Shape-Tunable Charge Carrier Dynamics at the Interfaces between Perovskite Nanocrystals and Molecular Acceptors

Abstract

Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.

Tuning Charge Carrier Dynamics and Surface Passivation in Organolead Halide Perovskites with Capping Ligands and Metal Oxide Interfaces

“…For all samples, the main spectral feature is a negative signal peaking near the absorption band edge. [4a,27] Previous reports have assigned similar features in organolead halide perovskites to ground‐state bleaching (GSB) resulting from state filling close to the band edges, preventing subsequent absorption at these energies. At early times (<1 ps), we observe a positive photoinduced absorption signal at longer wavelengths than the GSB, previously attributed to bandgap renormalization and subsequent carrier cooling .…”

“…Our TAS measurements also revealed a broad photoinduced absorption near 700 nm, where similar signals have been assigned as a signature for excitons in iodide and bromide organolead halide perovskites. [27b,34] We calculated the ratios of absorbance changes in the 700–740 nm range to the GSB to quantify the exciton population relative to the total excited species in the different samples (Figure S10, Supporting Information). A more significant exciton signal is observed for the nanostructured samples compared to Bulk MAPbBr 3 , consistent with the increased effective charge carrier density leading to a higher proportion of excitons.…”

Optical studies of semiconductor perovskite nanocrystals for classical optoelectronic applications and quantum information technologies: a review

“…The charge migration rate and diffusion length of CsPbBr 3 NC films were estimated by Yettapu et al 90 to be ∼4500 cm 2 V −1 s −1 and ∼9.2 μm, respectively, which are on a par with or even surmount those values possessed by their counterpart bulk single crystals and films. [91][92][93][94][95] Meanwhile, it takes 0.1 to 100 ps for the photoexcited electrons or holes to be transferred from perovskite NCs to the surrounding organic molecules, [96][97][98][99] resulting in a charge-separation state that can persist even after several microseconds. 100 While this charge-separation state is beneficial for realizing efficient charge extraction in photovoltaics, it can be further extended to the photocatalytic and light-harvesting applications according to a recent study by Dana et al 101 on the charge transfer process between perovskite CsPbBr 3 and traditional CdSe NCs.…”

Tuning Hole and Electron Transfer from Photoexcited CdSe Quantum Dots to Phenol Derivatives: Effect of Electron‐Donating and ‐Withdrawing Moieties

“…However,b efore monitoring the excited-state properties, it is imperative to study the ground-statei nteraction between CdSe QDs and pure phenol, 4NP,o r4 MP molecules. [58,59] However,i tc an be observed that at relativelyl ow concentrationsb oth composites shows similar quenching rates;t he quenching mechanism is mainly diffusion controlled, as the availability of interactings urrounding phenol molecules to the CdSe QD surfaced ecreases. Steady-state emission studies of the synthesized CdSe QDs have been carriedo ut after the addition of phenol derivatives.…”