Although a considerable number of solvent based methodologies have been developed for exfoliating black phosphorus, so far there are no reports on controlled organization of these exfoliated nanosheets on substrates. Here, for the first time to the best of our knowledge, a mixture of N-Methyl-2-pyrrolidone (NMP) and deoxygenated water is employed as a subphase in Langmuir Blodgett (LB) trough for assembling the nanosheets followed by their deposition on substrates and studied its field effect transistor (FET) characteristics. Electron microscopy reveals the presence of densely aligned, crystalline, ultra-thin sheets of pristine phosphorene having lateral dimensions larger than hundred of microns. Furthermore, these assembled nanosheets retain their electronic properties and show a high current modulation of 10^4 at room temperature in FET devices. The proposed technique provides semiconducting phosphorene thin films that are amenable for large area applications.
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