Inverted polymer solar cells comprising a solution-processed work-function tunable hybrid electron-collecting layer

In this work, a solution-processed, work-function tunable, and low-temperature processed hybrid electron-collecting layer comprising poly(ethylene oxide) (PEO) and cesium acetate is introduced for inverted polymer solar cells. The ratio of the PEO to CH3COOCs is optimized in terms of the measurements of work function and current-voltage characteristics. The hybrid interlayer lowers the work function of ITO from 4.82 eV to 4.21 eV measured by the Kelvin probe. Inverted polymer solar cell based on blends of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) with PEO: CH3COOCs interlayer exhibits enhanced power conversion efficiency of 2.82% under 100 mW/cm(2) AM1.5 illuminations. The improvement in performance is mainly ascribed to interfacial tuning between the ITO electrode and the active layer as well as improving adhesion, compatibility and wettability, resulting in improved charge transport and reduced contact resistance. Furthermore, since the process temperature can be kept below 110 degrees C during the fabrication process, this method of utilizing of solution processable PEO: CH3COOCs hybrid interlayer is very attractive to the large area roll-to-roll fabrication of cost-effective polymer solar cells due to its simplicity. (C) 2014 AIP Publishing LLC.