Ultralong compositional tunable InGaN nanowires as a photoanode, grown by chemical vapour deposition technique using catalyst-free approach, exhibits high efficiency solar water splitting for the first time without co-catalyst. The high density of unique ultralong InGaN nanowires with high intense multiband emission in the visible region improves the absorption of photon, thereby significantly increasing the photocurrent density of similar to 32 mA/cm(2) at 1.0 V against Pt counter electrode. The small diameter of InGaN nanowires favours the diffusion of the charge carriers to the surface before recombination which results in enhanced solar energy conversion efficiency. Multiband InGaN nanowires demonstrate a maximum applied bias photon-to-current efficiency of similar to 16.19% at 0.34 V under AM1.5G one sun illumination. (C) 2016 Elsevier B.V. All rights reserved.