Spectrally Resolved Ultrafast Exciton Transfer in Mixed Perovskite Quantum Wells

Abstract

Solution-processed perovskite quantum wells have been used to fabricate increasingly efficient and stable optoelectronic devices. Little is known about the dynamics of photogenerated excitons in perovskite quantum wells within the first few hundred femtosecondsa crucial time scale on which energy and charge transfer processes may compete. Here we use ultrafast transient absorption and two-dimensional electronic spectroscopy to clarify the movement of excitons and charges in reduced-dimensional perovskite solids. We report excitonic funneling from strongly to weakly confined perovskite quantum wells within 150 fs, facilitated by strong spectral overlap and orientational alignment among neighboring wells. This energy transfer happens on time scales orders of magnitude faster than charge transfer, which we find to occur instead over 10s to 100s of picoseconds. Simulations of both Förster-type interwell exciton transfer and free carrier charge transfer are in agreement with these experimental findings, with theoretical exciton transfer calculated to occur in 100s of femtoseconds.

Optimization of Low‐Dimensional Components of Quasi‐2D Perovskite Films for Deep‐Blue Light‐Emitting Diodes

“…For P2 film, the strongest GSB was located at 396 nm (n 1 domain) with ultralong bleaching delay of 78 ps (Figure S7, Supporting Information). It has been confirmed that excitation relaxation and exciton transfer in 2D perovskite films occur within initial stages (i.e., from ≈0.1 to ≈10 ps) while emission occurs after 10s ps . However, we did not found any steady PL signal from n 1 domain (Figure S8, Supporting Information).…”

“…Domain distribution and formation dynamics in quasi‐2D perovskite films are demonstrated highly sensitive to spacer cations . Remarkably, a mixed spacer system was set up to significantly modulate the component of quasi‐2D perovskite films .…”

Dimension control of in situ fabricated CsPbClBr2 nanocrystal films toward efficient blue light-emitting diodes

“…The evolutions of the peak and FWHM illustrate the continuous competition of bleach signals from different n value domains. In stage II, an ultrafast exciton transfer from small-n domains (n ≤ 3) to large-n domains (n ≥ 4) occurs in the time span of 0.7-1.3 ps 39,40,50,51 , resulting in a fast redshift of the broadened bleach peak. In stage III, excitons begin to dissociate into free charge carriers and charge transfer occurs subsequently within a few picoseconds [51][52][53][54][55] , which induces a further redshift of the bleach peak.…”

Efficient interlayer exciton transport in two-dimensional metal-halide perovskites

“…phases of different n) using time resolved spectroscopy. 13,33 This downhill energy transfer process is of particular relevance in hybrid 2D-3D perovskite solar cells, where phases of distinct n co-exist. 15 The transfer between perovskite layers of identical thickness, however, has not been studied yet.…”