quasi-2D Perovskite Research Articles

Flexible quasi-2D perovskite solar cells with high specific power and improved stability for energy-autonomous drones

Flexible quasi-2D perovskite solar cells with high specific power and improved stability for energy-autonomous drones

High-Quality Solution-Processed Quasi-2D Perovskite for Low-Threshold Lasers.

Spin-coated quasi-two-dimensional halide perovskite films, which exhibit superior optoelectronic properties and environmental stability, have recently been extensively studied for lasers. Crystallinity is of great importance for the laser performance. Although some parameters related to the spin-coating process have been studied, the in-depth understanding and effective control of the acceleration rate on two-dimensional perovskite crystallization during spin-coating are still unknown. Here we investigate the effect of solvent evaporation on the microstructure of the final perovskite films during the spin-coating process. The crystallization quality of the film can be significantly improved by controlling solvent evaporation. As a result, the prepared quasi-2D perovskite film exhibits a stimulated emission threshold (pump: 343 nm, 6 kHz, 290 fs) of 550 nm as low as 16.2 μJ/cm2. Transient absorption characterization shows that the radiative biexciton recombination time is reduced from 738.5 to 438.3 ps, benefiting from the improved crystallinity. The faster biexciton recombination significantly enhanced the photoluminescence efficiency, which is critical for population inversion. This work could contribute to the development of low-threshold lasers.

High-performance quasi-2D perovskite solar cells enabled by using π-conjugated spacer

The excellent photoelectric properties and low fabrication cost of perovskite solar cells have attracted extensive research attention. Despite this, long-term stability issues associated with perovskite solar cells continue to pose a significant barrier to commercialization. A new generation of two-dimensional (2D) and quasi-2D perovskites and newly introduced members of the 2D material family, have attracted growing attention due to their excellent stability and physical properties in contrast to their three-dimensional (3D) counterparts. Herein, we have presented the feasibility of using 4,4[Formula: see text]-dipyridyl as an additive material for quasi-2D perovskite solar cells. As a result of the addition of 4,4[Formula: see text]-dipyridyl, the solar cell device achieves a power conversion efficiency of 17.92% and a fill factor of 76.5%. Additionally, this strategy can be expanded to quasi-2D perovskite solar cells with an open-circuit voltage of 1.05[Formula: see text]V.

Highly stable and sensitive broadband photodetector based on BA2MAPb2I7/Si heterojunction

Quasi-2D perovskites have gained significant attention as promising two-dimensional materials for optoelectronic applications. They offer unique optical and electrical properties as well as enhanced stability compared to their 3D counterparts. In this study, we present the successful fabrication of a novel photodetector based on a BA2MAPb2I7/Si heterojunction. The optoelectronic properties of the BA2MAPb2I7/Si-based photodetector demonstrate its high sensitivity across a broad range of incident wavelengths spanning from 365 nm to 850 nm. Notably, the fabricated device exhibits an exceptional responsivity of 3.53 A/W for 850 nm radiation, surpassing the typical few mA/W responsivities achieved by a majority of previously reported perovskite-based vertical photodetectors. Furthermore, the device shows a rapid response of approximately 25.9 μs. These results highlight the potential of our fabrication approach to realize highly sensitive broadband photodetectors using a simple and cost-effective process, making them suitable for integration with Si-based electronics.

Phosphonic acid based bifunctional additive for high-performance blue perovskite light-emitting diodes

Quasi-two-dimensional (quasi-2D) Ruddlesden-Popper (RP) phase perovskite materials exhibiting quantum confinement effect are promising candidates for realizing high-performance blue perovskite light-emitting diodes (PeLEDs). However, the performance of blue PeLEDs based on quasi-2D perovskites remains unsatisfactory, as it is limited by non-ideal charge transport, energy transfer, and defect. Here, a series of bifunctional phosphonic acid additives with synergistic effects are reported. These additives passivate defects and reduce non-radiative recombination losses by coordinating PO functional group with unsaturated Pb2+, and they promote energy transfer and radiative recombination by optimizing the proportion of small n phases and large n phases. Owing to the synergistic effects of passivation and energy transfer, optimized blue PeLEDs (∼486 nm) with 3-phosphonopropionic acid (3-PA) additive exhibits a champion EQE of 13.11%, which is exceptionally high for blue PeLEDs.

High–Quality and Stable Quasi‐2D Perovskite Film Prepared by Introducing Alkali Metal Ion Additive

AbstractDue to the excellent stability, researchers have shown great interest in quasi two–dimensional (2D) perovskite in recent years. However, the poor film quality and low photoelectric conversion efficiency (PCE) of 2D perovskite solar cells are still a major issue that restricts them from catching up with three–dimensional (3D) perovskite. Herein, we introduce sodium iodide as an additive to improve the surface coverage of 2D perovskite ((BA)2(MA)3Pb4I13) films and reduce the number of grain boundaries. Steady–state photoluminescence (PL) and ultraviolet photoelectron spectroscopy (UPS) indicate that non–radiative defects are suppressed and the band alignment is regulated. After modified by NaI, the film surface coverage enhances and the number of holes decreases. As a result, the PCE of device with NaI increases from 13.63 % to 16.40 % at optimal concentration, and the hysteresis effect is also suppressed. Besides, the humidity and thermal stability of perovskite are enhanced. The device with NaI modification can keep 80 % of initial efficiency, compared to 30 % for reference device after stored 30 days under ambient air condition. This work provides a simple method to improve the quality of quasi 2D perovskite films.

Multi-functional ion-pairing additive for efficient quasi-2D perovskite light-emitting diodes and solar cells

Due to their unique quantum confinement, dielectric coupling, and tunable high-efficiency electroluminescence, quasi-two-dimensional (quasi-2D) perovskite light-emitting diodes (PeLEDs) have attracted considerable attention. However, imperfections in perovskite thin films introduced during the solution-based fabrication process lead to significant non-radiative recombination, hindering device performance. Addressing this challenge is crucial for realizing high-performance quasi-2D PeLEDs. In this study, we introduce an ion-pairing-type additive, 6-maleimidohexanehydrazide trifluoroacetate (EMCH-TFA), designed to cooperatively passivate defects in quasi-2D perovskites. The diverse functional groups (–COOH, –NH2, -CF3) on EMCH-TFA could provide disparate modification to perovskite, among which the CO group tends to coordinate with the uncoordinated Pb2+ ions, thereby passivating the defects in the perovskite crystal. Additionally, the –NH2 and -CF3 groups establish hydrogen bonds with Br- ions and BA+ spacer cations, respectively. This multifaceted approach suppresses the formation of the small n phase and induces alterations in the crystalline state by interacting with numerous sites in perovskites, including A’, B, and X sites. Consequently, the quasi-2D PeLED based on BA2Csn-1PbnBr3n+1 exhibits enhanced brightness, achieving a current efficiency of 66.7 cd/A and an impressive external quantum efficiency of 19.77 %.

Enhanced performance and stability of quasi two-dimensional perovskite solar cells by conductive phosphine oxide

Recently, quasi two-dimensional (quasi-2D) perovskite solar cells (PSCs) have been paid more attentions due to their good stability. While the efficiency of 2D PSCs is lower than that of 3D ones due to their poor charge transport property. Here we introduced a conductive material of 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene (SPPO13) into the precursor solution of quasi-2D perovskite GAMA5Pb5I16 (GA = guanidinium, MA = methylammonium) to improve the charge transfer property. The efficiency of the PSCs with SPPO13 is increased to 18.58 % from 16.97 % for the control, which is resulting from the enlarged grain size, increased electrical conductivity, and reduced trap state density induced by the addition of SPPO13. Moreover, the additon of SPPO13 improves the stability of the devices. The normalized PCE of the devices with SPPO13 keeps 90 % of the original value after aging for 30 days in atmosphere. This study provides a novel way to enhance the charge transfer property of 2D perovskite by conductive material for enhanced efficiency and stability of quasi-2D PSCs.

Ground state structure and optoelectronic properties of novel quasi-2D layered halide perovskites CsPb2X5 (X= Cl, Br, I) via first principle calculations

The ground state structure and optoelectronic properties of novel quasi-2D layered halide perovskites CsPb2X5 (X= Cl, Br, I) are investigated for the possible optoelectronic applications in light emitting, photodetectors, photoemission, and photovoltaic (PV) devices using first principle-based calculations of the density functional theory (DFT). In the structure composition of CsPb2X5, 2Pb2+ atoms coordinated with eight X- anions build [Pb2X5]- polyhedral layers, where two layers of [Pb2X5]- polyhedron are separated by Cs+ (spacer cation) layers. The band gap nature of the studied semiconductors is indirect and spin orbit coupling (SOC) effect reduces the band gaps and splits the Pb-p and X-p orbitals at the edges of conduction and valence bands respectively. The wide and suitable band gaps of CsPb2X5 enable them for advanced technological applications in photodetectors, transistors, and optoelectronic devices. The dielectric functions, exciton binding energies, and carrier's effective masses show that CsPb2X5 are suitable materials for optoelectronic, photodetectors, and light emitting devices.

Enhancing Energy Transfer through Structure Reconstruction of Quasi-2D Perovskites for Highly Efficient Light-Emitting Diodes

Enhancing Energy Transfer through Structure Reconstruction of Quasi-2D Perovskites for Highly Efficient Light-Emitting Diodes

Thermally Evaporated Blue Quasi-Two-Dimensional Perovskite Light-Emitting Diodes via Low-Dimensional Phase Distribution Arrangement.

Perovskite light-emitting diodes (PeLEDs) have shown great potential in the display domain due to their wide color gamut, narrow emission, and low cost. In current PeLEDs manufacturing methods, thermal evaporation shows great competitiveness with its advantages of easy patterning, production line compatibility, and solvent-free processability. However, the development of thermally evaporated blue PeLEDs is limited by their low radiative recombination rate and high defect density. Herein, we report high-performance thermally evaporated blue PeLEDs by in situ introduction of ammonium cations. We confirm that phenethylammonium (PEA+) has lower adsorption energy, which significantly reduces the low-n phases in a quasi-2D perovskite film. The energy transfer rate is also promoted by the PEA+ addition. As a result, we fabricate blue PeLEDs with an external quantum efficiency of 1.56% by thermal evaporation. The strategy of arranging phase distribution could benefit the industrialization of full-color PeLEDs.

Charge Injection and Auger Recombination Modulation for Efficient and Stable Quasi-2D Perovskite Light-Emitting Diodes.

The inefficient charge transport and large exciton binding energy of quasi-2D perovskites pose challenges to the emission efficiency and roll-off issues for perovskite light-emitting diodes (PeLEDs) despite excellent stability compared to 3D counterparts. Herein, alkyldiammonium cations with different molecular sizes, namely 1,4-butanediamine (BDA), 1,6-hexanediamine (HDA) and 1,8-octanediamine (ODA), are employed into quasi-2D perovskites, to simultaneously modulate the injection efficiency and recombination dynamics. The size increase of the bulky cation leads to increased excitonic recombination and also larger Auger recombination rate. Besides, the larger size assists the formation of randomly distributed 2D perovskite nanoplates, which results in less efficient injection and deteriorates the electroluminescent performance. Moderate exciton binding energy, suppressed 2D phases and balanced carrier injection of HDA-based PeLEDs contribute to a peak external quantum efficiency of 21.9%, among the highest in quasi-2D perovskite based near-infrared devices. Besides, the HDA-PeLED shows an ultralong operational half-lifetime T50 up to 479h at 20mA cm‒2, and sustains the initial performance after a record-level 30000 cycles of ON-OFF switching, attributed to the suppressed migration of iodide anions into adjacent layers and the electrochemical reaction in HDA-PeLEDs. This work provides a potential direction of cation design for efficient and stable quasi-2D-PeLEDs.

Suppressing interfacial nonradiative recombination by alkali hydroxides for efficient blue perovskite light-emitting diodes

Blue perovskite light-emitting diodes (PeLEDs) provide unlimited possibility in the field of optoelectronic devices due to their excellent characteristics. However, the widely used hole-transport material, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), has strong acidity and poor conductivity which deteriorate the efficiency and stability of perovskite devices. In this work, we modified PEDOT:PSS layer using alkalis, LiOH, NaOH, and KOH, to address these issues. Our findings indicated that the indium defect from indium tin oxide substrate was passivated after the introduction of LiOH, which resulted in the suppression of nonradiative recombination. In addition, the conductivity was improved owing to the increased phase separation of PEDOT:PSS. Taking advantage of optimized interface, the small-n phases of quasi-two-dimensional (quasi-2D) perovskite films were redistributed in quantities and dimensions. As results of these improvements, blue PeLEDs possessed the external quantum efficiencies of 5.95 % and an extended half-lifetime with emission-light wavelength of 473 nm. These findings offer an effective strategy to achieve highly efficient blue light-emitting diode.

Manipulation of Crystal Orientation and Phase Distribution of Quasi-2D Perovskite through Synergistic Effect of Additive Doping and Spacer Engineering.

The diammonium precursor 1,4-phenylenedimethanammonium (PDMA) was used as a large organic spacer for the preparation of Dion-Jacobson-type quasi-2D perovskites (PDMA)(MA)n-1PbnI3n+1 (MA = methylammonium). Films with composition ⟨n⟩ = 5 comprised randomly orientated grains and multiple microstructural domains with locally differing n values. However, by mixing the Dion-Jacobson-type spacer PDMA and the Ruddlesden-Popper-type spacer propylammonium (PA), the crystal orientation in both the vertical and the horizonal directions became regulated. High crystallinity owing to well-matched interlayer distances was observed. Combining this spacer-engineering approach with the addition of methylammonium chloride (MACl) led to full vertical alignment of the crystal orientation. Moreover, the microstructural domains at the substrate interface changed from low-n (n = 1, 2, 3) to high-n (n = 4, 5), which may be beneficial for hole extraction at the interface between perovskite and hole transport layer due to a more finely tuned band alignment. Our work sheds light on manipulating the crystallization behavior of quasi-2D perovskite and further paves the way for highly stable and efficient perovskite devices.

Improved Performance and Stability of Quasi-Two-Dimensional Perovskite Solar Cells by Post-treatment with Acetaminophen.

Recently, perovskite solar cells (PSCs) based on quasi-two-dimensional (quasi-2D) perovskites have drawn more attention due to their excellent stability, although their efficiencies are still lower than those of 3D ones. Here we applied post-treatment of 2D perovskite GAMA5Pb5I16 (GA = guanidinium, MA = methylammonium) films with acetaminophen (AMP) to improve their performance. The efficiency of the solar cells with 2 mg/mL AMP post-treatment increased to 18.01% from 16.72% for those without post-treatment. The efficiency improvement results from the enlarged grain size, reduced trap state density, and better energy level matching after AMP post-treatment. In addition, the stability of the solar cells is improved. The solar cells with AMP post-treatment maintain 91% of the original power conversion efficiency value after aging for 30 days in the atmosphere. This work opens a new approach for the efficiency and stability enhancement of quasi-2D PSCs.

Element Regulation and Dimensional Engineering Co-Optimization of Perovskite Memristors for Synaptic Plasticity Applications.

Capitalizing on rapid carrier migration characteristics and outstanding photoelectric conversion performance, halide perovskite memristors demonstrate an exceptional resistive switching performance. However, they have consistently faced constraints due to material stability issues. This study systematically employs elemental modulation and dimension engineering to effectively control perovskite memristors with different dimensions and A-site elements. Compared to pure 3D and 2D perovskites, the quasi-2D perovskite memristor, specifically BA0.15MA0.85PbI3, is identified as the optimal choice through observations of resistive switching (HRS current < 10-5 A, ON/OFF ratio > 103, endurance cycles > 1000, and retention time > 104 s) and synaptic plasticity characteristics. Subsequently, a comprehensive investigation into various synaptic plasticity aspects, including paired-pulse facilitation (PPF), spike-variability-dependent plasticity (SVDP), spike-rate-dependent plasticity (SRDP), and spike-timing-dependent plasticity (STDP), is conducted. Practical applications, such as memory-forgetting-memory and recognition of the Modified National Institute of Standards and Technology (MNIST) database handwritten data set (accuracy rate reaching 94.8%), are explored and successfully realized. This article provides good theoretical guidance for synaptic-like simulation in perovskite memristors.

Unveiling the Intrinsic Photophysics in Quasi-Two-Dimensional Perovskites.

The two-dimensional (2D) perovskites have drawn intensive attention due to their unique stability and outstanding optoelectronic properties. However, the debate surrounding the spatial phase distribution and band alignment among different 2D phases in the quasi-2D perovskite has created complexities in understanding the carrier dynamics, hindering material and device development. In this study, we employed highly sensitive transient absorption spectroscopy to investigate the carrier dynamics of (BA)2(MA)n-1PbnI3n+1 quasi-2D Ruddlesden-Popper perovskite thin films, nominally prepared as n = 4. We observed the carrier-density-dependent electron and hole transfer dynamics between the 2D and three-dimensional (3D) phases. Under a low carrier density within the linear response range, we successfully resolved three ultrafast processes of both electron and hole transfers, spanning from hundreds of femtoseconds to several picoseconds, tens to hundreds of picoseconds, and hundreds of picoseconds to several nanoseconds, which can be attributed to lateral-epitaxial, partial-epitaxial, and disordered-interface heterostructures between 2D and 3D phases. By considering the interplay among the phase structure, band alignment, and carrier dynamics, we have proposed material synthesis strategies aimed at enhancing the carrier transport. Our results not only provide deep insights into an accurate intrinsic photophysics of quasi-2D perovskites but also inspire advancements in the practical application of these materials.

Enhancing energy transfer via inhibition defect density of coupled quasi-2D perovskite layers for efficient sky-blue light-emitting diodes

Metal halide perovskite materials have emerged as unique and promising candidates for full-color display and solid-state lighting applications. While substantial progress has been made in developing green, red and near-infrared perovskite light-emitting diodes (PeLEDs) with external quantum efficiency (EQE) approaching their theoretical upper limit, the performance of blue PeLEDs is still lagging far behind. Here, synergistic long and short hydrobromide chains are strategically introduced into the perovskite to regulate composition and dimensional engineering for promoting coupled quasi-two-dimensional perovskite thin films with enhanced photoluminescence quantum yield (PLQY) and reduced trap state density. The inclusion of the hydrobromide can also simultaneously passivate the perovskite defects by reducing nonradiative recombination loss and increasing the formation of n >1 phases for efficient exciton energy transfer. Encouraged by these findings, we finally demonstrate the most stable sky-blue PeLEDs to date with a half-lifetime of 515 min at high external quantum efficiency (EQE＞10 %), emitting at 486 nm with a peak EQE of up to 15.6 %.

Effect of phase distribution and defect passivation on amplified spontaneous emission of quasi-2D Dion–Jacobson perovskite

Quasi-2D Dion–Jacobson (DJ) halide perovskites with large exciton binding energy, self-assembled quantum wells, and high quantum yield attract growing attention in light-emitting diodes and solar devices. DJ-layered perovskites have the eliminated van der Waals gap and show improved photophysical features. However, there are a variety of defects and complex phase distributions produced during the solution procedure and the fast crystal development. In this paper, we reveal the effect of phase distribution and defect passivation on amplified spontaneous emission of quasi-2D perovskite (PDMA)(MA)2Pb3Br10 thin films through solvent engineering and additive methods, by establishing the correlation between the precursor compositions and the photophysical performance of the layered DJ perovskites. The energy transfer rate and the photoluminescence quantum yield increase due to the spatially homogeneous domain distribution and the reduced defect density after the addition of KBr in the DMSO:DMF. More importantly, we realize green amplified spontaneous emission and single-mode vertical-cavity surface-emitting lasing with low thresholds of 8.8 and 10.5 μJ cm−2, respectively. This work provides a guideline to achieve low-threshold multicolor lasers based on DJ perovskites.

Phase distribution management in quasi-2D perovskite films toward highly efficient amplified spontaneous emission pumped by nanosecond pulsed laser

Phase distribution management in quasi-2D perovskite films toward highly efficient amplified spontaneous emission pumped by nanosecond pulsed laser