Morrow Darien J, Hautzinger Matthew P, Lafayette David P, Scheeler Jason M, Dang Lianna, Leng Meiying, Kohler Daniel D, Wheaton Amelia M, Fu Yongping, Guzei Ilia A, Tang Jiang, Jin Song, Wright John C
Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States.
Sargent Joint Research Center, Wuhan National Laboratory for Optoelectronics (WNLO), School of Optical and Electronic Information, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, 430074 Hubei, P.R. China.
J Phys Chem Lett. 2020 Aug 20;11(16):6551-6559. doi: 10.1021/acs.jpclett.0c01720. Epub 2020 Jul 31.
Layered two-dimensional Ruddlesden-Popper (RP) halide perovskites are an intriguing class of semiconductors being explored for their linear and nonlinear optical and ferroelectric properties. Second harmonic generation (SHG) is commonly used to screen for noncentrosymmetric and ferroelectric materials. However, SHG measurements of perovskites can be obscured by their intense multiphoton photoluminescence (mPL). Here, we apply multidimensional harmonic generation as a method to eliminate the complications from mPL. By scanning and correlating both excitation and emission frequencies, we unambiguously assess whether a material supports SHG by examining if an emission feature scales as twice the excitation frequency. Measurements of a series of = 2, 3 RP perovskites reveal that, contrary to previous belief, -butylammonium (BA) RP perovskites are not SHG-active and thus centrosymmetric, but RP perovskites with phenylethylammonium (PEA) and 2-thiophenemethylammonium (TPMA) spacer cations display SHG. This work establishes multidimensional harmonic generation as a definitive method to measure SHG in halide perovskites.
层状二维Ruddlesden-Popper（RP）卤化物钙钛矿是一类引人关注的半导体，因其线性和非线性光学以及铁电特性而受到研究。二次谐波产生（SHG）通常用于筛选非中心对称和铁电材料。然而，钙钛矿的SHG测量可能会被其强烈的多光子光致发光（mPL）所掩盖。在此，我们应用多维谐波产生作为一种消除mPL带来的复杂性的方法。通过扫描并关联激发和发射频率，我们通过检查发射特征是否按激发频率的两倍缩放来明确评估一种材料是否支持SHG。对一系列n = 2、3的RP钙钛矿的测量表明，与先前的看法相反，丁基铵（BA）RP钙钛矿不具有SHG活性，因此是中心对称的，但具有苯乙铵（PEA）和2-噻吩甲基铵（TPMA）间隔阳离子的RP钙钛矿显示出SHG。这项工作确立了多维谐波产生作为测量卤化物钙钛矿中SHG的一种确定性方法。
