Temperature-Dependent Structural and Optoelectronic Properties of the Layered Perovskite 2‑Thiophenemethylammonium Lead Iodide

Improved knowledge of the influence of temperature upon
layered
perovskites is essential to enable perovskite-based devices to operate
over a broad temperature range and to elucidate the impact of structural
changes upon the optoelectronic properties. We examined the Ruddlesden–Popper
layered perovskite 2-thiophenemethylammonium lead iodide (ThMA2PbI4) and observed a structural phase transition
between a high- and a low-temperature phase at 220 K using
temperature-dependent X-ray diffraction, UV–visible absorption,
and photoluminescence (PL) spectroscopy. The structural phase transition
altered the tilt pattern of the inorganic octahedra layer, modifying
the absorption and PL spectra. Further, we found a narrow and intense
additional PL peak in the low-temperature phase, which we assigned
to radiative emission from a defect-bound exciton state. In both phases
we determined the thermal expansion coefficient and found values similar
to those of cubic 3D perovskites, i.e., larger than those of typical
substrates such as glass. These results demonstrate that the organic
spacer plays a critical role in controlling the temperature-dependent
structural and optoelectronic properties of layered perovskites and
suggests more widely that strain management strategies may be needed
to fully utilize layered perovskites in device applications.