Singlet Energy Transfer Research Articles

Triad photosensitizers based on iodo-aza-Bodipy and naphthalenediimides (NDI) with broadband absorption: Study of resonance energy transfer and electron transfer

Two organic photosensitizers based on resonance energy transfer (A-1 and A-2) are prepared. Naphthalenediimides was used as intramolecular energy donor and iodo-aza-Bodipy was used as intramolecular energy acceptor/spin converter. A-1 (ε = 42,800 at 618 nm and ε = 59,600 at 674 nm) and A-2 (ε = 33,300 at 514 nm and ε = 68,300 at 674 nm) give the two strong absorption band and both of them show broadband absorption in visible region. The photophysical properties of the compounds were studied with steady state and time-resolved spectroscopy in detail. With steady state and time-resolved spectroscopy, we found that photoexcitation into the energy donor was followed by singlet energy transfer, then via the intersystem crossing (ISC) of the energy acceptor. By nanosecond time-resolved transient absorption spectroscopy and DFT calculation, triplet excited state is localized on the iodo-aza-Bodipy moiety. Quantum yield of singlet oxygen of A-1 and A-2 is 39.7 % and 40.9 %, respectively. Based on fluorescence lifetime quenching, the efficiency of intramolecular energy transfer is estimated to be 15.9 % and 27.7 % for A-1 and A-2. And PET is responsible for the relatively low efficiency, which is identified by the calculation of kcs/kFRET and the Gibbs free energy change (△G0cs). A-1 and A-2 were used for singlet oxygen (1O2) mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability are more efficient than the triplet photosensitizers with the mono-chromophore photosensitizer.

Distance-Independent Efficiency of Triplet Energy Transfer from π-Conjugated Organic Ligands to Lanthanide-Doped Nanoparticles.

Lanthanide-doped nanoparticles (LnNPs) possess unique optical properties and are employed in various optoelectronic and bioimaging applications. One fundamental limitation of LnNPs is their low absorption cross-section. This hurdle can be overcome through surface modification with organic chromophores with large absorption cross-sections. Controlling energy transfer from organic molecules to LnNPs is crucial for creating optically bright systems, yet the mechanisms are not well understood. Using pump-probe spectroscopy, we follow singlet energy transfer (SET) and triplet energy transfer (TET) in systems comprising different length 9,10-bis(phenylethynyl)anthracene (BPEA) derivatives coordinated onto ytterbium and neodymium-doped nanoparticles. Photoexcitation of the ligands forms singlet excitons, some of which convert to triplet excitons via intersystem crossing when coordinated to the LnNPs. The triplet generation rate and yield are strongly distance-dependent. Following their generation, TET occurs from the ligands to the LnNPs, exhibiting an exponential distance dependence, independent of solvent polarity, suggesting a concerted Dexter-type process with a damping coefficient of 0.60 Å-1. Nevertheless, TET occurs with near-unity efficiency for all BPEA derivatives due to the lack of other triplet deactivation pathways and long intrinsic triplet lifetimes. Thus, we find that close coupling is primarily important to ensure efficient triplet generation rather than efficient TET. Although SET is faster, we find its efficiency to be lower and more strongly distance-dependent than the TET efficiency. Our results present the first direct distance-dependent energy transfer measurements in LnNP@organic nanohybrids and establish the advantage of using the triplet manifold to achieve the most efficient energy transfer and best sensitization of LnNPs with π-conjugated ligands.

Electronic Couplings for Triplet-Triplet Annihilation Upconversion in Crystal Rubrene.

Triplet-triplet annihilation photon upconversion (TTA-UC) is a process able to repackage two low-frequency photons into light of higher energy. This transformation is typically orchestrated by the electronic degrees of freedom within organic compounds possessing suitable singlet and triplet energies and electronic couplings. In this work, we propose a computational protocol for the assessment of electronic couplings crucial to TTA-UC in molecular materials and apply it to the study of crystal rubrene. Our methodology integrates sophisticated yet computationally affordable approaches to quantify couplings in singlet and triplet energy transfer, the binding of triplet pairs, and the fusion to the singlet exciton. Of particular significance is the role played by charge-transfer states along the b-axis of rubrene crystal, acting as both partial quenchers of singlet energy transfer and mediators of triplet fusion. Our calculations identify the π-stacking direction as holding notable triplet energy transfer couplings, consistent with the experimentally observed anisotropic exciton diffusion. Finally, we have characterized the impact of thermally induced structural distortions, revealing their key role in the viability of triplet fusion and singlet fission. We posit that our approaches are transferable to a broad spectrum of organic molecular materials, offering a feasible means to quantify electronic couplings.

Ultrafast energy transfer dynamics in CsPbBr3 nanoplatelets-BODIPY heterostructure.

Understanding and directing the energy transfer in nanocrystals-chromophore heterostructure is critical to improve the efficiency of their photocatalytic and optoelectronic applications. In this work, we studied the energy transfer process between inorganic-organic molecular complexes composed of cesium halide perovskite nanoplatelets (CsPbBr3 NPLs) and boron dipyrromethene (BODIPY) by photoluminescence spectroscopy (PL), time-correlated single photon-counting (TCSPC) and femtosecond transient absorption spectroscopy. The quenching of PL in CsPbBr3 NPLs occurred simultaneously with the PL enhancement of BODIPY implied the singlet energy transfer process. The rate of energy transfer has been determined by transient absorption spectrum as kET = 3.8 × 109 s-1. The efficiency of Förster energy transfer (FRET) has been quantitatively calculated up to 70%. Our work advances the understanding of the interaction between BODIPY and perovskite nanoplatelets, providing a new solution based on their optoelectronic and photocatalytic applications.

Tuning Energy Transfer Pathways in Halide Perovskite-Dye Hybrids through Bandgap Engineering.

Lead halide perovskite nanocrystals, which offer rich photochemistry, have the potential to capture photons over a wide range of the visible and infrared spectrum for photocatalytic, optoelectronic, and photon conversion applications. Energy transfer from the perovskite nanocrystal to an acceptor dye in the form of a triplet or singlet state offers additional opportunities to tune the properties of the semiconductor-dye hybrid and extend excited-state lifetimes. We have now successfully established the key factors that dictate triplet energy transfer between excited CsPbI3 and surface-bound rhodamine dyes using absorption and emission spectroscopies. The pendant groups on the acceptor dyes influence surface binding to the nanocrystals, which in turn dictate the energy transfer kinetics, as well as the efficiency of energy transfer. Of the three rhodamine dyes investigated (rhodamine B, rhodamine B isothiocyanate, and rose Bengal), the CsPbI3-rose Bengal hybrid with the strongest binding showed the highest triplet energy transfer efficiency (96%) with a rate constant of 1 × 109 s-1. This triplet energy transfer rate constant is nearly 2 orders of magnitude slower than the singlet energy transfer observed for the pure-bromide CsPbBr3-rose Bengal hybrid (1.1 × 1011 s-1). Intriguingly, although the single-halide CsPbBr3 and CsPbI3 nanocrystals selectively populate singlet and triplet excited states of rose Bengal, respectively, the mixed halide perovskites were able to generate a mixture of both singlet and triplet excited states. By tuning the bromide/iodide ratio and thus bandgap energy in CsPb(Br1-xIx)3 compositions, the percentage of singlets vs triplets delivered to the acceptor dye was systematically tuned from 0 to 100%. The excited-state properties of halide perovskite-molecular hybrids discussed here provide new ways to modulate singlet and triplet energy transfer in semiconductor-molecular dye hybrids through acceptor functionalization and donor bandgap engineering.

Phase Control and Singlet Energy Transfer Enabled by Trimethylamine Modified Boron Dipyrromethene for Stable CsPbBr3 Quantum Wells

AbstractThe phase distribution and organic spacer cations play pivotal roles in determining the emission performance and stability of perovskite quantum wells (QWs). Here, we propose a universal molecular regulation strategy to tailor phase distribution and enhance the stability of CsPbBr3 QWs. The capability of sterically hindered ligands with formidable surface binding groups is underscored in directing CsPbBr3 growth and refining phase distribution. With trimethylamine modified boron dipyrromethene (BDP‐TMA) ligand as a representative, the BDP‐TMA driven can precisely control phase distribution and passivate defects of CsPbBr3. Notably, BDP‐TMA acts as a co‐spacer organic entity in obtained BDP‐TMA‐CsPbBr3, facilitating efficient singlet energy transfer and tailoring the luminescence to produce a distinctive bluish‐white emission. The BDP‐TMA‐CsPbBr3 demonstrates significant phase stability under water exposure, light irradiation, and moderate temperature. Interestingly, BDP‐TMA‐CsPbBr3 exhibits the thermally‐induced dynamic fluorescence control at elevated temperatures, which can be achieved feasible for advanced information encryption. This discovery paves the way for the exploration of perovskite QWs in applications like temperature sensing, anti‐counterfeiting, and other advanced optical smart technologies.

Phase Control and Singlet Energy Transfer Enabled by Trimethylamine Modified Boron Dipyrromethene for Stable CsPbBr3 Quantum Wells.

The phase distribution and organic spacer cations play pivotal roles in determining the emission performance and stability of perovskite quantum wells (QWs). Here, we propose a universal molecular regulation strategy to tailor phase distribution and enhance the stability of CsPbBr3 QWs. The capability of sterically hindered ligands with formidable surface binding groups is underscored in directing CsPbBr3 growth and refining phase distribution. With trimethylamine modified boron dipyrromethene (BDP-TMA) ligand as a representative, the BDP-TMA driven can precisely control phase distribution and passivate defects of CsPbBr3 . Notably, BDP-TMA acts as a co-spacer organic entity in obtained BDP-TMA-CsPbBr3 , facilitating efficient singlet energy transfer and tailoring the luminescence to produce a distinctive bluish-white emission. The BDP-TMA-CsPbBr3 demonstrates significant phase stability under water exposure, light irradiation, and moderate temperature. Interestingly, BDP-TMA-CsPbBr3 exhibits the thermally-induced dynamic fluorescence control at elevated temperatures, which can be achieved feasible for advanced information encryption. This discovery paves the way for the exploration of perovskite QWs in applications like temperature sensing, anti-counterfeiting, and other advanced optical smart technologies.

Extending Infrared Emission via Energy Transfer in a CsPbI3-Cyanine Dye Hybrid.

Directing energy flow in light harvesting assemblies of nanocrystal-chromophore hybrid systems requires a better understanding of factors that dictate excited-state processes. In this study, we explore excited-state interactions within the CsPbI3-cyanine dye (IR125) hybrid assembly through a comprehensive set of steady-state and time-resolved absorption and photoluminescence (PL) experiments. Our photoluminescence investigations reveal the quenching of CsPbI3 emission alongside the simultaneous enhancement of IR125 fluorescence, providing evidence for a singlet energy transfer. The evaluation of both photoluminescence (PL) quenching and PL decay measurements yield ∼94% energy transfer efficiency for the CsPbI3-IR125 hybrid assembly. Transient absorption spectroscopy further unveils that this singlet energy transfer process operates on an ultrafast time scale, occurring within 400 ps with a rate constant of energy transfer of 1.4 × 1010 s-1. Our findings highlight the potential of the CsPbI3-IR125 hybrid assembly to extend the emission of halide perovskites into the infrared region, paving the way for light energy harvesting and display applications.

Synthesis and properties of covalently linked phenyl bridged 3-pyrrolyl BODIPY–BODIPY dyads

Two different covalently linked 3-pyrrolyl BODIPY–BODIPY dyads were synthesized and their fluorescence studies indicated a possibility of singlet–singlet energy transfer from BODIPY to 3-pyrrolyl BODIPY unit.

Photoisomerization of Alkenes via Energy Transfer Enabled by Cu‐Acetylide Complexes

AbstractThis work demonstrates the isomerization of alkenes enabled by copper‐acetylide complexes under blue light. This system is applicable to the E→Z isomerization of α‐ and β‐substituted cinnamate derivatives with moderate to excellent Z/E ratios. A reaction pathway involving singlet energy transfer (EnT) from the copper‐acetylide complex to the alkene is proposed.

Spectro-luminescent characterization of molecular complex based on tryptanthrin for design of new effective drugs

Optical absorption (at room temperature), fluorescence (at room temperature and T = 78 K) and phosphorescence (at T = 78 K) spectra of solution of the molecular complex based on tryptanthrin with platinum chloride and DMSO [Pt(Try)(DMSO)Cl2] (Try-Pt) was investigated. The positions of the first excited singlet (S1) and triplet (T1) energy levels were obtained. It was shown that in the excited state intramolecular singlet excitations energy transfer inside tryptanthrin π-electron system between two centers of optical absorption (that absorb equally) exists. It was found out the optical response of toxic influence of platinum chloride on tryptanthrin π-electron system inside this molecular complex as it is shown by us for a number of polynucleotides. Contrary to singlet energy transfer no intramolecular triplet electronic excitations energy transfer inside tryptanthrin π-electron system between both optical centers is observed. Taking into account the facts that such complexes can easy bind to telomeric G4 DNA the studied phenomena can be used for the design of new effective antitumor and anti-inflammatory drugs.

Ratiometric probe of PQDs/R6G: Achieving high sensitivity and precision in contaminant detection

This paper discusses the utilization of water stable, biocompatible CsPbBr3 perovskite quantum dots (BPQDs) as donors in combination with Rhodamine 6G (R6G) as acceptors, as ratiometric probe, for detection of pathogens and water contaminants via the fluorescence resonance energy transfer (FRET) mechanism. Biocompatibility of BPQDs was attained through phase engineering using succinic acid (SA) ligand which at appropriate pH provides carboxylic environment on the outer surface, facilitating transfer to aqueous phase. Photoluminescence (PL) studies on ratiometric probe reveal quenching of BPQDs’ emission with a simultaneous enhancement of R6G fluorescence, representing a singlet energy transfer. The probe was successfully validated for ratiometric sensing of a model carcinogen (thioacetamide (TAA)) and a model pathogen (Escherichia coli (E. coli)) and the detection limit achieved was 1.8 CFU/mL for E. coli sensing and 1.5 µM for TAA sensing. Dual emission and its quenching mechanism involved in the detection of aforesaid analytes have been elaborately discussed and elucidated, indicating that quenching mechanisms are different for the two analytes. Our work not only demonstrates an important milestone for the integration of perovskite quantum dot in clinical diagnostics but also as an easy, unique, rapid and accurate E. coli detection technique that is complimentary to the rather complicated high throughput and high-sensitivity approaches that are existing.

TADF-Based X-ray Screens with Simultaneously Efficient Singlet and Triplet Energy Transfer for High Spatial Imaging Resolution.

X-ray imaging scintillators play a crucial role in medical examinations and safety inspections, making them an essential technology in our modern lives. However, commercially available high-performance scintillators are fabricated exclusively from ceramic materials that require harsh preparation conditions and are costly to produce. Organic scintillators have emerged as a promising alternative due to their transparency and ease of fabrication at a low cost. Unfortunately, organic scintillators suffer from inefficient exciton utilization efficiency, leading to poor performance in X-ray imaging screens and hindering their commercialization. In this study, we explore the use of thermally activated delayed fluorescence (TADF) chromophores (4CzIPN-I and 4CzTPN) to enhance the absorption of ionizing radiation in X-ray imaging screens by an order of magnitude. By leveraging the unique features of TADF chromophores through simultaneously singlet-singlet and triplet-triplet efficient energy transfers at the interface between two different TADF systems, we demonstrate an impressive X-ray sensitivity and radioluminescence intensity. Our time-resolved experiments and density functional theory (DFT) calculations provide further evidence for the effectiveness of this approach. The resulting X-ray imaging screens based on this efficient interfacial energy transfer process in TADF systems exhibit outstanding X-ray imaging resolution of 20 line pairs/mm, the highest resolution reported thus far for organic scintillators. This resolution is at least two times higher than that achieved by commonly used commercial inorganic scintillators in the X-ray imaging market. These findings introduce a new component for greatly improving the performance of organic X-ray imaging scintillators, supporting a wide range of emerging X-ray applications with exceptional spatial resolution.

Bodipy−corrole tetrads as heavy−atom−free triplet photosensitizers: Study of the energy transfer and application in triplet−triplet annihilation upconversion

Free base corrole can generate triplet state without invoking of heavy−atom effect, however, its weak and narrow absorption band in the visible spectral range make corrole not an ideal triplet photosensitizer. Herein, novel Bodipy−corrole tetrads were prepared by attaching visible light-harvesting antennae of Bodipy or electron spin converter with fullerene units (2B−Tur−Cor and B−C60−Tur−Cor) to solve the above problems, which show a stronger and broader absorption band in the visible region, and the maximum molar absorption coefficient is up to 2.58 × 105 M−1 cm−1 at 504 nm for 2B−Tur−Cor. By using of fluorescence spectroscopy, steady-state and time-resolved transient absorption spectroscopic methods, the singlet energy transfer progress from the Bodipy moiety to the corrole moiety was confirmed. Through fluorescence lifetimes and fluorescence excitation spectrum study, the rate constant of the singlet energy transfer was calculated as 9.58 × 107 s−1 for 2B−Tur−Cor and 2.45 × 108 s−1 for B−C60−Tur−Cor, respectively. The TD−DFT computation suggests that the first and second triplet state is localized in the corrole moiety and the Bodipy moiety for 2B−Tur−Cor, respectively, and the triplet state energy was calculated to be 1.37 eV and 1.61 eV, respectively. Nanosecond time−resolved transient difference absorption spectra show that the triplet excited states of these tetrads are localized on corrole unit, the lifetime of 2B−T−Cor is up to 143 μs, however, the lifetime of B−C60−Tur−Cor is only 3.3 μs. Long-lived triplet excited states play important role in applications of the triplet photosensitizers in photocatalysis or other photophysical processes concerning triplet–triplet−energy−transfer. As a proof of concept, these tetrads were used as heavy−atom−free organic triplet photosensitizers for triplet−triplet annihilation based upconversion. The upconversion quantum yield was up to 5.86% for 2B−Tur−Cor, however, it is only 0.52% for B−C60−Tur−Cor.

How Pendant Groups Dictate Energy and Electron Transfer in Perovskite–Rhodamine Light Harvesting Assemblies

Energy and electron transfer processes allow for efficient manipulation of excited states within light harvesting assemblies for photocatalytic and optoelectronic applications. We have now successfully probed the influence of acceptor pendant group functionalization on the energy and electron transfer between CsPbBr3 perovskite nanocrystals and three rhodamine-based acceptor molecules. The three acceptors─rhodamine B (RhB), rhodamine isothiocyanate (RhB-NCS), and rose Bengal (RoseB)─contain an increasing degree of pendant group functionalization that affects their native excited state properties. When interacting with CsPbBr3 as an energy donor, photoluminescence excitation spectroscopy reveals that singlet energy transfer occurs with all three acceptors. However, the acceptor functionalization directly influences several key parameters that dictate the excited state interactions. For example, RoseB binds to the nanocrystal surface with an apparent association constant (Kapp = 9.4 × 106 M-1) 200 times greater than RhB (Kapp = 0.05 × 106 M-1), thus influencing the rate of energy transfer. Femtosecond transient absorption reveals the observed rate constant of singlet energy transfer (kEnT) is an order-of-magnitude greater for RoseB (kEnT = 1 × 1011 s-1) than for RhB and RhB-NCS. In addition to energy transfer, each acceptor had a subpopulation of molecules (∼30%) that underwent electron transfer as a competing pathway. Thus, the structural influence of acceptor moieties must be considered for both excited state energy and electron transfer in nanocrystal-molecular hybrids. The competition between electron and energy transfer further highlights the complexity of excited state interactions in nanocrystal-molecular complexes and the need for careful spectroscopic analysis to elucidate competitive pathways.

Truxene-linked di-coumarin-mono-corrole tetrad: Synthesis, photophysical properties and application in Triplet−Triplet annihilation upconversion

Triplet−triplet annihilation upconversion (TTA-UC) has drawn widespread interest because of its great potential applications. However, it is still a challenge to design and synthesize efficient triplet photosensitizers without heavy atoms for TTA-UC. In this work, a triplet photosensitizer tetrad 2C-T-Cor based on two coumarin moieties and one corrole moiety with a truxene as the bridge was synthesized and used in TTA-UC as a novel heavy atom-free organic photosensitizer (perylene bisimide (PBI) was used as triplet acceptor). The photophysical properties were investigated by means of steady-state UV–Vis absorption and fluorescence spectroscopy, nanosecond time-resolved transient absorption spectroscopy, three-dimensional excitation emission matrix fluorescence spectra, and cyclic voltammetry. With photo-excitation of the coumarin unit at 420 nm, the intramolecular singlet–singlet energy transfer takes place from the coumarin moiety to the corrole unit with a transfer efficiency of 63.9%. Electrochemical study indicated that the intramolecular electron transfer was thermodynamically prohibited in toluene owing to the positive ΔGCS for charge-separation. A triplet excited state was investigated for 2C-T-Co via nanosecond time-resolved transient absorption and the triplet lifetime is 118 μs. 2C-T-Co can act as the triplet photosensitizer for the application of TTA-UC, and the upconversion quantum yield of 0.98% was observed.

Truxene-linked coumarin-corrole triad: Synthesis, photophysical properties and application in Triplet−Triplet annihilation upconversion

It is crucial to develop organic triplet photosensitizers (PSs) with excellent performance for upconversion applications. Herein, we synthesized a novel truxene-linked coumarin-corrole triads (C-Trux-Corr) and investigated the photophysical properties by steady-state UV–Vis absorption and fluorescence spectroscopies as well as nanosecond time-resolved transient absorption spectroscopy. The triad displays an efficient intramolecular singlet energy transfer from coumarin moiety to the corrole moiety. Nanosecond time-resolved transient difference absorption spectra indicate that the triplet excited states of C-Trux-Corr are distributed on the corrole moiety. The triplet lifetimes of C-Trux-Corr and Trux-C are 195.2 μs and 45.9 μs, respectively. The triplet state lifetime of C-Trux-Corr is significantly prolonged and it was applied as an organic triplet photosensitizer in the triplet-triplet upconversion system with an upconversion quantum yield of 2.93%, which is higher than that the corrole itself (1.27%) by more than 2-fold.

Surface energetics mediated charge transfer and exciton transfer in cation-adsorbed rubrene/PbS nanocrystal hybrids

Organic molecule and inorganic nanocrystal (NC) hybrids have become a promising platform for photon energy conversion. Although surface energetics modification has proven effective in promoting triplet energy transfer, singlet energy transfer and charge transfer have been barely investigated. Here, we systematically clarify the photophysical dynamics of charge, singlet exciton, and triplet exciton within the energy conversion process based on hybrids of rubrene and Cd2+-adsorbed PbS NCs. It is found that a considerable number of charges in rubrene molecules can be transferred to cation-induced surface states in the ∼2 ps time scale with high efficiency to trigger a delayed biexciton effect, which provides a novel approach to uncover the intermediate role of NC surface states. For the triplet exciton, strong interaction with surface states is investigated with a recycling energy transfer of around 14% efficiency, which is found to be insensitive to changes in NC surface energetics. As a result, the maximum photoluminescence lifetime of PbS NCs was enhanced by about 38%. This work reveals the neglected photo-physical dynamics in the transfer process between organic molecules/inorganic NCs and validates the capability of the surface state in sensitization of organic charges and excitons.

Outsourcing Intersystem Crossing without Heavy Atoms: Energy Transfer Dynamics in PyridoneBODIPY-C60 Complexes.

The excited state dynamics in two fully characterized pyridoneBODIPY-fullerene complexes were investigated using time-resolved spectroscopy. Photoexcitation was initially localized on the pyridoneBODIPY chromophore. The energy was rapidly transferred to the fullerene, which subsequently underwent ISC to form a triplet state and returned the energy to the pyridoneBODIPY via triplet-triplet energy transfer. This ping-pong energy transfer mechanism resulted in efficient (>85%) overall conversion of the excited state pyridoneBODIPY constituent despite a complete lack of ISC in the pyridoneBODIPY in the absence of the fullerene partner. The small difference in attachment chemistry for the fullerene did not impact the initial singlet energy transfer. However, the N-methylpyrrolidine bridge did slow both the triplet-triplet energy transfer and the ultimate relaxation rate of the final triplet state when compared to an isoxazole-based bridge. The rates of each step were quantified, and computational predictions were used to complement the proposed mechanism and energetics. The result demonstrated efficient triplet sensitization of a strong chromophore that lacks significant spin-orbit coupling.

Directing Energy and Electron Transfer Processes in Perovskite Nanocrystals

The flow of energy and electron transfer processes in semiconductor nanocrystal based light harvesting assemblies is dictated by the nature of the excited state interactions. Surface interactions of chromophore or redox active molecule which dictate the efficiency of energy/electron transfer thus plays an important role in realizing their photocatalytic and optoelectronic applications. In this presentation we will two specific examples to show the flow of energy and electrons in CsPbBr3 nanocrystals. In the first case, the excited state interactions in the CsPbBr3-Rhodamine B (RhB) hybrid assembly are probed using photoluminescence (PL) and transient absorption measurements. PL studies reveal quenching of the CsPbBr3 emission with a concomitant enhancement of the fluorescence of RhB, indicating a singlet energy transfer mechanism. In the second case we will discuss the factors dictating the electron transfer between CsPbBr3 and surface bound viologen. The implications of electron transfer in photocatalytic applications will be discussed.