Quasi-2D Hybrid Perovskite Formation Using Benzothieno[3,2-b]Benzothiophene (BTBT) Ammonium Cations
Substantial Cesium Lead(II) Iodide Black Phase Stabilization
Paul Henry Denis (Associated lab IMOMEC, Universiteit Hasselt)
Martijn Mertens (Universiteit Hasselt, Associated lab IMOMEC)
Wouter T.M. Van Gompel (Universiteit Hasselt, Associated lab IMOMEC)
Arthur Maufort (Associated lab IMOMEC, Universiteit Hasselt)
Sigurd Mertens (Universiteit Hasselt, Associated lab IMOMEC)
Z. Wei (TU Delft - ChemE/Opto-electronic Materials)
Melissa Van Landeghem (Associated lab IMOMEC, Universiteit Hasselt)
Sam Gielen (Universiteit Hasselt, Associated lab IMOMEC)
F.C. Grozema (TU Delft - ChemE/Opto-electronic Materials)
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Abstract
3D hybrid perovskites (APbX3) have made a significant impact on the field of optoelectronic materials due to their excellent performance combined with facile solution deposition and up-scalable device fabrication. Nonetheless, these materials suffer from environmental instability. To increase material stability, the organic cation (A) is substituted by the non-volatile cesium cation. However, the desired photoactive cesium lead(II) iodide black phase is metastable in ambient conditions and spontaneously converts into the photo-inactive yellow δ-phase. In this work, the black phase is stabilized by the formation of a quasi-2D perovskite containing a benzothieno[3,2-b]benzothiophene (BTBT) large organic ammonium cation. Thermal analysis shows that degradation of the butylammonium (BA)-based quasi-2D perovskite (BA)2CsPb2I7 sets in at ≈130 °C, while (BTBT)2CsPb2I7 is phase-stable until ≈230 °C. Additionally, the (BTBT)2CsPb2I7 film does not show any sign of degradation after exposure to 77% Relative Humidity in the dark for 152 days, while (BA)2CsPb2I7 degrades in a single day. Photoconductor-type detectors based on (BTBT)2CsPb2I7 demonstrate an increased external quantum efficiency and a similar specific detectivity compared to the BA-based reference detectors. The results demonstrate the utility of employing a BTBT cation within the organic layer of quasi-2D perovskites to significantly enhance the stability while maintaining the optoelectronic performance.