High-Efficiency Oxide Heterojunction Solar Cells Using Cu2O Sheets

An inexpensive oxide heterojunction solar cell, consisting of a transparent conducting ZnO thin film deposited on a Cu2O sheet prepared by oxidizing copper at a high temperature, has been demonstrated. High-energy conversion efficiencies over 1% were obtained in Al-doped ZnO (AZO)/Cu2O devices fabricated using AZO thin films prepared by pulsed laser deposition (PLD) or r.f. magnetron sputtering. An open-circuit voltage of 0.41 V, a short-circuit current density of 7.13 mA/cm2, a fill factor of 0.42 and an energy conversion efficiency of 1.21% were obtained in a PLD-AZO/Cu2O device under AM2 solar illumination. The high efficiency of AZO/Cu2O devices is attributed to Cu2O sheets with excellent crystallinity and the low damage resulting from AZO depositions at low temperature.