2D and quasi-2D metal halide perovskites for optoelectronic device applications

Abstract

Metal halide perovskite materials demonstrate immense potential for photovoltaic and electronic applications. In particular, 2D layered metal halide perovskites have advantages over their 3D counterparts for optoelectronic applications of structural stability and structural diversity, extending the range of tunable optoelectronic properties.

The first part of the thesis focuses on 2D RP X-site substituted phase Cs2Pb(SCN)2Br2 perovskite. When reporting, it was the first inorganic cation pseudo-halide perovskite single crystal synthesized. This 2D single crystal has a space group of Pmmn at room temperature but at 450K exhibits a reversible first-order phase transformation to 3D CsPbBr3. It has a low exciton binding energy of 66meV, exceptional for a 2D perovskite. A Cs2Pb(SCN)2Br2 single-crystal photodetector is demonstrated with a respectable responsivity of 8.46mA/W and detectivity of ≈1.2×1010Jones at 0.5V.

The second part of the thesis reports piperidine and pyridine series DJ phase tin perovskites, including the first report of 3AMPSnI4 and 3AMPYSnI4 single crystals. The relationships between crystal structures, material strain, optical bandgap and charge extraction capability were studied. 4AMPSnI4 was demonstrated to be suitable for field-effect transistor application producing respectable device mobility of 0.57cm2/Vs.

Finally, the thesis demonstrated a q-2D ACI phase GAMA5Pb5I16 perovskite solar cells consuming 3 to 4 times less solvent and improving working device yield from 25% to 80% compared to the conventional anti-solvent method. For the first time, monolithic perovskite-silicon tandem solar cells using ACI phase q-2D perovskites showed excellent thermal stability passing the IEC 61215 standard Thermal Cycling test twice. For the first time, radiation tolerance of q-2D perovskites cells is also evaluated. They demonstrate excellent durability under 7MeV protons up to the fluence of 1013p/cm2, showing their potential for space applications.