Chen Weijie

Nature Communications, Published online: 06 October 2021; doi:10.1038/s41467-021-26121-1

A visibly clear and flexible radiative cooling metamaterial is demonstrated using optical modulator-infiltrated silica aerogel microparticles in a silicone elastomer. The metamaterials deployed in solar cells and windows can effectively suppress the rise in temperature under solar irradiation, thereby mitigating the performance degradation of solar cells by heating issues and suppressing the rise in temperature of indoor air.

Abstract

The study of transparent daytime radiative cooling with no additional energy consumption is a promising area of research. Its applications include solar cells and building and automobile windows that are prone to heating issues. Ubiquitous applications necessitate the development of metamaterials with high mechanical flexibility in a scalable manner while overcoming translucence. In this study, visibly clear and flexible radiative cooling metamaterials have been developed using a newly designed optical modulator filled into randomly distributed silica aerogel microparticles in a silicone elastomer. The optical modulator effectively suppresses visible light scattering, thus enabling higher loading of silica aerogel microparticles while securing visible clarity. The significant suppression of the rise in temperature by the metamaterial is verified using both indoor and outdoor experiments. The visibly clear metamaterials deployed in solar cells and windows can effectively suppress the rise in temperature under solar irradiation, thereby mitigating the performance degradation of solar cells by heating issues and suppressing the rise in temperature of indoor air.

This study introduces an octyl-diammonium lead iodide (ODAPbI₄) interlayer onto the hole-transporting layer, which significantly reduces nonradiative recombination of wide-bandgap perovskite devices, enhancing the efficiency of wide-bandgap devices beyond 21%. By coupling a semitransparent device with a Cu₂ZnSn(S,Se)₄ (CZTSSe) cell, a four terminal perovskite/CZTSSe tandem cell with a power conversion efficiency of 22.27% is achieved.

Abstract

Wide-bandgap perovskites have attracted substantial attention due to their important role in serving as a top absorber in tandem solar cells (TSCs). However, wide-bandgap perovskite solar cells (PVSCs) typically suffer from severe non-radiative recombination loss and therefore exhibit high open-circuit voltage (V _OC) deficits. To address these issues, a 2D octyl-diammonium lead iodide interlayer is adopted onto the hole-transporting layer to induce the formation of an ultrathin quasi-2D perovskite that is close to the hole-selective interface. This approach not only accelerates hole transfer and retards hole accumulation but also reduces the trap density in the perovskite layer on top, thereby efficiently suppresses non-radiative recombination pathways. Consequently, the champion wide-bandgap device (≈1.66 eV) exhibits a power conversion efficiency (PCE) of 21.05% with a V _OC of 1.23 V, where the V _OC deficit of 0.43 V is among the lowest values for inverted wide-bandgap PVSCs. Moreover, by stacking a semi-transparent perovskite top cell on a 1.1 eV Cu₂ZnSn(S,Se)₄ (CZTSSe) bottom cell, a 22.27% PCE was achieved on a perovskite/CZTSSe four-terminal tandem solar cell, paving the way for all-solution-processed, low-cost, and efficient TSCs with mitigated energy loss in the wide-bandgap top cells.

A facile strategy to achieve both proper solubility and pre-aggregation in non-halogenated solvents by selecting suitable donor/acceptor materials and subtle tuning of solvent compositions was developed. The derived solar cells achieve a high efficiency up to 18%, representing the highest value reported for non-halogenated solvent processed devices.

Abstract

Using non-halogenated solvents to process organic solar cells is preferable because they are less harmful to human health. However, it is challenging to mitigate the delicate trade-offs between solubility and pre-aggregation of organic semiconductors to maintain similar high device efficiencies as those processed by chlorinated solvents. The need for rigorous control of the kinetics between processing temperature and delay time inevitably complicates device processing for achieving reproducible performance. Herein, the authors develop a facile method to achieve proper solubility and pre-aggregation in non-halogenated solvents by selecting suitable donor/acceptor materials and subtle tuning of solvent compositions. This results in films with a high degree of ordering and suitably sized phase separation. Solar cells derived from this process can achieve a high power conversion efficiency up to 18%, which is the highest value reported for non-halogenated solvent processed devices. This impressive result is achieved through synergistically reduced non-radiative loss and enhanced charge generation.

A library of 2D and quasi-2D halide perovskite lateral heterostructures is synthesized, and the platform is utilized to analyze the impact of organic cation and inorganic layer thickness on bromide–iodide interdiffusion kinetics. This quantitative halide diffusion study on perovskites will aid in driving future innovations toward novel material design and optoelectronic device applications.

Abstract

Anionic diffusion strongly impacts the stability of halide perovskite materials, but it is still not well understood. Here, a quantitative investigation of in-plane thermally driven anionic inter-diffusion in a series of novel 2D and quasi-2D halide perovskites lateral heterostructures is reported. The calculated diffusion coefficients (D) reveal the inhibition of Br–I inter-diffusion with bulky π-conjugated organic cations compared with short-chain aliphatic organic cations. Furthermore, halide diffusion is found to be faster in quasi-2D (n > 1) than 2D perovskites (n = 1). The increment becomes less apparent as the “n” number increases, akin to the quantum confinement effect observed for band gaps. These trends are rationalized by molecular dynamics simulations of free energy barriers for halide diffusion that reveal mechanisms for suppressing diffusion. This work provides important fundamental insights on the anionic migration and diffusion process in halide perovskite materials.

How to obtain and understand in situ GIWAXS data is highlighted, and recent results of in situ GIWAXS studies on versatile perovskite photovoltaic systems that elucidate crystallization and film formation mechanisms in terms of material compositions, film deposition methods, and film treatment procedures are summarized and assessed.

Abstract

Metal halide perovskites are of fundamental interest in the research of modern thin-film optoelectronic devices, owing to their widely tunable optoelectronic properties and solution processability. To obtain high-quality perovskite films and ultimately high-performance perovskite devices, it is crucial to understand the film formation mechanisms, which, however, remains a great challenge, due to the complexity of perovskite composition, dimensionality, and processing conditions. Nevertheless, the state-of-the-art in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) technique enables one to bridge the complex information with device performance by revealing the crystallization pathways during the perovskite film formation process. In this review, the authors illustrate how to obtain and understand in situ GIWAXS data, summarize and assess recent results of in situ GIWAXS studies on versatile perovskite photovoltaic systems, aiming at elucidating the distinct features and common ground of film formation mechanisms, and shedding light on future opportunities of employing in situ GIWAXS to study the fundamental working mechanisms of highly efficient and stable perovskite solar cells toward mass production.

Building up on the excellent optical properties of perovskite materials, the electron and hole spin dynamics provide fundamental insights into the carrier–nuclear spin system. In the model perovskite, bulk FA_0.9Cs_0.1PbI_2.8Br_0.2, Landé factors, key spin relaxation times, and mechanisms are determined. Optically detected NMR reveals the dominance of the lead spin hyperfine interaction at the top of the valence band.

Abstract

The outstanding optical quality of lead halide perovskites inspires studies of their potential for the optical control of carrier spins as pursued in other materials. Entering largely uncharted territory, time-resolved pump–probe Kerr rotation is used to explore the coherent spin dynamics of electrons and holes in bulk formamidinium caesium lead iodine bromide (FA_0.9Cs_0.1PbI_2.8Br_0.2) and to determine key parameters characterizing interactions of their spins, such as the g-factors and relaxation times. The demonstrated long spin dynamics and narrow g-factor distribution prove the perovskites as promising competitors for conventional semiconductors in spintronics. The dynamic nuclear polarization via spin-oriented holes is realized and the identification of the lead (²⁰⁷Pb) isotope in optically detected nuclear magnetic resonance proves that the hole–nuclei interaction is dominated by the lead ions. A detailed theoretical analysis accounting for the specifics of the lead halide perovskite materials allows the evaluation of the underlying hyperfine interaction constants, both for electrons and holes. Recombination and spin dynamics evidence that at low temperatures, photogenerated electrons and holes are localized at different regions of the perovskite crystal, resulting in their long lifetimes up to 44 μs. The findings form the base for the tailored development of spin-optoelectronic applications for the large family of lead halide perovskites and their nanostructures.

Publication date: 1 December 2021

Source: Electrochimica Acta, Volume 398

Author(s): Ramesh Kumar, Prem Sagar Shukla, G.D. Varma, Monojit Bag

Power conversion efficiency of the Cs _x FA_1−x Pb(I_0.94Br_0.06)₃-based perovskite solar cells (PSCs) as a function of time and a cross-sectional transmission electron microscopy (TEM) image to demonstrate stable interface of K5B active layer-based PSC after 1128 h.

Formamidinium lead iodide (FAPbI₃) is ideal for highly efficient and operationally stable perovskite solar cells (PSC). However, a primary challenge for FAPbI₃ PSC is to suppress the phase transition from the photoactive black phase into the yellow nonperovskite δ-phase. The preparation of Cs-containing mixed FAPbI₃ perovskite by cation stoichiometric engineering is demonstrated and the influence of the Cs/FA ratio on its phase stability and device performance is discussed. By exploring the optimal ratio of Cs and FA cations in Cs _x FA_1−x Pb(I_0.94Br_0.06)₃ perovskite, an inverted planar device with Cs_0.17FA_0.83Pb(I_0.94Br_0.06)₃ composition shows the best power conversion efficiency (PCE) of 16.5% in an active area of 1.08 cm². More importantly, the Cs_0.17FA_0.83Pb(I_0.94Br_0.06)₃ perovskite photoactive layer showed remarkable long-term stability, maintaining 88.1% of its initial efficiency for 1128 h in the presence of moisture and oxygen and without any encapsulation. The excellent long-term stability is found to originate from the appropriate tolerance factor and low thermodynamic decomposition energy, which underpins the strong potential for the commercialization of Cs-containing mixed FAPbI₃ PSCs.

The low-cost, scalable, and high-performing ZnOSnO₂ cascaded electron transport layer based on spray coating and blade coating is developed and demonstrates the superior advantages in electrons’ extraction, energy band matching, interface stability, and crystallization tailoring for perovskite films. Further combined with the same scalable blade-coated perovskite film and hole transport layer, efficient planar modules with high reproducibility are facilely realized.

Perovskite solar cells are the fastest-growing photovoltaic technology in recent years. However, together with the stability, the low-cost and high-quality preparation of large-area modules still limits their commercialization process. Herein, a scalable and high-performance ZnOSnO₂ cascade double-layer electron transport layer (ETL) for efficient and stable perovskite modules is reported. The cascaded ETL is fabricated using a simple spray pyrolysis coating combined with the blade coating process, which not only effectively improves the interface stability by avoiding the protonation of ZnO to maintain its high electron mobility, but also provides a much smoother surface for the crystallization of perovskites. In addition, the well-matched conduction band level between SnO₂ and perovskites ensures the improvement of open-circuit voltage. Subsequently, combined with the blade-coated perovskite layer and hole transport layer film, large-area planar perovskite modules are successfully prepared. These high-quality films enable the perovskite solar modules to achieve impressive efficiencies of 17.8% in the module size 6 × 6 cm² and 16.6% in a size of 10 × 10 cm². The obtained module also shows excellent reproducibility and stability. The high-performance ETL and the related deposition method developed in this work are promising for applications in the industrial scalable perovskite modules’ fabrication.

Herein, a systematic overview of commercialization of perovskite PV technology is provided, including module architecture, laser scribing, cost, and life cycle. The key strategies for fabrication, stability, and performance are also discussed. In addition, the current issues and future perspective are provided toward commercialization of perovskite solar modules in the near future.

The commercialization of perovskite photovoltaic technology is dependent on the development of high-efficiency, stable, and large-area solar modules. Despite the rapid rise in efficiencies of laboratory-scale perovskite solar cells (PSCs), there is still a big gap in the transition from small-area devices to large-area perovskite solar modules (PSMs). Herein, recent progresses on scaling-up PSMs are reviewed: first, multifarious scalable preparation methods, solvent engineering, and corresponding morphology control strategies for large-area homogeneous perovskite films are summarized. Various charge carrier transport materials, electrode materials, and their scaling methods for high-efficiency and stable PSMs are then outlined and the device structure design of PSMs is discussed. Finally, the current strategies for optimizing the environmental stability of devices are highlighted, and packaging for reducing lead leakage during operation is discussed.

High-quality (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I₀.₈₃Br_0.17)₃ perovskite films are fabricated by solvent volatilization. This method does not need an antisolvent technique and presents significant potential for large-scale and large-area device fabrication. A high power conversion efficiency of 20.6% is obtained by the films. A large area perovskite film of 10 × 10 cm² can be fabricated by the method.

Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA_0.83MA_0.17)_0.95Cs_0.05Pb(I_0.83Br_0.17)₃ (CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI _x Cl _y Br _z during annealing, leading to high-quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing-incidence wide-angle X-ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large-scale production.

A sputtered NiO _x seed layer is employed to promote the adsorption of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayers. The resulting high-density MeO-2PACz provides an increased passivation, an enhanced hole-selectivity, a favorable energy-level alignment, and a robust physical contact between perovskite and indium tin oxide. The corresponding inverted perovskite solar cell exhibits an impressive efficiency of 19.9%.

Self-assembled monolayers (SAMs) have emerged as effective carrier transport layers in perovskite (PVK) solar cells because of their unique ability to manipulate interfacial property, as well as simple processing and scalable fabrication. However, the defects and pinholes derived from their sensitive adsorption process inevitably deteriorate the final device performance. Herein, a sputtered nickel oxide (NiO _x ) interlayer is used as a seed layer to promote the adsorption of the [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) SAM on the indium tin oxide (ITO) substrate. The promoted adsorption is attributed to the enhanced tridentate binding between MeO-2PACz and NiO _x relative to the conventional bidentate binding between MeO-2PACz and ITO. In addition, the NiO _x modification can simultaneously improve the passivation ability and hole-selectivity of the MeO-2PACz, provide a favorable energy-level alignment at the ITO/PVK interface, and prevent a direct contact between PVK and ITO. As a consequence, this NiO _x -seeded MeO-2PACz hole transport layer enables a significantly enhanced power conversion efficiency of 19.9% in comparison with 18.4% of the control device. This work provides an effective strategy to improve the performance of the SAM-based photoelectric device.

This review presents state-of-the-art developments on 2D metal-halide perovskite solar cells. The basic crystal structure, properties, and device photovoltaic performance on 2D perovskites are discussed in detail. Besides, the confronting challenges and corresponding strategies are proposed to offer insight into the underlying properties of this family of materials.

Abstract

2D metal-halide perovskites have attracted intense research interest due to superior long-term stability under ambient environments. Compared to their 3D analog, the alternate arrangement of organic and inorganic layers leads to forming a multilayer quantum well (MQW), which endows 2D perovskites with anisotropic optoelectronic properties. In addition, the spacer layer functions as a hydrophobic barrier to effectively prevent 2D perovskite films from ion migration and moisture penetrating, thus realizing outstanding stability. Recently, 2D perovskites have been widely developed with abundant species. The stunning photovoltaic performance with the coexistence of long-term stability and high-power conversion efficiency (PCE) has been realized in 2D perovskite solar cells (PSCs), which paves an avenue for commercialization of PSCs. This review begins with an introduction of crystal structure and crystallization kinetics to illustrate the unique layer characters in 2D perovskites. Then, electron structure, excitons, dielectric confinement, and intrinsic stability properties are discussed in detail. Next, the photovoltaic performance based on recent Ruddlesden–Popper (RP), Dion–Jacobson (DJ), and alternating cations in the interlayer (ACI) phase 2D-PSCs is comprehensively summarized. Finally, the confronting challenges and strategies toward structural design and optoelectronic studies of 2D perovskites are proposed to offer insight into the advanced underlying properties of this family of materials.

Self-polymerized monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) is incorporated into perovskite films by the antisolvent additive engineering, attributing to uniform composition distribution, improved crystallinity, and phase stability. Meanwhile, the defects density and recombination is reduced due to the strong interactions with DMAEMA. Finally, the high performance and stability perovskite solar cells are achieved.

Abstract

While there is promising achievement in terms of the power conversion efficiency (PCE) of perovskite solar cells (PSCs), long-term stability has been considered the main obstacle for their practical application. In this work, the authors demonstrate the small monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) with unsaturated carboxylic acid ester bond in the antisolvent for perovskite formation to improve the PCE and stability. The results show that DMAEMA is self-polymerized and uniformly distributed in the film, contributing to the improved crystallinity of the perovskites. Equally important, it is found that there are newly established interactions of Pb²⁺ and DMAEMA, and iodine and ternary amine between DMAEMA and perovskites, which improves the uniformity of the lead (II) iodide vertical distribution along with the films and thus phase stability, as well as largely decreases defects density in the film. Overall, the inverted PSCs with DMAEMA exhibit a open-circuit voltage of 1.10 V, short-circuit current of 23.86 mA cm⁻², fill factor of 0.82, and finally PCE reaches 21.52%. Meanwhile, the PSC stability is significantly improved due to the inhibition of the formation of iodine, reduction of the uncoordinated Pb²⁺, and suppression of phase segregation.

In addition to P-Pb coordination, there is a hydrogen bond between F⁻ and MA⁺/FA⁺ as well as an ionic bond between F⁻ and Pb²⁺ for perovskite/fluorinated black phosphorene (F-BP), thereby achieving high PCE (22.06%). Significantly, F-BP devices exhibit improved humidity and shelf-life stabilities due to the excellent ambient stability of F-BP nanosheets, resulting from antioxidation and antihydration behavior of fluorine adatoms.

Abstract

Extraordinary electronic and photonic features (e.g., tunable direct bandgap, high ambipolar carrier mobility) render few-layer black phosphorus (BP) nanosheets/quantum dots an important optoelectronic material. However, most of the BP applied in metal halide perovskite solar cells (PSCs) are produced by sonication-assisted liquid exfoliation, which inevitably brings inferior electronic properties, thus leading to limited beneficial effects. Furthermore, this study uncovers that the intrinsic instability of BP nanosheets sandwiched between (CsFAMA)Pb(BrI)₃ perovskite and spiro-OMeTAD has a deleterious effect on the performance stabilization of PSCs. To address the above constraints, a feasible strategy herein is developed by introducing high-quality fluorinated BP (F-BP) nanosheets synthesized by one-step electrochemical delamination. In addition to P-Pb coordination, there is a strong hydrogen bond between F⁻ and MA⁺/FA⁺ as well as an ionic bond between F⁻ and Pb²⁺ for the perovskite/F-BP interface, thus leading to fewer interfacial traps than perovskite/BP, which is responsible for the highest power conversion efficiency (22.06%) of F-BP devices. More importantly, F-BP devices exhibit significantly improved humidity and shelf-life stabilities due to the excellent ambient stability of F-BP, resulting from the antioxidation and antihydration behavior of fluorine adatoms. Overall, the findings provide a promising strategy to simultaneously enhance the photovoltaic performance and long-term stability of BP-based PSCs.

To understand the nature of hysteresis, theoretical mechanisms and experimental measurements are provided based on a combination of first-principles simulations, cross-section scanning electron microscopy images, and time-dependent photocurrent measurements. The defect assistance ion-migration process could be the primary contribution to hysteresis. The defect density is reduced via the in situ passivation of PbI₂ crystals, which prevents the migration of ions effectively, and the hysteresis index is decreased from 22.43% to 1.04%.

Abstract

As one of the most promising photovoltaic materials, the efficiency of inorganic–organic hybrid halide perovskite solar cells (PSCs) has reached 25.5% in 2020. However, the stability and hysteresis remain primary challenges before it can become a commercial photovoltaic technology. Therefore, those issues have drawn significant attention for photovoltaic applications. In this work, a study of the PSCs hysteresis improvement is presented based on a combination of first-principles simulations, scanning electron microscopy images, and time-dependent photocurrent measurements. It indicates the hysteresis led by the ion migration and accumulation is mainly localized at the two interfaces: one is between electron transport layer and active layer, and the other is between active layer and hole transport layer. Considering the massive defects at the grain boundaries (GBs), they lower the potential barriers significantly. The defect density at GBs is therefore reduced via the in situ passivation of PbI₂ crystals. The hysteresis index is decreased from 22.43% down to 1.04%, and results in an improvement in efficiency from 17.12% up to 20.10%. Following the understanding of defect-induced hysteresis, an approach to improve the hysteresis is provided, which can be integrated into the fabrication process and widely applied to enhance the performance of PSCs.

The electron transport layer (ETL) plays a crucial part in extracting electrons and optimizing interfacial contact for perovskite solar cells (PVSCs). Herein, the EVA is introduced into PC₆₁BM to promote the orderly molecular stacking of ETLs. The PC₆₁BM:EVA-based MAPbI₃ PVSCs deliver a champion efficiency of 19.32% and regain 80% of initial efficiency after storage under 52% humidity for 1500 h.

Abstract

The electron transport layer (ETL) plays a crucial part in extracting electron carriers while optimizing the interfacial contact of perovskite/electrode in planar heterojunction perovskite solar cells (PVSCs). Despite various ETLs being designed for efficient PVSCs, there exists hardly any research on the effect of molecular stacking order on device performance. Herein, poly(ethylene-co-vinyl acetate) (EVA) is employed as the [6,6]-phenyl-C₆₁-butyric acid methyl ester (PC₆₁BM) solution additive. The strong binding energy between EVA with PC₆₁BM promotes the molecular stacking order of ETLs, which alleviates the morphology inhomogeneity, possesses a matched energy level, blocks ion migration, and improves the water–oxygen barrier of perovskite devices. The blade-coated MAPbI₃-based PVSCs achieve a power conversion efficiency (PCE) of 19.32% with positive reproducibility and negligible hysteresis, as well as maintain 90% and 80% of the initial PCE after storage under inert and ambient conditions (52% humidity) for 1500 h without encapsulation. This strategy also improves the champion PCE of CsFAMA-based PVSCs to 20.33%. These findings demonstrate that the regulation of molecular stacking order is a valid approach to optimize interfacial charge-carrier recombination in PVSCs, which meet the demand for high-performance ETL in large-area PVSCs and improve the upscaling of the fabrication technology toward practical applications.

A multifunctional surface design with the dense, stable, and crystalline-like 1H,1H,2H,2H-perfluorodecanethiol array is developed and applied onto the perovskite film and metal electrode. This strategy is demonstrated to not only impart the passivation effect and hydrophobic feature but also to suppress lead leakage via a synergy effect. Consequently, it facilitates the realization of stable and eco-friendly perovskite solar cells.

Abstract

Environment-related degradation and lead leakage in perovskite solar cells have posed a big challenge for their commercialization. Here, design of superhydrophobic surfaces is demonstrated as an effective strategy toward these issues, in which thiol-functionalized perfluoroalkyl molecules are employed to chemically modify the lead halide perovskite film and metal electrode via a vapor-assisted self-assembly process. Due to the van der Waals forces, the generation of self-assembly monolayer prefers to pack in a dense way, resulting in the formation of a closest-packed, crystalline-like molecular array. This dense array is endowed with a low-surface-energy chemistry that can not only enhance the water and oxygen resistance of the completed device but also reduce the defect density on the perovskite surfaces. These merits eventually boost the efficiency of inverted perovskite solar cells up to 21.79% along with a substantially improved long-term stability. More importantly, the thiol-functionalized superhydrophobic array can immobilize most of the undercoordinated lead ions on the perovskite surfaces by metal-thiol coordination effect, which results in suppressing the lead leakage from the water-soluble lead halide perovskites. Therefore, an avenue is pointed out here to fabricate stable perovskite solar cells with reducing lead leakage, representing a substantial step toward practical applications.

Hybrid perovskite with unsaturated organoammoniums is demonstrated to be able to undergo solid-state polymerization without damaging the perovskite structure. The polymerized perovskite behaves like a polymer with enhanced stability and flexi bility. The lattice rigidity is also enhanced due to the polymerized covalent CC bonding. As a result, a stable and efficient polymerized perovskite light-emitting diode with an external quantum efficiency (EQE) of 23.2% is demonstrated.

Abstract

The intrinsic soft lattice nature of organometal halide perovskites (OHPs) makes them very tolerant to defects and ideal candidates for solution-processed optoelectronic devices. However, the soft lattice results in low stability towards external stresses such as heating and humidity, high density of phonons and strong electron–phonon coupling (EPC). Here, it is demonstrated that the OHPs with unsaturated 4-vinylbenzylammonium (VBA) as organoammonium cations can be polymerized without damaging the perovskite structure and its tolerance to defects. The polymerized perovskites show enhanced stability and flexibility compared to regular three-dimensional and two-dimensional (2D) perovskites. Furthermore, the polymerized 4-vinylbenzylammonium group improves perovskite lattice rigidity substantially, resulting in a reduced non-radiative recombination rate because of suppressed electron–phonon coupling, and enhanced carrier mobility because of suppressed phonon scattering. 2D polymerized perovskite light-emitting diodes (PeLEDs) with strong electroluminescence at room temperature, and quasi-2D PeLEDs with an external quantum efficiency (EQE) of 23.2% and enhanced operation stability are demonstrated. The work has opened a new way of enhancing the intrinsic stability and optoelectronic properties of OHPs.

Publication date: 15 December 2021

Source: Joule, Volume 5, Issue 12

Author(s): Yanxun Li, Jianwei Ding, Cheng Liang, Xuning Zhang, Jianqi Zhang, Devon S. Jakob, Boxin Wang, Xing Li, Hong Zhang, Lina Li, Yingguo Yang, Guangjie Zhang, Xiaoxian Zhang, Wenna Du, Xinfeng Liu, Yuan Zhang, Yong Zhang, Xiaoji Xu, Xiaohui Qiu, Huiqiong Zhou