Tountas, MarinosTopal, YaseminPolydorou, ErmioniSoultati, AnastasiaVerykios, ApostolisKaltzoglou, AndreasPapadopoulos, Theodoros A.2020-03-262020-03-2620171944-8244https://dx.doi.org/10.1021/acsami.7b04600https://hdl.handle.net/20.500.12395/35265Effective 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 the titanium dioxide (TiO2) electron extraction/transport layer and the organic photoactive film to simultaneously enhance the efficiency, lifetime, and photo stability of polymer solar cells (PSCs). A significant reduction in the work function (WF) of TiO2 upon POM utilization was observed, with the magnitude being controlled by the negative charge of the anion and the selection of the addenda atom (W or Mo). By inserting a POM interlayer with similar to 40 nm thickness into the device structure, a significant improvement in the power conversion efficiency was obtained; the 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) carb onyl] thieno [3,4-b] thiophenediylp [6,6]-phenyl-C-70 butyric acid methyl ester (PTB7:PC70BM)-based PSCs exhibited an efficiency of 8.07%, which represents a 21% efficiency enhancement compared to the reference TiO2 cell. Similar results were obtained in POM-modified devices based on poly(3-hexylthiophene) (P3HT) with electron acceptors of different energy levels, such as PC70BM or indene-C-60 bisadduct (IC(60)BA), which enhanced their efficiency up to 4.34 and 6.21%, respectively, when using POM interlayers; this represents a 25-33% improvement as compared to the reference cells. Moreover, increased lifetime under ambient air and improved photostability under constant illumination were observed in POM-modified devices. Detailed analysis shows that the improvements in efficiency and stability synergistically stem from the reduced work function of TiO2 upon POM coverage, the improved nanomorphology of the photoactive blend, the reduced interfacial recombination losses, the superior electron transfer, and the more effective exciton dissociation at the photoactive layer/POM/TiO2 interfaces.en10.1021/acsami.7b04600info:eu-repo/semantics/openAccesspolymer solar cellslacunarypolyoxometalatestitanium oxidestabilitylow work functionArticle927227732278728585803Q1WOS:000405764700073Q1