Efficient Flexible White-Light Photodetectors Based on BiFeO₃ Nanoparticles

A heterostructured white-light photodetector was fabricated by the sequential deposition of zinc oxide (ZnO), bismuth ferrite (BFO), and poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate (PEDOT:PSS) onto a flexible poly(ethylene terephthalate) (PET) substrate. Central to this unique structure is an n + –n junction at the ZnO–BFO interface, which allows the device to drive unusually large currents. The intrinsic BFO electric field, arising from the depletion region within the ferroelectric material, is reduced through the combined effect of two barrier fields formed at the BFO–Au and ZnO–BFO interfaces. The combination of these three fields reduces parasitic recombination and causes photoexcited electron–hole pairs to drift to the electrodes. The photocurrent sensitivity and photocurrent gain were determined to be 0.04 A/W and 105, respectively. The decay time extracted from the photoresponse curve was 6 s, whereby the photocurrent drops by a factor of 30. In addition, the device exhibits good flexibility and retains almost constant performance after 100 bending cycles through a 90° angle.