Femtosecond optical nonlinearities and ultrafast absorption dynamics of colloidal 2D organometal halide ((C12H25-NH3)2PbI4) nanoparticles and thin films

Layered 2D Inorganic-Organic (IO) hybrid semiconductors of the type (R-NH3)(2)PbI4 have shown tremendous potential applications in various photonics and optoelectronic devices. In this work, femtosecond laser induced optical nonlinearities and excited state charge carrier dynamics of organometal halide (C12H26-NH3)(2)PbI4 (C12PI) 2D colloidal nanoparticles (NPs) and the thin film counterpart are investigated. These colloidal 2D NPs of sizes similar to 9 nm, show third-order optical nonlinearity having two-photon absorption coefficient (2PA) (beta similar to 26 -23 cm/GW) and positive nonlinear refractive index (n(2)similar to 7.6 x 10(-2) cm(2)/GW), while thin films show beta similar to 78-134 cm/GW and n(2)similar to 0.003-0.2 x 10(-2) cm(2)/GW. The origins of two-photon induced absorption and Kerr-type refractive nonlinearity are as a result of induced molecular polarization and charge transfer effects between organic cation (C12H26-NH3)(+) and inorganic anion (PbI6 octahedra). The ultrafast transient absorption spectral studies demonstrate the room-temperature Mott-type exciton excited-state charge carrier dynamics and charge carrier recombination features. The laser pump intensity dependent transient absorption spectral (TAS) features reveal wide information about ground state bleaching (GSB similar to 510 nm, Delta A<0 with decay of 28.2-3.2 ps) along with a photo-induced absorption (PIA similar to 476 nm, Delta A>0, with decay of 22-6.3 ps) regions. The systematic studies of optical nonlinearities and ultrafast absorption dynamics of 2D IO hybrid semiconductor colloidal nanoparticles and thin film will provide a new platform for advanced photonics and ultrafast optical switching devices applications.

Automated summary

This study investigates the optical properties and charge carrier dynamics of 2D inorganic-organic hybrid semiconductors, revealing their strong nonlinear optical characteristics and ultrafast absorption dynamics, which are of great importance in developing advanced photonics and optical switching devices.