Li Bingyue, Li Hui, Sun Yanhui, Humphrey Mark G, Zhang Chi, Huang Zhipeng
School of Chemical Science and Engineering, Tongji University, Shanghai 200092, P. R. China.
Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
ACS Appl Mater Interfaces. 2023 Mar 1;15(8):10858-10867. doi: 10.1021/acsami.2c23266. Epub 2023 Feb 20.
Lead-free perovskites have attracted increasing attention because they can address the toxicity and instability problems inherent to lead-halide perovskites. Furthermore, the nonlinear optical (NLO) properties of lead-free perovskites are rarely explored. Herein, we report significant NLO responses and defect-dependent NLO behavior of CsAgBiBr. Specifically, a thin film of pristine CsAgBiBr exhibits strong reverse saturable absorption (RSA), while a film of CsAgBiBr with defects (denoted as CsAgBiBr(D)) shows saturable absorption (SA). The nonlinear absorption coefficients are ca. 4.0 × 10 cm GW (515 nm laser excitation) and 2.6 × 10 cm GW (800 nm laser excitation) for CsAgBiBr and -2.0 × 10 cm GW (515 nm laser excitation) and -7.1 × 10 cm GW (800 nm laser excitation) for CsAgBiBr(D). The optical limiting threshold of CsAgBiBr is 8.1 × 10 J cm (515 nm laser excitation). The samples show excellent long-term performance stability in air. The RSA of pristine CsAgBiBr correlates with excited-state absorption (515 nm laser excitation) and excited-state absorption following two-photon absorption (800 nm laser excitation), while the defects in CsAgBiBr(D) strengthen the ground-state depletion and Pauli blocking, resulting in SA.
无铅钙钛矿因其能够解决卤化铅钙钛矿固有的毒性和不稳定性问题而受到越来越多的关注。此外，无铅钙钛矿的非线性光学（NLO）性质鲜有研究。在此，我们报道了CsAgBiBr显著的NLO响应和与缺陷相关的NLO行为。具体而言，纯净的CsAgBiBr薄膜表现出强烈的反饱和吸收（RSA），而有缺陷的CsAgBiBr薄膜（记为CsAgBiBr(D)）则表现出饱和吸收（SA）。对于CsAgBiBr，非线性吸收系数在515 nm激光激发下约为4.0×10 cm GW，在800 nm激光激发下约为2.6×10 cm GW；对于CsAgBiBr(D)，在515 nm激光激发下为 -2.0×10 cm GW，在800 nm激光激发下为 -7.1×10 cm GW。CsAgBiBr的光限幅阈值为8.1×10 J cm（515 nm激光激发）。这些样品在空气中表现出优异的长期性能稳定性。纯净的CsAgBiBr的RSA与激发态吸收（515 nm激光激发）以及双光子吸收后的激发态吸收（800 nm激光激发）相关，而CsAgBiBr(D)中的缺陷增强了基态耗尽和泡利阻塞，从而导致SA。
