Tattoo-Like Transferable Hole Selective Electrodes for Highly Efficient, Solution-Processed Organic Indoor Photovoltaics

In solution-processed organic photovoltaics the deposition of charge selective interlayers or electrodes on top of the photoactive layer is a well-known critical step, typically involving either surface treatments or addition of surfactants. As a general strategy to overcome such processing issues, here a simple and scalable tattoo-based technique is presented for the direct transfer of selective poly(3,4-ethylenedioxythiophene)/polystyrene-sulfonate (PEDOT:PSS) contacts, previously screen printed on commercial temporary tattoo paper, on top of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) films. The obtained structure works both in sunlight and in artificial low-light indoor conditions. In the latter case, which represents a very interesting application scenario for cost-effective flexible and lightweight photovoltaic chargers, excellent photo-conversion performances, in excess of 7.0 %, are achieved, the best performance reported so far for artificial light conversion with OPV based on the well-known P3HT and PCBM blend. As a proof-of-concept toward real applications, this electrode transfer strategy is adopted to fabricate a 6 cm² mini-module that in indoor low-light conditions can power a temperature-humidity sensor endowed with an LCD display. These results show that tattoo-like transfer of charge selective electrodes is a promising strategy to simplify the fabrication process flow of organic photovoltaics tailored for low light conditions.