Advances in physicochemical characterization of lead-free hybrid perovskite [NH3(CH2)3NH3]CuBr4 crystals

To support the development of eco-friendly hybrid perovskite solar cells, structural, thermal, and physical properties of the lead-free hybrid perovskite [NH 3 (CH 2 ) 3 NH 3 ]CuBr 4 were investigated using X-ray diffraction (XRD), differential scanning calorimetry, thermogravimetric analysis, and nuclear magnetic resonance spectroscopy. The crystal structure confirmed by XRD was monoclinic, and thermodynamic stability was observed at approximately 500 K without any phase transition. The large changes in the 1 H chemical shifts of NH 3 and those in C2 close to N are affected by N–H∙∙∙Br hydrogen bonds because the structural geometry of CuBr 4 changed significantly. The 1 H and 13 C spin–lattice relaxation times (T 1ρ ) showed very similar molecular motions according to the Bloembergen–Purcell–Pound theory at low temperatures; however, the 1 H T 1ρ values representing energy transfer were about 10 times lesser than those of 13 C T 1ρ . Finally, the 1 H and 13 C T 1ρ values of [NH 3 (CH 2 ) 3 NH 3 ] Me Br 4 ( Me = Cu, Zn, and Cd) were compared with those reported previously. 1 H T 1ρ was affected by the paramagnetic ion of the anion, while 13 C T 1ρ was affected by the Me Br 4 structure of the anion; 13 C T 1ρ values in Me = Cu and Cd with the octahedral Me Br 6 structure had longer values than those in Me = Zn with the tetrahedral Me Br 4 structure. We believe that these detailed insights on the physical properties will play a crucial role in the development of eco-friendly hybrid perovskite solar cells.