Abstract
Not until recently have metal-free halide perovskites become recognized as novel candidates for ferroelectrics and X-ray detection. However, molecular self-assembly of these perovskites and its influence remain unexplored. Here, we prepare large high-quality DABCO-NH4X3 (DABCO = N-N′-diazabicyclo[2.2.2]octonium, X = Cl, Br, I) single crystals and demonstrate the understandings of how halide-modulated molecular assembly affects their crystal packing, band nature, mechanical and electrical properties, and final optoelectronic performance. In this series, the 1D crystal packing and low carrier effective masses endow superior in-plane charge transport for the I-based crystal. As such, higher carrier mobility (110 versus ∼10–20 cm2 V−1 s−1) and longer charge diffusion length (∼90 versus ∼50 μm) are achieved in contrast to the Cl- and Br-based analogs. The excellent charge transport properties finally translate to highly efficient X-ray detection and imaging for the I-based crystal detector, with a sensitivity up to 567 μC Gyair−1 cm−2 and a well-defined “heart” X-ray image.
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•Large, high-quality, metal-free perovskite series, DABCO-NH4X3 SCs are grown•Influence of halide-modulated molecular assembly on physical properties is explored•DABCO-NH4I3 shows superior in-plane charge transport and X-ray detection sensitivity•The feasibility of X-ray imaging based on metal-free perovskites is demonstrated
Molecular self-assembly plays a critical role in crystal engineering for the design and fabrication of novel metal-free perovskite compounds. Here, we demonstrate the understandings of halide-modulated molecular assembly via hydrogen bonding in metal-free perovskites and its influence on their crystal packing, band nature, mechanical and electrical properties, and final optoelectronic performance. We found increasing halide radius leads to a gradual transition of band nature and narrower band gaps. The crystal with superior in-plane charge transport exhibits higher carrier mobility and better X-ray detection sensitivity. With a variety of nonmetallic and organic groups readily available for the A, B, and X sites, fine-tuned properties, and free of associated toxicity, this work benefits the understanding of molecular self-assembly behavior and is intended to inspire activities to study an assortment of novel ABX3 perovskite materials for potential biological applications.
Metal-free perovskite series, DABCO-NH4X3 (X = Cl, Br, I), exhibit a remarkable variety of perovskite-type structures. Large and high-quality versions of the three single crystals enable a detailed characterization of the halide-dependent multiple physical properties. In this series, DABCO-NH4I3 exhibits superior in-plane charge transport and the crystal device shows X-ray detection sensitivity of 567 μC Gyair−1 cm−2. Meanwhile, the feasibility of X-ray imaging is demonstrated with a well-defined “heart” image.