Probing Ternary Solvent Effect in High Voc Polymer Solar Cells Using Advanced AFM Techniques
2016
Li, Chao | Ding, Yi | Soliman, Mikhael | Lorenzo, Josie | Dhasmana, Nitesh | Chantharasupawong, Panit | Ievlev, Anton V. | Gesquiere, Andre J. | Tetard, Laurene | Thomas, Jayan
This work describes a simple method to develop a high Vₒc low band gap PSCs. In addition, two new atomic force microscopy (AFM)-based nanoscale characterization techniques to study the surface morphology and physical properties of the structured active layer are introduced. With the help of ternary solvent processing of the active layer and C₆₀ buffer layer, a bulk heterojunction PSC with Vₒc more than 0.9 V and conversion efficiency 7.5% is developed. In order to understand the fundamental properties of the materials ruling the performance of the PSCs tested, AFM-based nanoscale characterization techniques including Pulsed-Force-Mode AFM (PFM-AFM) and Mode-Synthesizing AFM (MSAFM) are introduced. Interestingly, MSAFM exhibits high sensitivity for direct visualization of the donor–acceptor phases in the active layer of the PSCs. Finally, conductive-AFM (cAFM) studies reveal local variations in conductivity in the donor and acceptor phases as well as a significant increase in photocurrent in the PTB7:ICBA sample obtained with the ternary solvent processing.
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