Quasi-2D Hybrid Perovskite Formation Using Benzothieno3,2-bBenzothiophene (BTBT) Ammonium Cations: Substantial Cesium Lead(Ⅱ) Iodide Black Phase Stabilization

摘要

3D hybrid perovskites (APbX_3) have made a significant impact on the field ofoptoelectronic materials due to their excellent performance combined withfacile solution deposition and up-scalable device fabrication. Nonetheless,these materials suffer from environmental instability. To increase materialstability, the organic cation (A) is substituted by the non-volatile cesiumcation. However, the desired photoactive cesium lead(Ⅱ) iodide black phaseis metastable in ambient conditions and spontaneously converts into thephoto-inactive yellow δ-phase. In this work, the black phase is stabilizedby the formation of a quasi-2D perovskite containing a benzothieno[3,2-b]benzothiophene (BTBT) large organic ammonium cation. Thermal analysisshows that degradation of the butylammonium (BA)-based quasi-2D perovskite(BA)_2CsPb_2I_7 sets in at ≈130 ℃, while (BTBT)_2CsPb_2I_7 is phase-stableuntil ≈230 ℃. Additionally, the (BTBT)_2CsPb_2I_7 film does not show any sign ofdegradation after exposure to 77% Relative Humidity in the dark for 152 days,while (BA)_2CsPb_2I_7 degrades in a single day. Photoconductor-type detectorsbased on (BTBT)_2CsPb_2I_7 demonstrate an increased external quantum efficiencyand a similar specific detectivity compared to the BA-based referencedetectors. The results demonstrate the utility of employing a BTBT cationwithin the organic layer of quasi-2D perovskites to significantly enhance thestability while maintaining the optoelectronic performance.