Speaker
Description
n=1 two-dimensional (2D) perovskites display narrow absorption due to their excitonic nature and quantum-confined structure. They offer a compelling route to filter-free, narrowband photodetection compared with broadband 3D counterparts. While halide mixing provides spectral tunability, it introduces severe phase segregation and energetic disorder. Current understanding of this phenomenon is derived mainly from static material characterisation, leaving its dynamic impact in operational devices unexplored. Herein, we bridge this gap by integrating n = 1 (PEA)2PbBrxI4-x into photoconductors, achieving tunable response from 402 to 516 nm, with the highest specific detectivity (D) of 2.11×10^11 Jones at 20V. We demonstrate that halide immiscibility significantly reduces D. We reveal how crystal packing drives phase segregation with DFT calculations and applied spectroscopies to understand the energetic disordering. Chloride additives are found to suppress macroscopic segregation and improve crystallinity, however, electronic disorder is simultaneously worsened, introducing traps that quench photocurrent. Directly visualised via photocurrent mapping and kelvin probe force microscopy. Consequently, the additive enhances the out-of-plane orientation, disrupting in-plane transport in photoconductors, while improving performance in vertical photodiodes. This work provides the first device-level insight into halide immiscibility in n=1 2D perovskites, revealing that overcoming the performance limitations in these systems requires balancing long-range structural order with short-range electronic integrity.
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