*Article* **Temperature-Responsive Photoluminescence and Elastic Properties of 1D Lead Halide Perovskites** *R***- and** *S***-(Methylbenzylamine)PbBr<sup>3</sup>**

**Rui Feng <sup>1</sup> , Jia-Hui Fan <sup>2</sup> , Kai Li <sup>2</sup> , Zhi-Gang Li <sup>2</sup> , Yan Qin <sup>3</sup> , Zi-Ying Li <sup>2</sup> , Wei Li 2,\* and Xian-He Bu 1,2**


**Abstract:** Low-dimensional metal halide perovskites (MHPs) have received much attention due to their striking semiconducting properties tunable at a molecular level, which hold great potential in the development of next-generation optoelectronic devices. However, the insufficient understanding of their stimulus-responsiveness and elastic properties hinders future practical applications. Here, the thermally responsive emissions and elastic properties of one-dimensional lead halide perovskites *R*- and *S*-MBAPbBr<sup>3</sup> (MBA<sup>+</sup> = methylbenzylamine) were systematically investigated via temperaturedependent photoluminescence (PL) experiments and first-principles calculations. The PL peak positions of both perovskites were redshifted by about 20 nm, and the corresponding full width at half maximum was reduced by about 40 nm, from ambient temperature to about 150 K. This kind of temperature-responsive self-trapped exciton emission could be attributed to the synergistic effect of electron–phonon coupling and thermal expansion due to the alteration of hydrogen bonding. Moreover, the elastic properties of *S*-MBAPbBr<sup>3</sup> were calculated using density functional theory, revealing that its Young's and shear moduli are in the range of 6.5–33.2 and 2.8–19.5 GPa, respectively, even smaller than those of two-dimensional MHPs. Our work demonstrates that the temperatureresponsive emissions and low elastic moduli of these 1D MHPs could find use in flexible devices.

**Keywords:** low-dimensional; metal halide perovskite; photoluminescence; stimulus-responsive; elastic property
