All-solution-processed organic solar cells with conventional architecture

All-solution processed organic solar cells with a conventional device structure were demonstrated. The evaporated low work function LiF/Al electrode was replaced by a printed high work function silver electrode combined with an additional electron transport layer (ETL). Two electron transport layers were tested: (I) zinc oxide (ZnO) nanoparticles and (II) poly[(9,9-bis(3'-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9–dioctylfluorene)] (PFN). Devices with printed silver nanoparticle inks on top of the ZnO electron transport layer lead to crack formation in the silver layer during the drying and sintering. The crack formation was avoided by using PFN as electron transport layer. The sputtered high work function ITO electrode was substituted by a printed composite electrode containing inkjet-printed silver grids in combination with high conductivity poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). All-solution processed solar cells demonstrated a power conversion efficiency of 1.94%.