Multifunctional Conjugated Molecular Additives for Highly Efficient Perovskite Light-Emitting Diodes

Plasmon-enhanced exciton relocalization in quasi-2D perovskites for low-threshold room-temperature plasmonic lasing

Room-temperature nanolasers are crucial for advancing optical communication and photonic quantum technologies due to their capability to generate coherent light at a subwavelength scale. However, their development is constrained by challenges such as insufficient gain, material instability, and high lasing thresholds. By integrating quasi-two-dimensional (quasi-2D) perovskites with high-Q plasmonic nanostructures, we demonstrate a stable, wavelength-tunable, single-mode laser operating at room temperature. This device leverages a unique exciton relocalization effect in quasi-2D Ruddlesden-Popper perovskites with additives, substantially enhancing optical gain and improving stability. When coupled with a waveguide-hybridized surface lattice resonance mode, the enhanced light-matter interaction facilitates single-mode lasing with a notably low threshold of 0.9 millijoules per square centimeter. In addition, the device achieves robust lasing performance with extended operational stability (1.8 × 106 excitation pulses). These results provide a scalable, low-cost, and energy-efficient platform for nanolasing, with potential applications in next-generation photonic technologies, including light detection and ranging, sensing, optical communication, and computation.

Efficient and stable blue perovskite light-emitting diodes enabled by the synergistic incorporation of dual additives

Perovskite materials have garnered significant attention in the field of light-emitting diodes (LEDs) due to their low cost, solution processing, straightforward fabrication, tunable emission wavelengths, narrow emission linewidths, and high photoluminescence quantum yield. However, blue perovskite light-emitting diodes (PeLEDs) currently face challenges of low efficiency and poor stability, which hinder their application in full-color display technology. It is understood that the quality of the perovskite film is considered a key factor affecting the performance of PeLEDs. To achieve high-quality perovskite films and high-performance PeLEDs, benzoic acid potassium (BAP) and guanidinium chloride (GACl) were employed as dual additives in the precursor solution of a quasi-two-dimensional perovskite (PEA2Csn-1PbnX3n+1). By utilizing the coordination of BA- from BAP with uncoordinated Pb2+ and the formation of hydrogen bonds between GA+ from GACl and halide ions, the perovskite surface defects are effectively passivated, along with the inhibition of the migration of halide ions. This approach reduces non-radiative recombination and enhances the spectral stability of perovskite films. By fine-tuning the concentrations of BAP and GACl, optimal PeLEDs are achieved at a BAP concentration of 3% and a GACl concentration of 10%, with the spectrum stabilized at 476 nm and a maximum external quantum efficiency (EQEmax) of 4.47%, which is 2.54 times that of the control device (EQEmax of 1.76%). The findings in this study provide a new approach for the fabrication of highly efficient and spectrally stable blue PeLEDs.

Multiple Chemical Interactions in Additive Engineering of Perovskite for Enhanced Efficiency and Stability of Pure Blue Light-Emitting Diodes

Additive engineering is extensively employed in perovskite light-emitting diodes (PeLEDs) to enhance the device performance. However, the effectiveness of additives is restricted, as they generally interact with only one or two components within the perovskite structure. Consequently, these additives are unable to fulfill the comprehensive functional requirements imposed by perovskite light-emitting materials. In this work, we successfully designed and synthesized a multifunctional additive of N-(perfluorophenyl)-P,P-diphenylphosphinic amide (PFNPO) via a one-step synthesis approach. Multiple chemical interactions can be provided between PFNPO and different perovskite components, thereby effectively modulating quasi-two-dimensional (quasi-2D) perovskite crystallization, passivating coordination-unsaturated Pb defects, and suppressing halide ion migration simultaneously. Based on these synergistic effects, the incorporation of PFNPO in pure blue quasi-2D PeLEDs resulted in a significant enhancement in external quantum efficiency from 1.83 to 4.26%, an operational lifetime that was extended by more than 3-fold, and improved spectral stability at 466 nm.

Surficial Homogenic Effect Enables Highly Stable Deep-Blue Perovskite Light-Emitting Diodes

The device performance of deep-blue perovskite light-emitting diodes (PeLEDs) is primarily constrained by low external quantum efficiency (EQE) especially poor operational stability. Herein, we develop a facile strategy to improve deep-blue emission through rational interface engineering. We innovatively reported the novel electron transport material, 4,6-Tris(4-(diphenylphosphoryl)phenyl)-1,3,5-triazine (P-POT2T), and utilized a sequential wet-dry deposition method to form the homogenic gradient interface between electron transport layer (ETL) and perovskite surface. Unlike previous reports that achieved carrier injection balance by inserting new interlayers, our strategy not only passivated uncoordinated Pb2+ in the perovskite via P=O functional groups but also reduced interfacial carrier recombination without introducing new interfaces. Additionally, this strategy enhanced the interface contact between the perovskite and ETL, significantly boosting device stability. Consequently, the fabricated deep-blue PeLEDs delivered an EQE exceeding 5 % (@ 460 nm) with an exceptional halftime extended to 31.3 minutes. This straightforward approach offers a new strategy to realize highly efficient especially stable PeLEDs.

Modulation of Charge Transport Layer for Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (Pero-LEDs) have garnered significant attention due to their exceptional emission characteristics, including narrow full width at half maximum, high color purity, and tunable emission colors. Recent efficiency and operational stability advancements have positioned Pero-LEDs as a promising next-generation display technology. Extensive research and review articles on the compositional engineering and defect passivation of perovskite layers have substantially contributed to the development of multi-color and high-efficiency Pero-LEDs. However, the crucial aspect of charge transport layer (CTL) modulation in Pero-LEDs remains relatively underexplored. CTL modulation not only impacts the charge carrier transport efficiency and injection balance but also plays a critical role in passivating the perovskite surface, blocking ion migration, enhancing perovskite crystallinity, and improving light extraction efficiency. Therefore, optimizing CTLs is pivotal for further enhancing Pero-LED performance. Herein, this review discusses the roles of CTLs in Pero-LEDs and categorizes both reported and potential CTL materials. Then, various CTL optimization strategies are presented, alongside an analysis of the selection criteria for CTLs in high-performance Pero-LEDs. Finally, a summary and outlook on the potential of CTL modulation to further advance Pero-LED performances are provided.

Supersaturated Antisolvent-Assisted Crystallization for Highly Efficient Inorganic Perovskite Light-Emitting Diodes

We introduced a strategy to form nanocrystalline CsPbBr3 perovskite films with high luminescence and stability, inhibiting crystal growth using a CsBr supersaturated antisolvent during the antisolvent-assisted crystallization process. We devised this strategy because the supersaturated antisolvent has a higher CsBr concentration over its solubility limit in the saturated antisolvent and consequently will form the smaller perovskite nanocrystalline grains due to the quick precipitation of the CsBr. Here, the CsBr is chosen as a model inorganic antisolvent additive for a crystal growth inhibitor and a passivator. Consequently, we have achieved a nanocrystalline CsPbBr3 film with an average grain size of ∼39 nm by the CsBr supersaturated antisolvent-assisted crystallization process, which is about 41% smaller than the average grain size of the control sample. Hence, the perovskite thin film exhibited a much higher photoluminescence quantum yield than the control film. The maximum current efficiency (CEmax) and the maximum external quantum efficiency (EQEmax) of the corresponding CsPbBr3 perovskite light-emitting diodes (PeLEDs) were approximately twice higher (CEmax of 94.64 cd A-1 and EQEmax of 22.93%) than those of the control device. Simultaneously, the inclusion of CsBr additives played a multifunctional role in diminishing the leakage current of PeLEDs and enhancing their operational lifetime.

Supramolecular Polyurethane "Ligaments" Enabling Room-Temperature Self-Healing Flexible Perovskite Solar Cells and Mini-Modules

Flexible perovskite solar cells (F-PSCs) have emerged as promising alternatives to conventional silicon solar cells for applications in portable and wearable electronics. However, the mechanical stability of inherently brittle perovskite, due to residual lattice stress and ductile fracture formation, poses significant challenges to the long-term photovoltaic performance and device lifetime. In this paper, to address this issue, a dynamic "ligament" composed of supramolecular poly(dimethylsiloxane) polyurethane (DSSP-PPU) is introduced into the grain boundaries of the PSCs, facilitating the release of residual stress and softening of the grain boundaries. Remarkably, this dynamic "ligament" exhibits excellent self-healing properties and enables the healing of cracks in perovskite films at room temperature. The obtained PSCs have achieved power conversion efficiencies of 23.73% and 22.24% for rigid substrates and flexible substrates, respectively, also 17.32% for flexible mini-modules. Notably, the F-PSCs retain nearly 80% of their initial efficiency even after subjecting the F-PSCs to 8000 bending cycles (r = 2 mm), which can further recover to almost 90% of the initial efficiency through the self-healing process. This remarkable improvement in device stability and longevity holds great promise for extending the overall lifetime of F-PSCs.

Investigation of the Role of K2SO4 Electrolyte in Hole Transport Layer for Efficient Quasi-2D Perovskite Light-Emitting Diodes

Quasi-two-dimensional (2D) perovskite light-emitting diodes are promising light sources for color display and lighting. However, poor carrier injection and transport between the bottom hole transport layer (HTL) and perovskite limit the device performance. Here we demonstrate a simple and effective way to modify the HTL for enhancing the performance of perovskite light-emitting diodes (PeLEDs). An electrolyte K2SO4 is used to mix with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the hole transport layer. The K+ doping helped the quasi-2D perovskite phases grow vertically along the interface of the PEDOT:PSS, fine-modulate the phase distribution, and simultaneously reduce the defect density of quasi-2D perovskites. It also significantly reduced the exciton quenching and injection barrier at PEDOT:PSS and quasi-2D perovskite interface. The optimized green PeLEDs with the K2SO4 doped PEDOT:PSS HTL showed a maximum luminance of 17185 cd/m2 which is almost 4.7 times brighter than the control one, with a maximum external quantum efficiency of 18.64%.

Anionic Conjugated Polyelectrolyte as a Semiconducting Additive for Efficient and Stable Perovskite Solar Cells

Perovskite defects are a major hurdle in the efficiency and stability of perovskite solar cells (PSCs). While various defect passivation materials have been explored, most are insulators that hinder charge transport. This study investigates the potential of two different π-conjugated polyelectrolytes (CPEs), MPS2-TEA and PCPDTBT2-TMA, as semiconducting additives in PSCs. The CPEs differ in electrical conductivity, offering a unique approach to bridge defect mitigation and charge carrier transport. Unlike previous uses of CPEs mainly as interlayers or charge transport layers, we explore their direct effect on defect passivation within a perovskite layer. Secondary ion microscopy reveals the even distribution of CPEs within the perovskite layer and their efficient defect passivation potential is studied through various spectroscopic analyses. Comparing MPS2-TEA and PCPDTBT2-TMA, we find MPS2-TEA to be superior in defect passivation. The highly conductive nature of PCPDTBT2-TMA due to self-doping diminishes its defect passivation ability. The negative sulfonate groups in the side chains of PCPDTBT2-TMA stabilize polarons, reducing defect passivation capability. Finally, the PSCs with MPS2-TEA achieve remarkable power conversion efficiencies (PCEs) of 22.7% for 0.135 cm2 and 20.0% for large-area (1 cm2) cells. Furthermore, the device with MPS2-TEA maintained over 87.3% of initial PCE after 960 h at continuous 1-sun illumination and 89% of PCE after 850 h at 85 °C in a nitrogen glovebox without encapsulation. This highlights CPEs as promising defect passivation additives, unlocking potential for improved efficiency and stability not only in PSCs but also in wider applications.