Long-lived Charge Research Articles

Harnessing Intermolecular Interactions to Promote Long-Lived Photoinduced Charge Separation from Copper Phenanthroline Chromophores

Facilitating photoinduced electron transfer (PET) while minimizing rapid charge-recombination processes to produce a long-lived charge-separated (CS) state represents a primary challenge associated with achieving efficient solar fuel production. Natural photosynthetic systems employ intermolecular interactions to arrange the electron-transfer relay in reaction centers and promote a directional flow of electrons. This work explores a similar tactic through the synthesis and ground- and excited-state characterization of two Cu(I)bis(phenanthroline) chromophores with homoleptic and heteroleptic coordination geometries and which are functionalized with negatively charged sulfonate groups. The addition of sulfonate groups enables solubility in pure water, and it also induces assembly with the dicationic electron acceptor methyl viologen (MV2+) via bimolecular, dynamic electrostatic interactions. The effect of the sulfonate groups on the ground- and excited-state properties was evaluated by comparison with the unsulfonated analogues in 1:1 acetonitrile/water. The excited-state lifetimes for all sulfonated complexes are similar to what we expect from previous literature, with the exception of the sulfonated heteroleptic complex whose metal-to-ligand charge-transfer (MLCT) lifetime in water has two components that are fit to 10 and 77 ns. For the sulfonated complexes, we detected reduced MV+• in both solvent environments following MLCT excitation, but control measurements in 1:1 acetonitrile/water with the unsulfonated analogues showed no PET to MV2+, indicating that electrostatically driven supramolecular assemblies of the sulfonated complexes with MV2+ facilitate the observed PET. Additionally, the strength of the intermolecular interactions driving the formation of these assemblies changes drastically with the solvent environment. In 1:1 acetonitrile/water, PET occurred from both sulfonated complexes with quantum yields (ΦET) of 2-3% but increased to a remarkable 98% for the sulfonated heteroleptic complex with a 3 μs CS-state lifetime in water.

A Carbon Nanotube Binding BODIPY-C60 Nano Tweezer: Charge Stabilization through Sequential Electron Transfer.

Electron donor-acceptor (DA) hybrids comprised of single-wall carbon nanotubes (SWCNTs) are promising functional materials for light energy conversion. However, the DA hybrids built on SWCNTs have failed to reveal the much-sought long-lived charge separation (CS) due to the close proximity of the DA entities facilitating charge recombination. Here, we address this issue and report an elegant strategy to build multi-modular DA hybrids capable of producing long-lived CS states. For this, a nano tweezer featuring V-shape configured BODIPY was synthesized to host SWCNTs of different diameters via π-stacking. Supported by spectral, electrochemical, and computational studies, the established energy scheme revealed the possibility of sequential electron transfer. Systematic pump-probe studies covering wide spatial and temporal scales provided evidence of CS from the initial 1 BODIPY* ultimately resulting in C60 ⋅- -BODIPY-SWCNT⋅+ CS states of lifetimes in the 20-microsecond range.

Bimolecular reactivity of 3d metal-centered excited states (Cr, Mn, Fe, Co)

Metal-centered (MC) excited states (ESs) of 3d transition metal complexes (TMCs) often possess rather low energies so that these represent the lowest energy ESs. Additionally, MC states are often strongly distorted, hence they efficiently decay non-radiatively to the ground state. As bimolecular photoinduced electron transfer (PET) and energy transfer (EnT) processes require contact to the substrate, the metal confinement of the ES wavefunction of MC states makes these processes challenging. Consequently, MC states are considered less useful as compared to long-lived charge transfer states of higher energy with wavefunctions extending onto the ligands. Despite these supposed drawbacks, some classes of TMCs can successfully engage in bimolecular PET and EnT processes with MC states being the photoactive states. We discuss these initial examples of MC ES reactivity covering chromium, manganese, iron, and cobalt complexes with the aim to gain a deeper understanding of these processes and to identify the decisive key parameters. Finally, we present catalytic photoredox and energy transfer processes using photosensitizers with suitable MC ESs.

Polarization and depolarization control of single crystal CVD diamond detectors by UV and visible light illumination

Diamond detectors are known to suffer from the unwanted polarization phenomenon, when long-lived charge traps in the crystal bulk are charged during irradiation process and build up an electric field opposite to the bias field, deteriorating the detector performance. Here, we studied the polarization processes for diamond detectors made up of commercial high-quality single-crystal CVD diamonds in electric field of 1 V/μm with a focus on effect of light illumination on the polarization/depolarization dynamics, using a set of light emitting diodes operated from ultraviolet to red spectral range. The crystals irradiated with α-particles were characterized with the measurement of energy spectra and the transient current technique. The exposure to near-UV and blue light is found to induce a transient photocurrent (presumably via photoionization of nitrogen-related defects), which fills the charge traps, so the biased detector is polarized even if not irradiated, while longer wavelengths have a little effect. Without the biasing, the illumination speeds up the depolarization process, particularly, the exposure to 365 nm wavelength light can return the strongly polarized diamond detector into initial state in less than in 300 ms. The light illumination is concluded to be a convenient and speedy way to control/switch the polarization/depolarization processes of the diamond detectors.

Traps in the spotlight: How traps affect the charge carrier dynamics in Cs2AgBiBr6 perovskite

Suitable optoelectronic properties of lead halide perovskites make these materials interesting semiconductors for many applications. Toxic lead can be substituted by combining monovalent and trivalent cations, such as in Cs 2 AgBiBr 6 . However, efficiencies of Cs 2 AgBiBr 6 -based photovoltaics are still modest. To elucidate the loss mechanisms, in this report, we investigate charge dynamics in Cs 2 AgBiBr 6 films by double-pulse excitation time-resolved microwave conductivity (DPE-TRMC). By exciting the sample with two laser pulses with identical wavelengths, we found a clear photoconductance enhancement induced by the second pulse even 30 μs after the first laser pulse. Modeling the DPE-TRMC results, complemented by photoluminescence and transient absorption, we reveal the presence of deep emissive electron traps, while shallow hole trapping is responsible for the long-lived transient absorption signals. These long-lived carriers offer interesting possibilities for X-ray detectors or photocatalysis. The DPE-TRMC methodology offers unique insight into the times involved in charge trapping and depopulation in Cs 2 AgBiBr 6 . • Double-pulse excitation TRMC is developed to study trapping processes • Cs 2 AgBiBr 6 shows high photoconductance up to 30 μs after the first excitation • A high yield of free charges results from populated trap states by the first pulse • Emission of holes residing in shallow states extends over many microseconds Trap-assisted electron recombination in Cs 2 AgBiBr 6 thin films, combined with low hole mobility and shallow trapping, can be a major drawback of Cs 2 AgBiBr 6 in photovoltaic devices. Caselli et al. reveal that the long-lived charge carriers in Cs 2 AgBiBr 6 can offer a suitable, lead-free alternative for other applications, such as X-ray detectors or photocatalysis.

Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt Phthalocyanine: Long-Lived Charge Separation and Visible-Light-Driven Photocatalytic Activity

Unusual Electronic Properties of Cellulose Nanocrystals Conjugated to Cobalt Phthalocyanine: Long-Lived Charge Separation and Visible-Light-Driven Photocatalytic Activity

Enhanced photocatalytic H2 evolution based on a polymer/TiO2 film heterojunction

Polymer heterojunctions have emerged as promising photocatalysts for the photocatalytic hydrogen evolution. However, they are usually used in the form of suspended powder due to the low solubility and lack of anchoring groups to hybridize with inorganic semiconductor oxides. Yet polymer film heterojunctions with convenient separation and recycling potential are more suitable for large-scale water splitting. Herein, a new solution-processable polymer PDBCOOH with biphenyl as the electron donor and diketopyrrolopyrrole (DPP) containing carboxyl group as the electron acceptor has been designed and synthesized. Surface anchoring of PDBCOOH to TiO2 films through covalent bonding formed polymer-TiO2 film heterojunctions that achieved a recorded photocatalytic H2 production rate of 11.9 mmol/m2/h without Pt co-catalyst and was 88.8 times higher than that of pristine TiO2 film. Transient absorption spectroscopy confirms ultrafast polymer excited state electron injection into TiO2, long-lived charge separated state, and unity yield of polymer hole regeneration. Photoelectrochemical experiments combined with density functional theory calculation further demonstrate that polymer PDBCOOH/TiO2 film heterojunctions not only accelerate the charge transfer but also significantly improve the hydrogen evolution rate and stability of the photocatalysts. This work offers a new strategy for obtaining stable and efficient photocatalysts by using the covalent anchoring strategy of polymer/TiO2 film heterojunction.

Selenoviologen-Appendant Metallacycles with Highly Stable Radical Cations and Long-Lived Charge Separation States for Electrochromism and Photocatalysis.

Two coordinated metallacycles (rhomboid for M1, hexagonal for M2) with selenoviologens (SeV2+ ) pendants were synthesized via coordination-driven hierarchical self-assembly. M1/M2 with rigid and discrete metallacyclic cores showed tunable optoelectronic properties due to strong π-π stacking and push-pull electron structures. Femtosecond transient absorption (fs-TA) revealed that the formation of macrocyclic structure can not only enhance the stability of radical cation, but also improve the efficiency of intramolecular charge transfer and produce a long-lived charge separation state. The electrochromic performances of M1/M2-based devices were exhibited to show decent radical stabilization. By using M1/M2 as the photocatalyst, the improved catalytic efficiency (>80 %) of visible-light-induced cross-dehydrogenative coupling (CDC) reactions was achieved due to the highly stable radical cations and long-lived charge separation states, which were also confirmed by fs-TA.

Mn‐Doped Perovskite Nanocrystals for Photocatalytic CO2 Reduction: Insight into the Role of the Charge Carriers with Prolonged Lifetime

Halide Perovskite Photocatalysts In article number 2200294, Jin Wang, Zhengquan Li, and co-workers developed a halide perovskite photocatalyst with long-lived charge carriers by doping Mn as an electron storage. This work provides an effective strategy to regulate charge transfer pathways and achieve high-efficient halide perovskite photocatalytic systems.

Molecular Triplet Sensitization of Monolayer Semiconductors in 2D Organic/Inorganic Hybrid Heterostructures.

Hybrid heterostructures (HSs) comprising organic and two-dimensional (2D) monolayer semiconductors hold great promise for optoelectronic applications. So far, research efforts on organic/2D HSs have exclusively focused on coupling directly photoexcited singlets to monolayer semiconductors. It remains unexplored whether and how the optically dark triplets in organic semiconductors with intriguing properties (e.g., long lifetime) can be implemented for modulating light-matter interactions of hybrid HSs. Herein, we investigate the triplet sensitization of monolayer semiconductors by time-resolved spectroscopic studies on Pd-octaethylporphyrin (PdOEP)/WSe2 and PdOEP/WS2 HSs with type I and type II band alignment, respectively. We show that PdOEP triplets formed in ∼5 ps from intersystem crossing can transfer energy or charge to WSe2 or WS2 monolayers, respectively, leading to a significant photoluminescence enhancement (180%) in WSe2 or long-lived charge separation (>2 ns) in WS2. The triplet transfer occurs in ∼100 ns, which is more than 3 orders of magnitude slower than singlet and can be attributed to its tightly localized nature. Further study of thickness dependence reveals the dictating role of triplet diffusion for triplet sensitization in organic/2D HSs. This study shows the great promise of much less explored molecular triplets on sensitizing 2D monolayer semiconductors and provides the guidance to achieve long-range light harvesting and energy migration in organic/2D HSs for enhanced optoelectronic applications.

Photoinduced Charge Transfer from Quantum Dots Measured by Cyclic Voltammetry.

Measuring and modulating charge-transfer processes at quantum dot interfaces are crucial steps in developing quantum dots as photocatalysts. In this work, cyclic voltammetry under illumination is demonstrated to measure the rate of photoinduced charge transfer from CdS quantum dots by directly probing the changing oxidation states of a library of molecular charge acceptors, including both hole and electron acceptors. The voltammetry data demonstrate the presence of long-lived charge donor states generated by native photodoping of the quantum dots as well as a positive correlation between driving force and rate of charge transfer. Changes to the voltammograms under illumination follow mechanistic predictions from the ErCi' zone diagram, and electrochemical modeling allows for measurement of the rate of productive electron transfer. Observed rates for photoinduced charge transfer are on the order of 0.1 s-1, which are distinct from the picosecond dynamics measured by conventional transient optical spectroscopy methods and are more closely connected to the quantum yield of light-mediated chemical transformations.

Observing the On-Site Generation of Excitons and Charges by Low-Temperature Spectroscopy.

Understanding the relation between phase morphology and physical processes in polymer blends is the key to the fabrication of reproducible and reliable polymer optoelectronic devices. In this work, taking the advantage of low-temperature spectroscopy, we have observed the on-site generation of excitons and long-lived charges in different phase morphology polymer/fullerene blends. Probing at 10K, the photo-generated species are localized to where they are generated. We found that the generation of excitons and long-lived charges is highly influenced by the local molecular phase morphology. We further demonstrated that although the influence of phase morphology is localized to the place that excitons and long-lived charges are generated, this influence can persist over sub-millisecond timescales. Thus, we believe that the fate of excitons and long-lived charges is determined by the location at which they are generated, which can in turn be controlled precisely by molecular phase morphology.

(Invited, Digital Presentation) Donor-Acceptor-Linked Molecules for Controlling the Membrane Potential of Living Cells

Living animal cells have the plasma membrane potential (V m), which results from a difference in the electrical charge on the two extreme sides of the plasma membrane, that is, a slight excess of positive and negative ions outside and inside a cell, respectively. Such a difference is controlled by various ion channels. In neuronal cells, the V m is negative in the resting state and is drastically changed for neurotransmission. In response to some input, the ion channels of neuronal cells get quickly and transiently activated such that the abovementioned difference is cancelled (∆V m > 0, depolarization). Coordinated activation and deactivation of the ion channels occurs along the neuronal axons, which generates electrical pulses. This is the mechanism of neurotransmission. Therefore, the control of the V m using a light source is an attractive strategy that can allow targeted, fast control of neuronal activities. In this symposium, we have demonstrated a novel general strategy for the control of the V m by using donor-acceptor-linked molecules (D-A molecules) capable of intramolecular long-lived charge separation, nanocarriers for membrane targeting of D-A molecules, and light.The D-A molecules used in this study were triadic complexes of ferrocene (Fc), porphyrin (H2P), and fullerene (C60) (Fc-H2P-C60). We had previously reported that, under light irradiation, Fc-H2P-C60 yields the ferrocenium cation (Fc+)-H2P-C60 radical anion (C60 •-) with a long lifetime of ~0.01 ms [1]. Fc-H2P-C60 was solubilized in the physiological media with a genetically engineered lipoprotein nanoparticle (cpHDL). cpHDL was capable of high plasma membrane binding without significant cytotoxicity [2]. The Fc-H2P-C60/cpHDL complex was added to a cell culture medium of neuronal cells (rat pheochromocytoma PC12), and its plasma membrane binding was confirmed by confocal analysis and freeze-fracture electron microscopy. Subsequent light irradiation of PC12 cells decreased the membrane potential (∆V m > 0, depolarization). Such depolarization was not observed for the reference molecule (H2P alone) that was incapable of charge separation, clearly demonstrating that the charge separation was responsible for this depolarization [3]. Our following study with other D-A molecules revealed that the degree of the depolarization was positively correlated with the charge separation yield [4].To gain insight into the mechanism of this photo-induced depolarization, cytotoxicity, channel activities, and membrane capacitance were evaluated in D-A molecule-treated PC12 cells under or after irradiation. Pore formation in the plasma membrane, resulting from severe membrane damage, were not detected. Indeed, the photo-generation of reactive oxygen species (ROS) leading to membrane disruption was less efficient in the D-A molecules than in H2P incapable of photo-induced charge separation. In contrast, it was found that a specific subtype of cation channels was inhibited, and that the membrane capacitance was decreased by irradiated D-A molecules [5]. In this symposium, I will discuss more about the potential of applying our D-A molecules/carriers system in the biomedical fields.REFERENCES[1] Imahori, H. et al., J. Am. Chem. Soc. 2001, 123, 2607-2617.[2] Nakatsuji, H. et al., Angew. Chem. Int. Ed. 2015, 54, 11725-11729.[3] Numata, T. et al., J. Am. Chem. Soc. 2012, 134, 6092-6095.[4] Takano, Y. et al., Chem. Sci. 2016, 7, 3331-3337.[5] Numata, T. et al., Cell. Physiol. Biochem. 2020, 54, 899-916.

Long-range transport and ultrafast interfacial charge transfer in perovskite/monolayer semiconductor heterostructure for enhanced light absorption and photocarrier lifetime.

Atomically thin two-dimensional transition metal dichalcogenides (TMDs) have shown great potential for optoelectronic applications, including photodetectors, phototransistors, and spintronic devices. However, the applications of TMD-based optoelectronic devices are severely restricted by their weak light absorption and short exciton lifetime due to their atomically thin nature and strong excitonic effect. To simultaneously enhance the light absorption and photocarrier lifetime of monolayer semiconductors, here, we report 3D/2D perovskite/TMD type II heterostructures by coupling solution processed highly smooth and ligand free CsPbBr3 film with MoS2 and WS2 monolayers. By time-resolved spectroscopy, we show interfacial hole transfer from MoS2 (WS2) to the perovskite layer occurs in an ultrafast time scale (100 and 350fs) and interfacial electron transfer from ultrathin CsPbBr3 to MoS2 (WS2) in ∼3 (9) ps, forming a long-lived charge separation with a lifetime of >20ns. With increasing CsPbBr3 thickness, the electron transfer rate from CsPbBr3 to TMD is slower, but the efficiency remains to be near-unity due to coupled long-range diffusion and ultrafast interfacial electron transfer. This study indicates that coupling solution processed lead halide perovskites with strong light absorption and long carrier diffusion length to monolayer semiconductors to form a type II heterostructure is a promising strategy to simultaneously enhance the light harvesting capability and photocarrier lifetime of monolayer semiconductors.

Donor-acceptor organic semiconductor heterojunction nanoparticles for efficient photocatalytic H2 evolution

Donor-acceptor organic semiconductor heterojunction nanoparticles are currently among the most efficient visible-light-active H2 evolution photocatalysts due to their long-lived reactive charges. In the current issue of Nature Energy, McCulloch et al. developed two donor-acceptor organic semiconductors with heterojunction nanoparticles for highly efficient photocatalytic H2 evolution. Donor-acceptor organic semiconductor heterojunction nanoparticles are currently among the most efficient visible-light-active H2 evolution photocatalysts due to their long-lived reactive charges. In the current issue of Nature Energy, McCulloch et al. developed two donor-acceptor organic semiconductors with heterojunction nanoparticles for highly efficient photocatalytic H2 evolution.

Enhancing photocurrent of dye-sensitized solar cells through solvent modulating aggregation of dyes

Aggregation of organic molecules plays a key role in determining the photoelectronic properties of various devices. However, the formation of aggregates is an outcome of complex synergistic effects of various intermolecular forces, and changes with the molecular structure and environment. Here we exploit the aggregation of two dyes with (MTPABT-Pyc) or without (MTPAcc) the nanosecond long-lived charge separation state and their effect on photovoltaic performance of dye-sensitized solar cells (DSSCs). Different solvent systems were selected to modulate the interactions between solvents and dye molecules for the effects on photophysical processes. Combining the experimental results on the solvent effect on dye aggregation with theoretical calculations reveals that MTPAcc inclines to form H-aggregation on the TiO2 surface because of the decisive role of its molecular structure. The solvent regulation has a great impact on MTPABT-Pyc which can make aggregates transform between H-aggregation and J-aggregation. The effects of aggregation on the device performance of two dyes are completely opposite. High performance of MTPAcc depends on the co-adsorbent chenodeoxycholic acid, which could suppress the dye aggregation. In contrast, the aggregation of MTPABT-Pyc will not harm the charge separation and transportation processes in devices and shows a positive effect on the cell performance due to the aggregation exhibiting broader absorption bands. As the photocurrent contribution by the aggregation-induced long-wavelength absorption increases from 9% (H-aggregation) to 34% (J-aggregation), the short-circuit current (Jsc) and the power conversion efficiency (PCE) of MTPABT-Pyc increased by 13% and 14%, respectively. These results pave a new way for taking full advantage of the aggregation of molecules to realize high-performance light-to-current conversion.

Controlling Symmetry Breaking Charge Transfer in BODIPY Pairs.

Symmetry breaking charge transfer (SBCT) is a process in which a pair of identical chromophores absorb a photon and use its energy to transfer an electron from one chromophore to the other, breaking the symmetry of the chromophore pair. This excited state phenomenon is observed in photosynthetic organisms where it enables efficient formation of separated charges that ultimately catalyze biosynthesis. SBCT has also been proposed as a means for developing photovoltaics and photocatalytic systems that operate with minimal energy loss. It is known that SBCT in both biological and artificial systems is in part made possible by the local environment in which it occurs, which can move to stabilize the asymmetric SBCT state. However, how environmental degrees of freedom act in concert with steric and structural constraints placed on a chromophore pair to dictate its ability to generate long-lived charge pairs via SBCT remain open topics of investigation.In this Account, we compare a broad series of dipyrrin dimers that are linked by distinct bridging groups to discern how the spatial separation and mutual orientation of linked chromophores and the structural flexibility of their linker each impact SBCT efficiency. Across this material set, we observe a general trend that SBCT is accelerated as the spatial separation between dimer chromophores decreases, consistent with the expectation that the electronic coupling between these units varies exponentially with their separation. However, one key observation is that the rate of charge recombination following SBCT was found to slow with decreasing interchromophore separation, rather than speed up. This stems from an enhancement of the dimer's structural rigidity due to increasing steric repulsion as the length of their linker shrinks. This rigidity further inhibits charge recombination in systems where symmetry has already enforced zero HOMO-LUMO overlap. Additionally, for the forward transfer, the active torsion is shown to increase LUMO-LUMO coupling, allowing for faster SBCT within bridging groups.By understanding trends for how rates of SBCT and charge recombination depend on a dimer's internal structure and its environment, we identify design guidelines for creating artificial systems for driving sustained light-induced charge separation. Such systems can find application in solar energy technologies and photocatalytic applications and can serve as a model for light-induced charge separation in biological systems.

Highly efficient photocatalytic hydrogen production via porphyrin-fullerene supramolecular photocatalyst with donor-acceptor structure

A novel tetraphenylporphyrin-C60 supramolecular photocatalyst (SA-TPP-C60) with donor–acceptor (D-A) structure is successfully constructed. Self-assembly of covalently-linked D-A molecule TPP-C60 gives rise to SA-TPP-C60 with highly-ordered layered D-A structure. TPP-C60 molecule is characterized with strong D-A interaction, inducing a significantly larger molecular dipole moment (ca. 4.86 D) than the referential TPP molecule (only 0.04 D). In consequence, robust internal electric field (IEF) with 4.7 times enhancement is built up in SA-TPP-C60, contributing to ultrafast photogenerated charge separation (∼0.5 ps) and enhanced charge transport. Notably, unprecedented long-lived photogenerated charge separation (τ = 26.3 ns) was observed in SA-TPP-C60. Thus, the photocatalytic hydrogen evolution performance of SA-TPP-C60 reached 10.69 mmol g-1h−1, which is about 80 times higher than SA-TPP. Briefly, this study sheds light on D-A structure engineering of supramolecular photocatalysts for high-performance photocatalytic applications.

Long-Lived Charge-Transfer State in Spiro Compact Electron Donor-Acceptor Dyads Based on Pyromellitimide-Derived Rhodamine: Charge Transfer Dynamics and Electron Spin Polarization.

We observed a long‐lived charge transfer (CT) state in a novel orthogonal compact electron donor–acceptor dyads, with closed form of rhodamine (Rho) as electron donor and pyromellitimide (PI),or thionated PI, as electron acceptor. The two parts in the dyads are connected via a spiro quaternary carbon atom, thus the torsion between the donor and acceptor is completely inhibited, which is beneficial to reduce the reorganization energy and to exploit the Marcus inverted region effect to prolong the CT state lifetime. Femtosecond transient absorption spectra show that the charge separation is rather fast, while nanosecond transient absorption spectra confirmed the formation of long‐lived CT state (2.6 μs). Time‐resolved electron paramagnetic resonance (TREPR) spectra determined the spin multiplicity of the long living state and assigned it to a 3CT state. Replacement of an oxygen atom in the PI part with a sulfur atom favoring classical intersystem crossing processes, causes a consistently shortening of the lifetime of the 3CT state (0.29 μs).

Photoinduced Transformation of Cs2Au2Br6 into CsPbBr3 Nanocrystals.

Lead-free halide double perovskites offer an environmentally friendly alternative to lead halide perovskites for designing optoelectronic solar cell devices. One simple approach to synthesize such double halide perovskites is through metal ion exchange. CsPbBr3 nanocrystals undergo exchange of Pb2+ with Au(I)/Au(III) to form double perovskite Cs2Au2Br6. When excited, a majority of the charge carriers undergo quick recombination in contrast to long-lived charge carries of excited CsPbBr3 nanocrystals. This metal ion exchange process is reversible as one can regenerate CsPbBr3 by adding excess PbBr2 to the suspension. Interestingly, when subjected to visible light irradiation, Cs2Au2Br6 nanocrystals eject reduced Au from the lattice as evidenced from the formation of larger gold nanoparticles. The presence of residual Pb2+ ions in the suspension restores the original CsPbBr3 composition. The results presented here provide insight into the dynamic nature of Au within the perovskite lattice under both chemical and light stimuli.