This paper reports heterojunction solar cells consisting of InP nanopillars and aluminum-doped zinc oxide (AZO). The AZO layer sputtered on an InP surface is used not only as a transparent electrode, but also as an excellent rectifying junction with InP. More importantly, the wide-bandgap-AZO functions as a window layer of solar cells, thereby suppressing carrier recombination loss at the AZO-InP hetero-interface. The InP nanopillar array reduces the light reflectance and increases the optical path length of the solar cells. The AZO-InP nanopillar-based heterojunction solar cells exhibited an open-circuit voltage, short-circuit current density, fill-factor, and power-conversion efficiency of 0.68 V, 36.8 mA/cm(2), 68%, and 17.1%, respectively, under air-mass 1.5 simulated solar illumination (100 mW/cm(2)). (C) 2016 Elsevier B.V. All rights reserved.