Rational alloying of secondary and aromatic ammonium cations in a metal-halide perovskite toward crystal-array photodetection

Two-dimensional (2D) hybrid perovskites with the Ruddlesden-Popper lattice (A′)2(A)n−1MnX3n+1 are emerging as the promising optoelectronic candidates, both the inorganic and organic ingredients of which can be tailored to modulate the physical properties. Nevertheless, there is a scarcity of 2D multilayered motifs with the A-site large-size cations occupying perovskite cavities. Here, by rational mixed-cation alloying, we present a new 2D hybrid perovskite, (4-TFBMA)2(DMA)Pb2I7 (1), in which the secondary cation of CH3NH2CH3+ (DMA) is located inside the perovskite cage while the aromatic 4-(trifluoromethyl)benzylammonium (4-TFBMA) cation acts as a spacer moiety. Benefiting from the quantum structure of alternating organic spacers and inorganic networks, crystal-array detectors of 1 show fascinating in-plane photodetection responses of large detectivity (−2.95 × 1012 Jones) and responsivity (−1.97 A W−1), comparable to those of some inorganic 2D counterparts. In addition, a fast response rate (−264 µs) and a low dark current are also realized, related to the high crystalline quality and suppression of the hopping barrier due to the insulating organic spacing layers. This result sheds light on the further exploration of new 2D hybrid perovskites toward high-performance photodetector applications.