Thin-film ZnO/Cu2O solar cells incorporating an organic buffer layer

This work presents a novel approach to overcoming the limitations of low long-wavelength absorption and short charge transport lengths in electrodeposited bilayer ZnO/Cu2O solar cells. Here we reduce the Cu2O thickness to approximately the minority carrier transport length and coat a film of a semiconducting polymer between the Cu2O and a top electrode. We demonstrate efficient hole-injection from Cu2O into the semiconducting polymer as well as blocking of electrons by the polymer. We also show optical confinement of long-wavelength light inside of the collection area in the Cu2O resulting from refractive index mismatch between the polymer and Cu2O. This leads to improved extraction of charge carriers and higher Jsc values from much thinner Cu2O layers than are normally used.

► Optical confinement is used to enhance the photocurrent collection in elecrodeposited ZnO/Cu2O devices.
► The thickness of the Cu2O layer is reduced to approximately the minority carrier transport length and thin PFB layers reflect light back into the collection zone of the device.
► The PFB films also act as charge- and shunt-blocking layers.
► We report exceptionally high Jsc values from devices containing thin (0.85 μm) Cu2O layers.
► There is efficient charge transfer across the Cu2O/PFB interface.