Enhanced nonlinear optical performance of perovskite films passivated by porphyrin derivatives

Ionic defects generated from the grain boundaries and surfaces of perovskite films are primary factors that degrade the nonlinear optical (NLO) properties, and therefore filling or eliminating these defects is crucial for achieving high-performance NLO devices. Herein, a new passivation strategy is proposed via binding the functional groups of porphyrins with the defects of perovskite films. A series of porphyrin-modified perovskite films were successfully constructed and exhibited significantly enhanced optical nonlinearity in broadband regions and temporal domains, compared with the pristine CH₃NH₃PbI₃ perovskite film. In particular, the corresponding NLO absorption coefficient (β) of MAPbI₃/ZnP3 (β = 116.65 cm GW⁻¹) at 800 nm in the femtosecond (fs) regime is one order of magnitude larger than that of the pristine CH₃NH₃PbI₃ perovskite film (β = 6.09 cm GW⁻¹), which can be ascribed to the increased photo-induced ground state dipole moment of the passivated perovskite during the two-photon absorption (TPA) process and the photo-induced electron/energy transfer between the porphyrin and perovskite. In the nanosecond (ns) regime, all modified samples showed prominent reverse saturable absorption (RSA) at 1064 nm and saturable absorption (SA) at 532 nm determined by their free carrier absorption and band-filling effect, respectively. These observations strongly confirm that the passivation strategy through the effective coordination interaction between porphyrin functional groups and perovskite defects can considerably improve the NLO performance of perovskite materials. Our work affords a feasible paradigm for developing adaptable perovskite photonic devices in diverse laser pulse width and wavelength regions.