Figure 3
Spectral responsivity and external quantum efficiency of C60 nanorod photoconductor devices.
(a) Relative comparison of spectral responsivity obtained for C60 nanorod only and P3HT or CdSe NC photodoped C60 nanorod devices. Responsivity was measured using an applied electric field of 10 Vµm-1 and a modulation frequency of 235 Hz. All devices display photosensitivity across the full visible spectrum with the photodoping significantly enhancing the responsivity by up to 2 orders of magnitude. (b) Electric field dependent spectral responsivity of PbS NC photodoped device. The responsivity spectrum follows the C60 absorption spectrum in the visible region, confirming that the ultralow photodoping provided via PbS NCs enhances the photosensitivity of C60 nanorods. The spectral responsivity is extended by the use of PbS NC to provide UV-vis-NIR sensitivity. (c) The EQE of a P3HT photodoped device as a function of applied electric field and wavelength displaying a peak EQE approaching ~100% at 415 nm. (d) The EQE of a PbS NC photodoped device as a function of applied electric field and wavelength. It can be seen that EQE of the device is strongly field dependent in the region where the C60 nanorods absorb (350–750 nm) whilst in spectral range (750–1150 nm) the EQE remains below ~2%, even with increase in the applied electric field.
