Quantum Stability Research Articles

Passivation of Surface Defects by X-type Short-Chain Ligands for High Quantum Yield and Stable CsPbX3 Quantum Dots Synthesis and Application in WLEDs

All-inorganic CsPbX3 perovskite quantum dots have excellent optoelectronic properties and are excellent candidates for optoelectronic applications. However, the surface ligands (oleyl ammonium, oleic acid) commonly used in traditional inorganic perovskite quantum dots easily fall off from the quantum dots and their protective power is relatively weak, resulting in poor quantum yield and stability of the quantum dots, limiting their application. In this paper, we introduce an X-type short-chain ligand (DDEAB) passivation strategy to enhance the optoelectronic properties of CsPbX3 quantum dots through a facile room-temperature synthesis method and the strong affinity of X-type ligands for surface atoms. The results of TRPL and X-ray photoelectron spectroscopy showed longer lifetime and stronger surface affinity. This result confirms that didecyldimethylammonium bromide (DDEAB) has better binding to CsPbBr3 QDs and can effectively reduce surface defects and improve quantum yield. As a result, the introduction of short-chain ligands can more effectively passivate the surface halogen defects of CsPbX3 QDs, achieving high quantum yield (>90%) and long-term storage environmental stability. In addition, DDEAB-passivated CsPbBr3 QDs have been successfully applied in white light emitting diodes (WLEDs) with wider color gamut (123%), and good EL stability compared to NTSC TV color standard. Our proposed short-chain ligand DDEAB passivation strategy may provide a reference guideline for the preparation of quantum dots and photovoltaic devices with high photoluminescence and environmental stability.

Activating Electroluminescence of Charged Naphthalene Diimide Complexes Directly Adsorbed on a Metal Substrate.

Electroluminescence from single molecules adsorbed on a conducting surface imposes conflicting demands for the molecule-electrode coupling. To conduct electrons, the molecular orbitals need to be hybridized with the electrodes. To emit light, they need to be decoupled from the electrodes to prevent fluorescence quenching. Here, we show that fully quenched 2,6-core-substituted naphthalene diimide derivative in a self-assembled monolayer directly deposited on a Au(111) surface can be activated with the tip of a scanning tunneling microscope to decouple the relevant frontier orbitals from the metallic substrate. In this way, individual molecules can be driven from a strongly hybridized state with quenched luminescence to a light-emitting state. The emission performance compares in terms of quantum efficiency, stability, and reproducibility to that of single molecules deposited on thin insulating layers. Quantum chemical calculations suggest that the emitted light originates from the singly charged cationic pair of the molecules.

Plasmon-enhanced nano-photosensitizers: game-changers in photodynamic therapy of cancers.

Plasmonic nanostructures can be used to tackle the shortcomings of conventional photosensitizers in photodynamic therapy (PDT) of cancers, including their low reactive oxygen species (ROS) quantum yield, stability, and targetability. However, the positive role of plasmonic nanostructures is not limited to their ability for ROS generation or singlet oxygen formation. The main advantage of plasmonic nanostructures relies on the collective oscillation of free electrons, the so-called surface plasmon resonance (SPR), which can trigger plenty of optical phenomena in their near-field. Surface plasmon resonance is highly dependent on the morphology, size, and composition of the plasmonic nanostructure, which can give one the ability to control the wavelength of light-matter interaction, which is highly desirable in PDT applications. This review has focused on the conjugation of plasmonic nanostructures with organic compounds, biological compounds, ceramic nanoparticles, polymeric nanoparticles, metal-organic frameworks (MOFs), and magnetic nanoparticles from a mechanistic point of view. Hybridization of plasmonic nanoparticles would enable plenty of optical mechanisms beneficial for the PDT process that has been extensively discussed by presenting the most recent efforts in each category. This review can be a useful guideline for researchers working on enhancing the efficiency of the PDT process and those interested in plasmon-enhanced phenomena by emphasizing the underlying mechanisms.

Near-Unity Photoluminescence Quantum Yield of Green-Emitting Graded-Alloy Core/Shell Giant Quantum Dots by z-Type Ligand Passivation for Display Applications

As-synthesized, green-emitting graded-alloy core/shell “giant” quantum dots have outstanding properties that can be utilized for different optoelectronic applications. But often, defects arise upon nonuniform growth of the shell. These surface defects affect the photoluminescence quantum yield (PLQY), lifetime, and stability of the green-emitting graded-alloy core/shell “giant” quantum dots. So, to overcome these surface traps, the graded-alloy core/shell g-QDs were passivated with z-type ligands (ZnCl2, CdCl2, and MgCl2). The change in the PLQY, lifetime, and photoluminescence emission confirmed that the z-type ligands are passivating the trap states of g-QDs by bonding with an unsaturated chalcogenide atom on the surface, and this was confirmed by X-ray photoelectron spectroscopy. All three cases (treated with ZnCl2, CdCl2, and MgCl2) showed outstanding enhancement in the photoluminescence quantum yield. Fascinatingly, the ZnCl2-treated g-QDs showed maximum enhancement in the PLQY from 62% to unity. Furthermore, the photostability test was performed under continuous UV-light irradiation for 24 h, which clearly showed superior photostability. Moreover, the temperature-dependent stability of untreated and treated g-QDs was studied from 10 to 90 °C. Furthermore, the green-emitting down-converted LED was fabricated by utilizing ZnCl2-treated g-QDs, which show great potential for display application.

Highly efficient ZnO photocatalytic foam reactors for micropollutant degradation

The efficient removal of organic micropollutants, pharmaceuticals, pesticides, drugs, and others, remains an unsolved challenge in water treatment. Although photocatalysis has proven highly effective at degrading these substances, its large-scale implementation has been so far hampered by technical and economic concerns. This work describes the development and characterization of novel highly efficient, self-supporting photocatalytic ZnO foams for the degradation of organic micropollutants. A systematic investigation of flow rate, catalyst length and stability under both recirculating and single-pass conditions was conducted using carbamazepine as a UV-recalcitrant model pollutant. Under recirculation, 95 % degradation was achieved with photocatalyst quantum yield of 1.2 × 10−3 and electrical energy per order (EEO) as low as 24 kWh m−3, values outperforming current technology, slurry and immobilised systems. For single-pass tests, complete degradation was achieved in 30 min, with the quantum yield increasing to 6.3 × 10−3, and an EEO of 36 kWh m−3. These values also outperform those for slurries, immobilised and other foam photocatalyst reported in the literature under similar conditions. The low energy consumption of these newly developed photocatalytic foams, combined with their high quantum yield and stability, provides a realistic path towards practical implementation of photocatalytic processes in water treatment, addressing the limitations of existing slurry and immobilised photocatalytic technology.

Enhanced amplified spontaneous emission of CsPbBr3 quantum dots via gold nanorods-induced localized surface plasmon resonance

Incorporating metallic nanostructures into a cesium lead halide [CsPbX3 (X = Cl, Br, I)] perovskite system has attracted considerable attention for improving the performance of amplified spontaneous emission (ASE) and lasing. However, the ASE/lasing threshold is normally quite high since the photophysical properties of pristine CsPbX3 quantum dots (QDs) are limited and the traditionally utilized metal nanoparticles suffer from a weak localized surface plasmon resonance within a narrow spectral range. Herein, a configuration of a silica coated CsPbBr3 QDs (CsPbBr3@SiO2 QDs) film incorporated with the deposition of gold nanorods (AuNRs) underneath has been proposed for high-performance ASE. In this configuration, SiO2 coating not only serves as an insulation layer to avoid the large Ohmic loss between CsPbBr3 and Au but also contributes to improved photoluminescence quantum yield and stability against water, heat, and ultraviolet light compared to the counterparts of pristine CsPbBr3 QDs. As a result, the fabricated CsPbBr3@SiO2-AuNRs hybrid film yields a low-threshold ASE (23.6 μJ/cm2) with excellent photostability owing to efficient exciton–plasmon coupling effect, which is only 23% of the pristine CsPbBr3 QDs film (102 μJ/cm2). The demonstration of metallic NRs coupled perovskite QDs not only provides a strategy for realizing strong light–matter interactions but also paves the way for improving the performance of perovskite-based optoelectronic devices.

Opportunities and challenges in CsPbX3@Glasses@Film with High Quality for LCD by Process Optimization towards commercialization

Although backlight display screens based on CdSe quantum dots (QDs) have basically solved the remaining problem of small display gamut, its high preparation cost limits its commercial development. In contrast, perovskite nanocrystals (NCs) with narrow band emission, simple preparation and low cost have made leaps and bounds in next-generation backlit displays luminescent material. However, the instabilities are the main issues to solve before we can apply these materials in modern displays. Researchers have precipitated perovskite NCs in inorganic glass substrates and compounded them with PDMS films for backlighting, but the important factors for commercialization have been ignored: Long-term stability under strong blue light irradiation and preparation cost. In this work, a unique melt-water quenching method combined with composition control was applied to prepare a series of glass powder. The optimal photoluminescence (PL) emission and color coordinates in the color coordinates of glasses powder were elaborately regulated by heat treatment temperature control and the introduction of rare earth Tb. Moreover, the passivation of the glass powder surface through special water treatment greatly improves its stability under long time blue light exposure. After irradiation under 20000 cd/m2 blue light (460 nm) for 500 h, the PL intensity retention rate reaches 85% of commercial CdSe film. The red and green-emitting NCs glasses powder with high photoluminescence quantum yield (PLQY) and stability were combined with PET, PS and PDMS to form a composite film, afterwards, combined with Liquid crystal display (LCD)module shows a fuller color image. Finally, after comparison, PS film was demonstrated to be the most suitable choice for commercialization backlighting.

(Digital Presentation) Fine Nitride Phosphors for Mini-LED Backlights

Mini-LED backlights, combining color conversion materials with blue Mini-LED chips, promise traditional liquid crystal displays (LCDs) with higher luminance, better contrast and wider color gamut. As color conversion materials, Cd- or Pb-based quantum dots are usually toxic and unstable, and commercially available inorganic phosphors are quite stable and cheap, but they have a large size due to their synthesis at high temperature, and their quantum efficiency and reliability are size dependent. To make inorganic phosphors to be well combined with Mini-LED chips (usually 100 x100 μm in size) in the emerging Mini-LED backlights, the particle size of the phosphors needs to be reduced to several micrometers or sub-micrometers while the quantum efficiency remains unchanged. In this work, we prepared fine nitride phosphors by treating commercially available phosphors, including CaAlSiN3:Eu2+ and (Sr, Ba)2Si5N8:Eu2+, with ball milling, centrifuging and acid washing. The particle size of phosphors can be easily controlled by the milling speed, and the phosphors with a size varying from 0.5 to 15 mm were thus obtained. The samples remained the comparable quantum efficiency with the original ones even when their particle size was reduced to 2 μm as they contained less surface defects after acid washing. We demonstrated that red-emitting Mini-LEDs can be fabricated by combining the red phosphors with blue Mini-LED chips, which show higher external quantum efficiency, luminance and stability than those made by using quantum dots. It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work, and they have great potentials for use in Mini-LED displays.

Topological and quantum stability of low-dimensional crystalline lattices with multiple nonequivalent sublattices* *Dedicated to the memory of our close friend, fellow colleague, former student (PA) and teacher (AK) Prof. A A Kuzubov (1974–2016).

The terms of topological and quantum stabilities of low-dimensional crystalline carbon lattices with multiple non-equivalent sublattices are coined using theoretical analysis, multilevel simulations, and available experimental structural data. It is demonstrated that complex low-dimensional lattices are prone to periodicity breakdown caused by structural deformations generated by linear periodic boundary conditions (PBC). To impose PBC mandatory limitations for complex low-dimensional lattices, the topology conservation theorem (TCT) is introduced, formulated and proved. It is shown that the lack of perfect filling of planar 2D crystalline space by structural units may cause the formation of (i) structure waves of either variable or constant wavelength; (ii) nanotubes or rolls; (iii) saddle structures; (iv) aperiodic ensembles of irregular asymmetric atomic clusters. In some cases the lattice can be stabilized by aromatic resonance, correlation effects, or van-der-Waals interactions. The effect of quantum instability and periodicity breakdown of infinite structural waves is studied using quasiparticle approach. It is found that both perfect finite-sized, or stabilized structural waves can exist and can be synthesized. It is shown that for low-dimensional lattices prone to breakdown of translation invariance (TI), complete active space of normal coordinates cannot be reduced to a subspace of TI normal coordinates. As a result, constrained TI subspace structural minimization may artificially return a regular point at the potential energy surface as either a global/local minimum/maximum. It is proved that for such lattices, phonon dispersion cannot be used as solid and final proof of either stability or metastability. It is shown that ab initio molecular dynamics (MD) PBC Nosé–Hoover thermostat algorithm constrains the linear dimensions of the periodic slabs in MD box preventing their thermostated equilibration. Based on rigorous TCT analysis, a flowchart algorithm for structural analysis of low-dimensional crystals is proposed and proved to be a powerful tool for theoretical design of advanced complex nanomaterials.

Highly efficient green emission Cs4PbBr6 quantum dots with stable water endurance.

To date, quantum dots (QDs) based on perovskite materials with high photoluminescence quantum yield (PLQY) and stability have rarely been reported. In this work, Cs4PbBr6 QDs glass ceramic with high PLQY and water stability is obtained, and the research results confirm that the strong green emission originates from the trapping of free excitons by internal Br vacancies. The rise of Br vacancies and the spontaneous growth of multi-morphology Cs4PbBr6 QDs under the influence of air humidity increase the PLQY to 89.62%. Compared with pure QDs, the Cs4PbBr6 QDs maintain high-intensity luminescence after being immersed in water for up to 150 days. In short, this paper puts forward a new, to the best of our knowledge, and valuable perspective for investigating the luminescence of Cs4PbBr6 QDs glass ceramic derived from related work.

High quantum yield carbon quantum dots as selective fluorescent turn-off probes for dual detection of Fe2+/Fe3+ ions

Carbon quantum dots (CQDs) are fluorescent nanoparticles that have great potential for use as nontoxic fluorescent probes. However, synthesizing CQDs with high photoluminescence quantum yield (QY) in a rapid and facile way from commonly available and low-cost reagents is still challenging. In this work, Tween®80 was used as a surface passivation agent along with citric acid/urea in a one-step microwave procedure to make extremely blue luminous nitrogen doped CQDs. When excited at 350 nm, these CQDs had a fluorescent quantum yield of 75.5 %. The significant high quantum yield and stability of these CQDs are attributed to the high aromatic sp2 domain size within the CQD core and improved carbon and oxygen functional groups at the CQDs surface. We employed the CQDs as a fluorescent probe to detect Fe2+ and Fe3+ ions and could establish a linear relationship between photoluminescence quenching efficiency (F0-F/F0) and ion concentration with a detection limit of 6.5 µM and 2.5 µM for Fe2+ and Fe3+, respectively. Our studies suggest that the highly selective detection of iron ions is a result of partial transfers of excited electrons from the CQDs to the d orbital of the iron ions, instead of contributing to radiative relaxation that induces photoluminescence quenching of the CQDs. Other reported carbon dots for this application have a substantially lower quantum yield and only detect Fe3+ ions. Therefore, our CQDs have considerable benefits over similar probes. Subsequent research may adapt them to other areas due to the high quantum yield and stability.

Expanding the absorption and photoresponse of 1D lead-halide perovskites via ultrafast charge transfer.

Low-dimensional metal halide perovskites are attracting extensive attention due to their enhanced quantum confinement and stability compared to three-dimensional perovskites. However, low dimensional connectivity in the inorganic frameworks leads to strongly bounded excitons with limited absorption properties, which impedes their application in photovoltaic devices. Here, we show that, by incorporating a strong electron accepting methylviologen cation, charge transfer (CT) at the organic/inorganic interface can effectively tune the optical properties in one-dimensional (1D) lead-halide perovskites. Both 1D MVPb2I6 and MVPb2Br6 display expanded absorption and photoresponse activity compared to CT inactive cations. The photoinduced CT process in MVPb2I6 was further characterized by transient absorption spectroscopy, which shows an ultrafast CT process within 1ps, generating charge separated states. Our work unveils the interesting photophysics of these unconventional 1D perovskites with functional organic chromophores.

Ratiometric fluorescence immunoassay of SARS-CoV-2 nucleocapsid protein via Si-FITC nanoprobe-based inner filter effect.

The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has necessitated rapid, easy-to-use, and accurate diagnostic methods to monitor the virus infection. Herein, a ratiometric fluorescence enzyme-linked immunosorbent assay (ELISA) was developed using Si-fluorescein isothiocyanate nanoparticles (FITC NPs) for detecting SARS-CoV-2 nucleocapsid (N) protein. Si-FITC NPs were prepared by a one-pot hydrothermal method using 3-aminopropyl triethoxysilane (APTES)-FITC as the Si source. This method did not need post-modification and avoided the reduction in quantum yield and stability. The p-nitrophenyl (pNP) produced by the alkaline phosphatase (ALP)-mediated hydrolysis of p-nitrophenyl phosphate (pNPP) could quench Si fluorescence in Si-FITC NPs via the inner filter effect. In ELISA, an immunocomplex was formed by the recognition of capture antibody/N protein/reporter antibody. ALP-linked secondary antibody bound to the reporter antibody and induced pNPP hydrolysis to specifically quench Si fluorescence in Si-FITC NPs. The change in fluorescence intensity ratio could be used for detecting N protein, with a wide linearity range (0.01–10.0 and 50–300 ng/mL) and low detection limit (0.002 ng/mL). The concentration of spiked SARS-CoV-2 N protein could be determined accurately in human serum. Moreover, this proposed method can accurately distinguish coronavirus disease 2019 (COVID-19) and non-COVID-19 patient samples. Therefore, this simple, sensitive, and accurate method can be applied for the early diagnosis of SARS-CoV-2 virus infection.Electronic Supplementary MaterialSupplementary material (characterization of Si-FITC NPs (FTIR spectrum, XRD spectra, and synchronous fluorescence spectra); condition optimization of ALP response (fluorescence intensity ratio change); mechanism investigation of ALP response (fluorescence lifetime decay curves and UV—vis absorption spectra); detection of N protein using commercial ELISA Kit; analytical performance of assays for ALP detection or SARS-CoV-2 N protein detection; and determination results of SARS-CoV-2 N protein in human serum) is available in the online version of this article at 10.1007/s12274-022-4740-5.

Efficient and Stable Blue Light Emitting Diodes Based on CsPbBr3 Nanoplatelets with Surface Passivation by a Multifunctional Organic Sulfate

AbstractMetal halide perovskite nanocrystals (NCs) have emerged as highly promising light emitting materials for various applications, ranging from perovskite light‐emitting diodes (PeLEDs) to lasers and radiation detectors. While remarkable progress has been achieved in highly efficient and stable green, red, and infrared perovskite NCs, obtaining efficient and stable blue‐emitting perovskite NCs remains a great challenge. Here, a facile synthetic approach for the preparation of blue emitting CsPbBr3 nanoplatelets (NPLs) with treatment by an organic sulfate is reported, 2,2‐(ethylenedioxy) bis(ethylammonium) sulfate (EDBESO4), which exhibit remarkably enhanced photoluminescence quantum efficiency (PLQE) and stability as compared to pristine CsPbBr3 NPLs coated with oleylamines. The PLQE is improved from ≈28% for pristine CsPbBr3 NPLs to 85% for EDBESO4 treated CsPbBr3 NPLs. Detailed structural characterizations reveal that EDBESO4 treatment leads to surface passivation of CsPbBr3 NPLs by both EDBE2+ and SO42– ions, which helps to prevent the coalescence of NPLs and suppress the degradation of NPLs. A simple proof‐of‐concept device with emission peaked at 462 nm exhibits an external quantum efficiency of 1.77% with a luminance of 691 cd m−2 and a half‐lifetime of 20 min, which represents one of the brightest pure blue PeLEDs based on NPLs reported to date.

Quantum dynamical semigroups and stability

A one parameter semigroup of maps is said to be stable if it eventually decays to zero. Generally different topologies for convergence to zero give rise to different notions of stability. For Quantum Dynamical Semigroups (QDS), conservativity and stability may be thought of as exact opposites of each other. We derive some conditions for stability of a QDS and examine the interplay between the necessary and sufficient conditions for conservativity and stability. Some perturbation results are also obtained.

Quantum Conductance in Memristive Devices: Fundamentals, Developments, and Applications.

Quantum effects in novel functional materials and new device concepts represent a potential breakthrough for the development of new information processing technologies based on quantum phenomena. Among the emerging technologies, memristive elements that exhibit resistive switching, which relies on the electrochemical formation/rupture of conductive nanofilaments, exhibit quantum conductance effects at room temperature. Despite the underlying resistive switching mechanism having been exploited for the realization of next-generation memories and neuromorphic computing architectures, the potentialities of quantum effects in memristive devices are still rather unexplored. Here, a comprehensive review on memristive quantum devices, where quantum conductance effects can be observed by coupling ionics with electronics, is presented. Fundamental electrochemical and physicochemical phenomena underlying device functionalities are introduced, together with fundamentals of electronic ballistic conduction transport in nanofilaments. Quantum conductance effects including quantum mode splitting, stability, and random telegraph noise are analyzed, reporting experimental techniques and challenges of nanoscale metrology for the characterization of memristive phenomena. Finally, potential applications and future perspectives are envisioned, discussing how memristive devices with controllable atomic-sized conductive filaments can represent not only suitable platforms for the investigation of quantum phenomena but also promising building blocks for the realization of integrated quantum systems working in air at room temperature.

Efficient purification method for CsPbX3 perovskite quantum dots

CsPbX3 perovskite quantum dots (QDs) have attracted increasing attention for the applications of lighting and display due to their excellent properties. Although the preparation of perovskite QDs has been widely developed, there is still not a universal and efficient method to purify perovskite QDs, which is due to the labile ionic characteristics of the perovskites. Here, a new purification method is proposed by using the addition of a new antisolvent-dimethicone oil (DMO). Compared to the two commonly used purification methods (direct centrifugation and centrifugation with ethyl acetate antisolvent), the sample purified by DMO addition shows the highest photoluminescence quantum yield (PLQY) and stability. Besides, the yield of the samples obtained from DMO addition is also the highest. This new purification method is also suitable for the products prepared by the room temperature method, where large amounts of QDs with high PLQY can be acquired. Furthermore, a simple differential centrifugation method is designed based on this anti-solvent. Size-selected perovskite QDs with narrow size distribution are obtained from this differential centrifugation method.

Quantum speed limit and stability of coherent states in quantum gravity

Utilizing the program of expectation values in coherent states and its recently developed algorithmic tools, this letter investigates the dynamical properties of cosmological coherent states for loop quantum gravity. To this end, the quantum speed limit (QSL) is adapted to quantum gravity, yielding necessary consistency checks for any proposal of stable families of states. To showcase the strength of the developed tools, they are applied to a prominent model: the Euclidean part of the quantum scalar constraint. We report the variance of this constraint evaluated on a family of coherent states showing that, for short times, this family passes the QSL test, allowing the transition from one coherent state to another one.

Quasienergy operators and generalized squeezed states for systems of trapped ions

Collective many-body dynamics for time-dependent quantum Hamiltonians is investigated for a dynamical system that exhibits multiple degrees of freedom, in this case a combined (Paul and Penning) trap. Quantum stability is characterized by a discrete quasienergy spectrum, while the quasienergy states are symplectic coherent states. We introduce the generators of the Lie algebra of the symplectic group SL(2,R), which we use to build the coherent states (CS) associated to the system under investigation. The trapped ion is treated as a harmonic oscillator (HO) to which we associate the quantum Hamilton function. We obtain the kinetic and potential energy operators as functions of the Lie algebra generators and supply the expressions for the classical coordinate, momentum, kinetic and potential energy, along with the total energy. Moreover, we also infer the dispersions for the coordinate and momentum, together with the asymmetry and the flatness parameter for the distribution. The system interaction with laser radiation is also examined for a system of identical two-level atoms. The Hamilton function for the Dicke model is derived. The optical system is modelled as a HO (trapped ion) that undergoes interaction with an external laser field and we use it to engineer a squeezed state of the electromagnetic (EM) field. We consider coherent and squeezed states associated to both ion dynamics and to the EM field. The approach used enables one to build CS in a compact and smart manner by use of the group theory.

Bulky and Stable Copper(I)-Phenanthroline Complex: Impact of Steric Strain and Symmetry on the Excited-State Properties.

The steric strain around copper(I) in typical [Cu(NNR)2]+ complexes, where NNR is a diimine ligand substituted in α-positions of the nitrogen atoms by R, is known to strongly impact the excited-state properties. Generally speaking, the larger the R, the longer the emission lifetime and the higher the quantum yield. However, the stability of the coordination scaffold can be at stake if the steric strain imposed by R is too large. In this work, we explore a way of fine-tuning the steric strain around Cu(I) to reach a balance between high emission quantum yield and stability in a highly bulky copper(I) complex. Taking stable [Cu(dipp)2]+ and unstable [Cu(dtbp)2]+ (where dipp and dtbp are, respectively, 2,9-diisopropyl-1,10-phenanthroline and 2,9-di-tert-butyl-1,10-phenanthroline) as the boundary of two least and most sterically strained structures, we designed and characterized the nonsymmetrical ligand 2-isopropyl-9-tert-butyl-1,10-phenanthroline (L1) and corresponding complex [Cu(L1)2]+ (Cu1). The key experimental findings are that Cu1 exhibits a rigid tetrahedral geometry in the ground state, close to that of [Cu(dtbp)2]+ and with an intermediate stability between that of [Cu(dipp)2]+ and [Cu(dtbp)2]+. Conversely, the nonsymmetrical nature of ligand L1 leads to a shorter emission lifetime and smaller quantum yield than those of either [Cu(dipp)2]+ or [Cu(dtbp)2]+. This peculiar behavior is rationalized through the in depth analysis of the ultrafast dynamics of the excited state measured with optical transient absorption spectroscopy and theoretical calculations performed on the ground and excited state of Cu1. Our main findings are that the obtained complex is significantly more stable than [Cu(dtbp)2]+ despite the sterically strained coordination sphere. The nonsymmetrical nature of the ligand translates into a strongly distorted structure in the excited state. The distortion can be described as a rocking motion of one ligand, entailing the premature extinction of the excited state via several deactivation channels.