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 cm 2 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.