one-step method using a mixed solvent of DMF/DMSO (v/v, 9:1). The optimized device exhibits a high efficiency of 15.75%, which is a record for aromatic spacer-based 2D DJ perovskite solar cells (PSCs). Moreover, the unencapsulated 2D DJ perovskite devices sustained over 95% of their original efficiency after storage in N2 for 1655 h. Importantly, both the light-soaking stability and thermal stability (T = 80 °C) of the 2D DJ perovksite devices are dramatically improved in comparison with their 3D counterparts. These results indicate that highly efficient and stable 2D DJ PSCs could be achieved by developing thiophene-based aromatic spacers as well as device engineering.

Additive‐Assisted Hot‐Casting Free Fabrication of Dion–Jacobson 2D Perovskite Solar Cell with Efficiency Beyond 16%

2D Dion–Jacobson (DJ) perovskite solar cells (PVSCs) with a high power conversion efficiency (PCE) are currently predominately fabricated via a hot‐casting process. The reason lies in the difficulty in preparing high‐quality perovskite films under mild conditions when the application of divalent ammonium removes the weak interaction from the spacer cation layer. Herein, the morphology of the 2D DJ perovskite film with a rigid piperidinium ring is tuned through a room‐temperature spin‐coating method, with the aid of a methylammonium thiocyanate (MASCN) additive. With the optimized amount of MASCN addition, the perovskite films deposited on the poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA)/poly[(9,9‐bis(30‐(N,N‐dimethylamino)propyl)‐2,7‐uorene)‐alt‐2,7‐(9,9‐dioctylfuorene)] (PFN) substrate exhibit fine crystallinity, preferred orientation, decreased defects, and better energy‐level alignment with the hole transport layer. The device with the inverted planar structure presents a JSC of 17.91 mA cm−2, VOC of 1.19 V, fill factor of 0.76, with a maximum PCE of 16.25%, which is the highest PCE for 2D DJ PVSCs free of hot casting. The unsealed device maintains around 80% of its initial efficiency after 35 days of exposure to air (Hr = 45 ± 5%). A potential route toward high‐performance 2D DJ PVSCs is provided.

Asymmetric alkyl diamine based Dion–Jacobson low-dimensional perovskite solar cells with efficiency exceeding 15%

DMAPA2+ as a diammonium spacer cation to balance high efficiency and high stability for low-dimensional Dion–Jacobson perovskite solar cells.

Nonconfinement Structure Revealed in Dion-Jacobson Type Quasi-2D Perovskite Expedites Interlayer Charge Transport.

Dion-Jacobson (DJ) type 2D perovskites with a single organic cation layer exhibit a narrower distance between two adjacent inorganic layers compared to the corresponding Ruddlesden-Popper perovskites, which facilitates interlayer charge transport. However, the internal crystal structures in 2D DJ perovskites remain elusive. Herein, in a p-xylylenediamine (PDMA)-based DJ perovskite bearing bifunctional NH3 + spacer, the compression from confinement structure (inorganic layer number, n = 1, 2) to nonconfinement structure (n > 3) with the decrease of PDMA molar ratio is unraveled. Remarkably, the nonconfined perovskite displays shorter spacing between 2D quantum wells, which results in a lower exciton binding energy and hence promotes exciton dissociation. The significantly diminishing quantum confinement promotes interlayer charge transport leading to a maximum photovoltaic efficiency of ≈11%. Additionally, the tighter interlayer packing arising from the squeezing of inorganic octahedra gives rise to enhanced ambient stability.