Tuning Hot Carrier Cooling Dynamics by Dielectric Confinement in Two-Dimensional Hybrid Perovskite Crystals

• Published in: ACS nano 2019-11, Vol.13 (11), p.12621-12629
• Main Authors: Yin, Jun, Maity, Partha, Naphade, Rounak, Cheng, Bin, He, Jr-Hau, Bakr, Osman M, Brédas, Jean-Luc, Mohammed, Omar F
• Format: Article
• Language: English
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.9b04085

Hot carrier (HC) cooling is a critical photophysical process that significantly influences the optoelectronic performance of hybrid perovskite-based devices. The hot carrier extraction at the device interface is very challenging because of its ultrashort lifetime. Here, ultrafast transient reflectance spectroscopy measurements and time-domain ab initio calculations show how the dielectric constant of the organic spacers can control and slow the HC cooling dynamics in single-crystal 2D Ruddlesden–Popper hybrid perovskites. We find that (EA)2PbI4 (EA = HOC2H4NH3 +) that correspond to a high dielectric constant organic spacer has a longer HC cooling time compared to that of (AP)2PbI4 (AP = HOC3H6NH3 +) and (PEA)2PbI4 (PEA = C6H5C2H4NH3 +). The slow HC relaxation process in the former case can be ascribed to a stronger screening of the Coulomb interactions, a small nonradiative internal conversion within the conduction bands, as well as a weak electron–phonon coupling. Our findings provide a strategy to prolong the hot carrier cooling time in low-dimensional hybrid perovskite materials by using organic spacers with reduced dielectric confinement.