Third-Order Optical Nonlinearities in Organometallic Methylammonium Lead Iodide Perovskite Thin Films

Abstract

With solar conversion efficiencies surpassing 20%, organometallic perovskites show tremendous promise for solar cell technology. Their high brightness has also led to demonstrations of lasing and power-efficient electroluminescence. Here we show that thin films of methylammonium lead iodide, prepared by solution processing at temperatures not exceeding 100 °C, exhibit a highly nonlinear intensity-dependent refractive index due to changes in the free-carrier concentration and for femtosecond excitation at higher intensities undergo saturation that can be attributed to the Pauli blocking effect. Nonlinear refractive index and nonlinear absorption coefficients were obtained by the Z-scan technique, performed simultaneously in open- and closed-aperture configurations. Both nanosecond- and femtosecond-pulsed lasers at multiple wavelengths were used in order to distinguish between the mechanisms inducing the nonlinearities. The magnitude and sign of the nonlinear refractive index n 2 were determined. For resonant excitation, free carrier generation is the dominant contribution to the nonlinear refractive index, with a large nonlinear refractive index of n 2 = 69 × 10–12 cm2/W being observed for resonant femtosecond pumping and n 2 = 34.4 × 10–9 cm2/W for resonant nanosecond pumping. For nonresonant femtosecond excitation, bound-charge-induced nonlinearity leads to n 2 = 36 × 10–12 cm2/W. These values are equivalent to the best reported metrics for conventional semiconductors, suggesting that organometallic perovskites are promising materials for optical switching and bistability applications.

Photonics and Optoelectronics of 2D Metal‐Halide Perovskites

“…However, the third‐order nonlinear processes, in principle, are allowed in all materials. It was recently estimated that the nonlinear refractive index in CH 3 NH 3 PbI 3 could be ≈36 × 10 −12 cm 2 W −1 for nonresonant femtosecond excitation, and the third‐order nonlinear susceptibility in CH 3 NH 3 PbBr 3 could be 1.6 ± 1.0 × 10 −6 esu, which have the same order of magnitude as observed for the semiconductors that are typically used in optical switches such as GaAs and Si.…”

“…There are previous encouraging reports about nonlinearities in various types of metal‐halide perovskites . Perovskite semiconductor NC films have demonstrated the potentials to tackle current challenges such as the two‐photon‐based pumped lasers and optical modulations.…”

Room temperature three-photon pumped CH3NH3PbBr3 perovskite microlasers

“…The ferroelectric character can also induce quantum coherent wave propagation of exciton, which leads to more efficient charge extraction7. Interestingly, such kind of ferroelectric properties of hybrid lead halide perovskites also make them to be comparable to the other ferroelectric materials such as lithium niobate89101112. Consequently, the nonlinear optical properties can be expected in the hybrid lead halide perovskites.…”

“…Within past two years, a number of nonlinear effects have been experimentally demonstrated, e.g. two-photon absorption8910, two-photon pumped photoluminescence (PL)8, two-photon pumped amplified spontaneous emission (ASE)13, and two-photon pumped lasers14. Very recently, three-photon pumped PL and amplifications have also been reported15.…”

Photorefractive Effect in Organic–Inorganic Hybrid Perovskites and Its Application to Optical Phase Shifter

“…This interference-detection system enables us to measure even slight changes in the refractive index by analyzing the phase shift of the interference signal. [34,35] To understand the origin of this refractive-index change, we measured the dependence of the phase shift on the pumppulse fluence. Here, the periodic structure along the vertical axis is a result from sequential on/off switching of the pump pulse via an optical chopper at 4 Hz.…”