Low Work Function Lacunary Polyoxometalates as Electron Transport Interlayers for Inverted Polymer Solar Cells of Improved Efficiency and Stability

• DOI: 10.1021/acsami.7b04600
• Publication Date: 2017-06-06T15:30:36Z
• Authors: Marinos Tountas; Yasemin Topal; Ermioni Polydorou; Anastasia Soultati; Apostolis Verykios; Andreas Kaltzoglou; Theodoros A. Papa...; Florian Auras; Kostas Seintis; Mihalis Fakis; Leonidas C. Palilis; Dimitris Tsikritzis; Stella Kennou; Matroni Koutsoureli; George Papaioannou; Mustafa Ersöz; Mahmut Kus; Polycarpos Falaras; Dimitris Davazoglou; Panagiotis Argitis; Maria Vasilopoulou
• Keywords: Charge carrier; Quantum Efficiency

Effective interface engineering has been shown to play a vital role in facilitating efficient charge-carrier transport, thus boosting the performance of organic photovoltaic devices. Herein, we employ water-soluble lacunary polyoxometalates (POMs) as multifunctional interlayers between titanium dioxide (TiO2) electron extraction/transport layer and photoactive film simultaneously enhance efficiency, lifetime, photostability polymer solar cells (PSCs). A significant reduction work function (WF) TiO2 upon POM utilization was observed, with magnitude being controlled by negative charge anion selection addenda atom (W or Mo). By inserting interlayer ∼10 nm thickness into device structure, improvement power conversion efficiency obtained; optimized POM-modified poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2- 33 ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]:[6,6]-phenyl-C70 butyric acid methyl ester (PTB7:PC70BM)-based PSCs exhibited an 8.07%, which represents 21% enhancement compared reference cell. Similar results were obtained devices based on poly(3-hexylthiophene) (P3HT) acceptors different energy levels, such PC70BM indene-C60 bisadduct (IC60BA), enhanced their up 4.34 6.21%, respectively, when using interlayers; this 25-33% cells. Moreover, increased lifetime under ambient air improved constant illumination observed Detailed analysis shows that improvements stability synergistically stem from reduced coverage, nanomorphology blend, interfacial recombination losses, superior transfer, more effective exciton dissociation at layer/POM/TiO2 interfaces.