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

Abstract

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 (K app = 9.4 × 106 M–1) 200 times greater than RhB (K app = 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 (k EnT = 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.

Enhanced Stability and Energy Transfer in Perovskite Nanocrystals: Paving the Way for Moisture-Resistant Light-Harvesting Devices

“…The significant PL quenching of the donor indicates the presence of excited-state interactions (either electron or energy transfer) between the D–A pairs. It is worth noting that the redox potential of RITC (−0.6 V vs NHE) is lower than the conduction band of the PNCs (−0.87 V vs NHE), suggesting the possibility of electron transfer as a potential deactivation pathway. , Singlet and triplet energy transfer processes are also thermodynamically favorable in perovskite-dye assemblies of this nature. − Therefore, a comprehensive spectroscopic investigation is required to determine which of these processes is operating for each D–A pair.…”

Singlet Sensitization of a BODIPY Rotor Triggered by Marriage with Perovskite Nanocrystals

“…They can participate in energy or charge transfer (CT) processes according to the excitation energy, the spectral overlap between the donor and the acceptor, and their redox potentials. [1][2][3][4] DOI: 10.1002/adom. 202300138 In most of the reported examples, excitation of lead halide perovskite (LHP) in a hybrid LHP NC−organic chromophore assembly results in triplet energy transfer (ET) to the organic chromophore, while the singlet ET process is rarely observed.…”

“…There are only two examples of singlet energy transfer from perovskite NCs to dyes, specifically from CsPbBr 3 NCs to Rhodamine derivatives and Rose Bengal as acceptor molecules. [2,3] Here, we explore the remarkable potential of colloidal CsPbBr 3 NCs to operate as singlet sensitizers of a meso-(4-carboxyphenyl) BODIPY molecular rotor, specifically 8-(4-carboxyphenyl)-4,4difluoro-4-bora-3a,4a-diaza-s-indacene (C-BPY), and how quantum confinement and surface ligand engineering can modulate their efficiency in the singlet sensitization and determine the localization of the acceptor chromophore. Such efficiency is systematically studied here considering the NC size, the nature of the capping ligands, and the spectral overlap integral between the donor and the acceptor.…”

“…They can participate in energy or charge transfer (CT) processes according to the excitation energy, the spectral overlap between the donor and the acceptor, and their redox potentials. [ 1–4 ]…”

“…There are only two examples of singlet energy transfer from perovskite NCs to dyes, specifically from CsPbBr 3 NCs to Rhodamine derivatives and Rose Bengal as acceptor molecules. [ 2,3 ]…”