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, that typically involves either treatments of low surface energy films or the addition of surfactants into high surface tension formulations to improve the wettability. As a general strategy to overcome such processing issues, this thesis presents a simple and scalable tattoo-based transfer technique for the deposition of selective contacts on top of organic photo-active layers. In particular, is shown the possibility to pattern poly(3,4-ethylenedioxythiophene)/ polystyrene-sulfonate (PEDOT:PSS) by screen-printing on commercial temporary tattoo paper and to physically transfer these hole selective electrodes on top of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) films to complete a photovoltaic cell with inverted geometry. The obtained structure is demonstrated to work both in sunlight and in artificial low-light indoor conditions. In the latter case, which represents a very interesting application scenario for cost-effective and flexible photovoltaic chargers, excellent photo-conversion performances, in excess of 7.0 %, are achieved, the best performance reported so far for artificial light conversion with organic photovoltaics based on the well-known P3HT and PCBM blend. 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. Such a cost-effective technology can provide competitive performances for indoor energy harvesting with well-known model materials.
La deposizione di contatti selettivi è nota per essere un passaggio particolarmente critico nella produzione di celle fotovoltaiche organiche solution-processed. Le soluzioni comunemente adottate comprendono infatti invasivi trattamenti delle superfici per migliorarne la bagnabilità o complesse riformulazione degli inchiostri da depositare. Questo lavoro presenta come promettente alternativa un innovativo metodo di trasferimento di film conduttivi, reso possibile grazie all'impiego della comune carta trasferibile per tatuaggi. Tali film conduttivi, ottenuti depositando su carta tattoo del poly(3,4-ethylenedioxythiophene)/polystyrene-sulfonate (PEDOT:PSS), sono utilizzati in questo lavoro come elettrodi superiori in dispositivi fotovoltaici basati sui materiali poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). Tale processo, semplice da eseguire anche a mano, permette di trasferire elettrodi ottenuti su carta tattoo direttamente sulla superficie del materiale foto-attivo, senza coinvolgere pre-trattamenti delle superfici né complicati controlli di temperatura e pressione tipicamente associati alle tecniche di trasferimento. I dispositivi così ottenuti sono dimostrati funzionare efficientemente sia in condizioni di bassa illuminazione artificiale che in condizioni di radiazione solare. Nel primo caso, condizione di particolare interesse per il settore dell'energy-harvesting per l'Internet of Things, i dispositivi mostrano eccellenti efficienze di foto-conversione (PCE > 7 %), le più alte ad oggi riportate in condizioni di bassa illuminazione per dispositivi ottenuti con i noti materiali P3HT:PCBM. I risultati ottenuti su piccola scala dimostrano come il trasferimento tattoo rappresenti una valida alternativa per semplificare il processo produttivo di dispositivi fotovoltaici organici, trattandosi nel complesso di una tecnica compatibile con metodi di fabbricazione ad alta produttività.
Tattoo-like transferable hole selective electrodes for organic photovoltaics
PIVA, NICOLA
2017/2018
Abstract
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, that typically involves either treatments of low surface energy films or the addition of surfactants into high surface tension formulations to improve the wettability. As a general strategy to overcome such processing issues, this thesis presents a simple and scalable tattoo-based transfer technique for the deposition of selective contacts on top of organic photo-active layers. In particular, is shown the possibility to pattern poly(3,4-ethylenedioxythiophene)/ polystyrene-sulfonate (PEDOT:PSS) by screen-printing on commercial temporary tattoo paper and to physically transfer these hole selective electrodes on top of poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) films to complete a photovoltaic cell with inverted geometry. The obtained structure is demonstrated to work both in sunlight and in artificial low-light indoor conditions. In the latter case, which represents a very interesting application scenario for cost-effective and flexible photovoltaic chargers, excellent photo-conversion performances, in excess of 7.0 %, are achieved, the best performance reported so far for artificial light conversion with organic photovoltaics based on the well-known P3HT and PCBM blend. 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. Such a cost-effective technology can provide competitive performances for indoor energy harvesting with well-known model materials.| File | Dimensione | Formato | |
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2018_04_Piva.pdf
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https://hdl.handle.net/10589/139093