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The bottom‐up preparation of two‐dimensional material micro‐nano structures at scale facilitates the realisation of integrated applications in optoelectronic devices. Fibrous Phosphorus (FP), an allotrope of black phosphorus (BP), is one of the most promising candidate materials in the field of optoelectronics with its unique crystal structure and properties.[1] However, to date, there are no bottom‐up micro‐nano structure preparation methods for crystalline phosphorus allotropes.[1c, 2] Herein, we present the bottom‐up preparation of fibrous phosphorus micropillar (FP‐MP) arrays via a low‐pressure gas‐phase transport (LP‐CVT) method that controls the directional phase transition from amorphous red phosphorus (ARP) to FP. In addition, self‐powered photodetectors (PD) of FP‐MP arrays with pyro‐phototronic effects achieved detection beyond the band gap limit. Our results provide a new approach for bottom‐up preparation of other crystalline allotropes of phosphorus. [ABSTRACT FROM AUTHOR]

Black phosphorus (BP) is an emerging two-dimensional semiconductor material, which has interesting structural features and broad application prospects in the fields of optoelectronic devices, energy storage, and biomedicine. However, a large amount of evidence is still needed to clarify the potential mechanism for the synthesis of high-quality BP crystals in chemical vapor transport (CVT) reactions. In this work, high-purity BP crystals were synthesized by the CVT method in an amorphous red phosphorus (aRP), Sn and I2 system. We found that the synthesis of BP experienced the three stage structural transformation of aRP–P4-Hittorf's phosphorus (HP)–BP. First, the phase transition of aRP and P4 molecules was reversible in the sublimation stage; then, the P4 molecules were gradually transformed into the HP structure in the transportation and deposition stage; however, the nucleation of BP quickly inhibited the growth of HP and completed the phase transition quickly; finally, the remaining P4 molecules were transformed into the BP structure, which promoted the growth of BP crystals. Crystallization kinetics explained the nucleation mechanism during the formation of BP, and the competitive nucleation between HP and BP provided the possibility for the bottom-up preparation of BP nanobelts. [ABSTRACT FROM AUTHOR]