All-solution-processed inverted polymer solar cells with low temperature, water-processable hybrid electron-collecting layers

Abstract

We herein report on a highly simple and efficient all-solution-processed inverted polymer solar cell (PSC), which consists of a bulk-heterojunction (BHJ) photovoltaic (PV) layer with a low-temperature, water-processable electron-collecting layer (ECL) made of a hybrid poly(ethylene oxide) (PEO) and cesium carbonate (Cs₂CO₃) compound. For the BHJ PV layer of poly(3-hexylthiophene):phenyl C₆₁-butyric acid methyl ester (P3HT:PCBM) with the hybrid PEO:Cs₂CO₃ ECL and a solution-coated anode of silver nanoparticles (NPs), it was found that a power conversion efficiency (PCE) of around 2.5% could be achieved for PSCs fabricated entirely from solution in air at a low processing temperature below 150 °C, using the inverted structure on a glass substrate. This excellent PV performance may be attributed to efficient photo-generated charge-carrier collection, due to the suitable work function of the hybrid PEO:Cs₂CO₃ ECL used. Moreover, even for a fully solution-processed flexible inverted PSC on a plastic substrate, a relatively high PCE of 1.3% was obtained. The use of this hybrid ECL in all-solution-processable inverted PSCs could be of considerable benefit in the development of cost-effective and highly efficient all-solution- and roll-to-roll processed inverted PSCs.