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Engineering Multiphase Metal Halide Perovskites Thin Films for Stable and Efficient Solar Cells
摘要： The intrinsic instability of lead halide perovskite semiconductors in an ambient atmosphere is one of the most critical issues that impedes perovskite solar cell commercialization. To overcome it, the use of bulky organic spacers has emerged as a promising solution. The resulting perovskite thin films present complex morphologies, difficult to predict, which can directly affect the device efficiency. Here, by combining in-depth morphological and spectroscopic characterization, it is shown that both the ionic size and the relative concentration of the organic cation, drive the integration of bulky organic cations into the crystal unit cell and the thin film, inducing different perovskite phases and different vertical distribution, then causing a significant change in the final thin film morphology. Based on these studies, a fine-engineered perovskite is constructed by employing two different large cations, namely, ethyl ammonium and butyl ammonium. The first one takes part in the 3D perovskite phase formation, the second one works as a surface modifier by forming a passivating layer on top of the thin film. Together they lead to improved photovoltaic performance and device stability when tested in air under continuous illumination. These findings propose a general approach to achieve reliability in perovskite-based optoelectronic devices.
关键词： stability,solar cells,metal halide perovskites,bulky cations,mixed dimension
更新于2025-09-16 10:30:52
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Low Rolla??Off Perovskite Quantum Dot Lighta??Emitting Diodes Achieved by Augmenting Hole Mobility
摘要： The external quantum efficiencies (EQEs) of perovskite quantum dot light-emitting diodes (QD-LEDs) are close to the out-coupling efficiency limitation. However, these high-performance QD-LEDs still suffer from a serious issue of efficiency roll-off at high current density. More injected carriers produce photons less efficiently, strongly suggesting the variation of ratio between radiative and non-radiative recombination. An approach is proposed to balance the carrier distribution and achieve high EQE at high current density. The average interdot distance between QDs is reduced and this facilitates carrier transport in QD films and thus electrons and holes have a balanced distribution in QD layers. Such encouraging results augment the proportion of radiative recombination, make devices with peak EQE of 12.7%, and present a great device performance at high current density with an EQE roll-off of 11% at 500 mA cm?2 (the lowest roll-off known so far) where the EQE is still over 11%.
关键词： perovskites,quantum dots,light-emitting diodes,Auger processes
更新于2025-09-16 10:30:52
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Chiral Reduced-Dimensional Perovskite for Efficient Flexible Circularly Polarized Light Photodetector
摘要： Advancements in exploring new chiral perovskites are highly demanded to improve the circular polarized light (CPL) detection efficiency to date. Reduced-dimensional (quasi-2D) perovskites thus emerged as the most promising candidates due to its appealing characteristics. We herein reported new chiral quasi-2D perovskite single crystals (SCs) synthesis, and investigate their CPL detecting capability for the first time. We proved quasi-2D chiral perovskites, [(R)-β-MPA]2MAPb2I7 ((R)-β-MPA = (R)-(+)-β-methylphenethylamine, MA = methylammonium), do possess intrinsic chirality and have the capability to distinguish different polarization states of CPL photons. Corresponding quasi-2D perovskite SCs CPL photodetector exhibit excellent detection performance. In particular, our device responsivity is almost one order of magnitude higher than the best reported 2D perovskite CPL detectors to date. On this basis, we carefully modulate the film’s crystallization dynamics to facilitate its carrier transport. We prove that parallelly oriented perovskite films with homogeneous energy landscape are crucial to maximize the device’s carrier collection efficiency. The obtained responsivity and linear dynamic range (LDR) of this flexible chiral quasi-2D perovskite thin-film photodetector are comparable with the best reported results to date. The photodetector also exhibits superior mechanical flexibility and durability, representing one of the most sensitive and robust CPL photodetector to date.
关键词： circular polarized light,photodetector,reduced-dimensional perovskites,chiral perovskite,crystallization dynamics
更新于2025-09-16 10:30:52
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Trap States, Electric Fields, and Phase Segregation in Mixeda??Halide Perovskite Photovoltaic Devices
摘要： Mixed-halide perovskites are essential for use in all-perovskite or perovskite–silicon tandem solar cells due to their tunable bandgap. However, trap states and halide segregation currently present the two main challenges for efficient mixed-halide perovskite technologies. Here photoluminescence techniques are used to study trap states and halide segregation in full mixed-halide perovskite photovoltaic devices. This work identifies three distinct defect species in the perovskite material: a charged, mobile defect that traps charge-carriers in the perovskite, a charge-neutral defect that induces halide segregation, and a charged, mobile defect that screens the perovskite from external electric fields. These three defects are proposed to be MA+ interstitials, crystal distortions, and halide vacancies and/or interstitials, respectively. Finally, external quantum efficiency measurements show that photoexcited charge-carriers can be extracted from the iodide-rich low-bandgap regions of the phase-segregated perovskite formed under illumination, suggesting the existence of charge-carrier percolation pathways through grain boundaries where phase-segregation may occur.
关键词： halide segregation,perovskites,electric fields,trap states,photovoltaic devices
更新于2025-09-16 10:30:52
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Sensitive Terahertz Free Space Modulator Using CsPbBr3 Perovskite Quantum Dotsa??Embedded Metamaterial
摘要： We have demonstrated a method for active modulating terahertz wave using CsPbBr3 perovskite quantum dots (QDs)–embedded double-C metallic metamaterial unit cells. The resonance response frequency of the proposed CsPbBr3 perovskite QDs-embedded metamaterial can be tuned by varying the external applied photoexcitation intensity. By doing so, we measured the dynamic terahertz wave transmission modulation and demonstrate tuning of the terahertz wave resonant response based on the optical pump fluences. The modulation speed and depth of the modulator are 5 MHz and 88.3%, respectively. Our results indicate the importance of manipulating the terahertz wave for future wireless communication.
关键词： Terahertz modulation,CsPbBr3 perovskites quantum dots,Terahertz wave
更新于2025-09-16 10:30:52
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Wavelength-selective degradation of perovskite-based solar cells
摘要： The J-V characteristics of perovskite-based solar cells were measured under selective irradiation in three different domains of the solar spectrum: blue, red and near infrared (NIR). It was found out that even in the inert atmosphere a long-term exposure to both blue and red sources leads to formation of PbI2, but in the former case the degradation of hybrid perovskite is greater due to further photolysis of PbI2. Consequently, the cell performance under illumination with the red light decreases insignificantly. The NIR irradiance improves the perovskite stoichiometry so that the photovoltaic parameters of the cells increase with the exposure time. These features are undistinguishable under continuous sunlight. Therefore, the wavelength-selective J-V measurements piece together the jigsaw of light-induced degradation of hybrid perovskites and open new strategies for the improvement of the device stability.
关键词： illumination range,solar cells,morphology,perovskites
更新于2025-09-12 10:27:22
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Charge Injection from Excited Cs2AgBiBr6 Quantum Dots into Semiconductor Oxides
摘要： Lead-free double perovskites such as Cs2AgBiBr6 are gaining attention because of their environmental friendliness compared to the lead halide perovskites. In order to establish their photoactivity, we have probed the excited state behavior of Cs2AgBiBr6 nanocrystals and charge injection from their excited state into different metal oxides (TiO2, ZnO). The electron transfer rate constants determined from ultrafast transient absorption spectroscopy were in the range of 1.2–5.2 × 1010 s-1. Under steady state photolysis (ambient conditions) the electrons injected into TiO2 are scavenged by atmospheric oxygen, leaving behind holes which accumulate within the quantum dots (QDs). These accumulated holes further induce oxidation of QDs, resulting in the overall photodegradation of perovskite film. Annealed films of Cs2AgBiBr6 nanocrystals, when employed as an active layer in solar cell, delivered photocurrent under visible light excitation.
关键词： Metal oxides,Quantum dots,Photodegradation,Charge injection,Cs2AgBiBr6,Solar cells,Lead-free double perovskites
更新于2025-09-12 10:27:22
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Efficient sky-blue perovskite light-emitting diodes via photoluminescence enhancement
摘要： The efficiencies of green and red perovskite light-emitting diodes (PeLEDs) have been increased close to their theoretical upper limit, while the efficiency of blue PeLEDs is lagging far behind. Here we report enhancing the efficiency of sky-blue PeLEDs by overcoming a major hurdle of low photoluminescence quantum efficiency in wide-bandgap perovskites. Blending phenylethylammonium chloride into cesium lead halide perovskites yields a mixture of two-dimensional and three-dimensional perovskites, which enhances photoluminescence quantum efficiency from 1.1% to 19.8%. Adding yttrium (III) chloride into the mixture further enhances photoluminescence quantum efficiency to 49.7%. Yttrium is found to incorporate into the three-dimensional perovskite grain, while it is still rich at grain boundaries and surfaces. The yttrium on grain surface increases the bandgap of grain shell, which confines the charge carriers inside grains for efficient radiative recombination. Record efficiencies of 11.0% and 4.8% were obtained in sky-blue and blue PeLEDs, respectively.
关键词： radiative recombination,perovskite light-emitting diodes,yttrium (III) chloride,photoluminescence quantum efficiency,wide-bandgap perovskites
更新于2025-09-12 10:27:22
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Highly oriented perovskites for efficient light-emitting diodes with balanced charge transport
摘要： Ruddlesden-Popper (RP) perovskites have attracted interests due to high performance in perovskite light-emitting diodes (PeLEDs). However, the insulating organic spacers decrease carrier mobility, and increase charge accumulation and non-radiative recombination losses, which significantly undermine device performance. Herein, by blending NH3I(CH2)8NH3I (ODA) and INH3(CH2)2O(CH2)2O(CH2)2NH3I (EDBE) large organic spacers into the precursor solution, we achieve preferential orientation of perovskite crystals perpendicular to the substrate with conductive channels across the two injecting electrodes. Consequently, effective charge injection and balanced charge transport are achieved, which is beneficial to increase radiation recombination. A low turn-on voltage of 1.4 V is achieved for mixture-1.5 perovskite (ODA: EDBE=3:2, molar ratio) PeLEDs, and a maximum external quantum efficiency increases to 5.8% (EL peak ≈766 nm) at 2.0 V with a current density of 6.05 mA cm?2 compared to that of the pure ODA (2.4%) and EDBE (1.1%) devices. The findings may spur new developments in charge injection and electron-hole balance for realizing efficient PeLEDs.
关键词： Perovskites,Ruddlesden-Popper,Organic spacers,Light-emitting diodes,Charge transport
更新于2025-09-12 10:27:22
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Enhanced Moisture Stability by Butyldimethylsulfonium Cation in Perovskite Solar Cells
摘要： Many organic cations in halide perovskites have been studied for their application in perovskite solar cells (PSCs). Most organic cations in PSCs are based on the protic nitrogen cores, which are susceptible to deprotonation. Here, a new candidate of fully alkylated sulfonium cation (butyldimethylsulfonium; BDMS) is designed and successfully assembled into PSCs with the aim of increasing humidity stability. The BDMS-based perovskites retain the structural and optical features of pristine perovskite, which results in the comparable photovoltaic performance. However, the fully alkylated aprotic nature of BDMS shows a much more pronounced effect on the increase in humidity stability, which emphasizes a generic electronic difference between protic ammonium and aprotic sulfonium cation. The current results would pave a new way to explore cations for the development of promising PSCs.
关键词： perovskites solar cells,humidity stability,density functional theory (DFT),butylammonium iodide,butyldimethylsulfonium iodide
更新于2025-09-12 10:27:22