Polaron and Spin Dynamics in Organic–Inorganic Lead Halide Perovskite Nanocrystals

Abstract

Long‐lived carrier population and spin‐based behavior in lead halide perovskite nanocrystals (NCs) are extremely interesting for implementing photovoltaic devices with efficiencies exceeding the Shockley–Queisser limit and quantum information processing, respectively. However, a comprehensive understanding of polaron‐mediated charge carrier interactions and an accurate description of the spin‐polarized states for spintronics are still lacking. Herein, the carrier and spin interactions are studied under controlled conditions in FAPbI3 and Cs0.01FA0.99Pb(Br0.11I0.89)3 NCs through ultrafast transient absorption (TA) spectroscopy. At early timescales, TA spectrum shows an asymmetric derivative feature originating from the hot carrier‐induced spectral redshift in FAPbI3 NCs (55 ± 3 meV) and Cs0.01FA0.99Pb(Br0.11I0.89)3 NCs (54 ± 2 meV) at the bandedges that stabilizes to 9 ± 1 and 11 ± 2 meV, respectively, at 1 ps due to the polaron formation. The kinetic analysis indicates that the polaron populations in FAPbI3 and Cs0.01FA0.99Pb(Br0.11I0.89)3 NCs decay with an average lifetime of 657 ± 34 and 532 ± 28 ps, respectively. The circular polarization‐resolved TA reveals that polaron formation can control spin relaxation in NCs, thus providing a powerful tool to explore the development of their prospective applications in spintronics.

Room-Temperature Anomalous Coherent Excitonic Optical Stark Effect in Metal Halide Perovskite Quantum Dots

“…30−33 Their low-cost solution processability and ease of integration with an existing nanofabrication facility make them much more attractive. 34,35 Moreover, their strong band-edge exciton− photon coupling, 36 defect-tolerant electronic structure of a trap-free nature, 34,35,37−39 discrete and narrow-bandwidth exciton transitions, 5,11,39 and scalable production of highly coherent quantum emitters 37,40 make them an ideal candidate for the study of coherent and spin-selective light−matter interactions at room temperature. In addition, the multiexciton interactions in MHP QDs, in particular, CsPbBr 3 , are reasonably strong 32,41 and thus can influence the coherent light−matter interactions.…”

Photoinduced large polaron transport and dynamics in organic–inorganic hybrid lead halide perovskite with terahertz probes

“…A number of spectroscopic and optical measurements, such as time-resolved optical Kerr effect spectroscopy, time-resolved two-photon photoemission, transient reflectance, and absorption spectroscopies, time-domain Raman spectroscopy, angle-resolved photoelectron spectroscopy, have been used to reveal the electron-phonon (e-ph) coupling in CsPbBr 3 [32][33][34] , MAPbBr 3 [35][36][37] , and MAPbI 3 [38][39][40][41][42] . However, these measurements are associated with the large polaron formation either from the phonon or from the electronic structure perspective [42][43][44] (See Supplementary Table S1 for a literature survey). In addition, it is challenging, to use an ultrafast spectroscopic technique in the visible region to access the polaron mobility, carrier scattering parameters, and dynamics in MHPs quantitatively, which are considered as the fundamental nature of the large polaron 29,45 .…”

Spatiodynamics, Photodynamics, and Their Correlation in Hybrid Perovskites

“…For free carriers, several studies have suggested that the carriers be transferred to spatially localized states arising from interacting electrons and phonons, known as polarons. Such a polaron formation can protect the free carriers (electrons and holes) from recombination, eventually elongating the carrier lifetime. − Recent experiments have shown a correlation between the rotation dynamics of organic cations and carrier lifetime for 3D perovskites, suggesting that the rotation dynamics of cations can promote the formation and stabilization of polarons. ,,− Specifically, the monocationic charge on MA is localized on the −NH 3 + group and forms a cationic rotor in the PbI 3 – cage. In this case, the free carriers attract/repel multiple cations in their proximity presumably via electrostatic interaction and wavefunction overlapping, leading to a polaron consisting of a carrier–multi-ion entity (Figure b).…”