Optical display film as flexible and light trapping substrate for organic photovoltaics

We demonstrate flexible small molecular solar cells on periodically patterned plastic substrate (LCD display film) using a highly transparent poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) electrode with flexible thin atomic layer deposited (ALD) AlO_x top and bottom encapsulation. The organic photovoltaic device (OPV) on this display film shows a power conversion efficiency of 7.48%, which is a 13.0% improvement as compared to a device fabricated on a planar poly-ethylen-terephtalate (PET) substrate (6.62%) and even higher than the efficiency of a device using planar glass substrate (7.15%). The improvement is mainly due to an enhanced harvesting of photons with wavelengths shorter than 500 nm. Moreover, the fully encapsulated device is sufficiently flexible to withstand a bending with a 10 mm radius for more than 50 cycles at ambient condition. These results indicate that the use of standard optical display films is a cheap, simple and efficient way to increase the photocurrent and overall efficiency of organic photovoltaic devices.