ITO-Free Semitransparent Organic Solar Cells Based on Silver Thin Film Electrodes

Abstract

ITO-free semitransparent organic solar cells (OSCs) based on MoO3/Ag anodes with poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester films as the active layer are investigated in this work. To obtain the optimal transparent (MoO3)/Ag anode, ITO-free reference OSCs are firstly fabricated. The power conversion efficiency (PCE) of 2.71% is obtained for OSCs based on the optimal MoO3(2 nm)/Ag (9 nm) anode, comparable to that of ITO-based reference OSCs (PCE of 2.85%). Then based on MoO3(2 nm)/Ag (9 nm) anode, ITO-free semitransparent OSCs with different thickness combination of Ca and Ag as the cathodes are investigated. It is observed from our results that OSCs with Ca (15 nm)/Ag (15 nm) cathode have the optimal transparency. Meanwhile, the PCE of 1.79% and 0.67% is obtained for illumination from the anode and cathode side, respectively, comparable to that of similar ITO-based semitransparent OSCs (PCE of 1.59% and 0.75% for illumination from the anode and cathode side, resp.) (Sol. Energy Mater. Sol. Cells, 95, pp. 877–880, 2011). The transparency and PCE of ITO-free semitransparent OSCs can be further improved by introducing a light couple layer. The developed method is compatible with various substrates, which is instructive for further research of ITO-free semitransparent OSCs.

Flexible ITO-Free Organic Solar Cells Based on <named-content content-type="math" xlink:type="simple"> <inline-formula> <tex-math notation="TeX">$\hbox{MoO}_{3}/\hbox{Ag}$</tex-math></inline-formula></named-content> Anodes

“…In our previous work [26], [27], ðMoO 3 Þ=Ag electrodes have been investigated in the view of how to reduce the metal percolation threshold. After the study of the electrical, optical and morphological properties of ðMoO 3 Þ=Ag electrodes deposited onto glass substrates, the optimal MoO 3 (2 nm)/Ag (9 nm) electrode is obtained due to its good properties in optical transparency and electrical conductivity.…”

Efficient Inverted ITO-Free Organic Solar Cells Based on Transparent Silver Electrode with Aqueous Solution-Processed ZnO Interlayer

“…Secondly, the dried glass substrates were transferred into an ultrahigh vacuum chamber with a pressure below 5 × 10 −4 Pa. To obtain the MoO 3 /Ag electrodes, MoO 3 and Ag films were thermally evaporated on glass substrates sequentially with the evaporation rate of 0.02 nm/s and 0.1 nm/s, and the details of electrode deposition can be found in our previous works [32][33][34]. The thickness of 2 nm given here has to be a nominal value obtained by the quartz crystal monitor calibrated with a step profiler, representing the amount of MoO 3 on the sample.…”

“…It has been reported in our previous works that the introduction of 2 nm thick unclosed MoO 3 layer may create preferred nucleation sites on the substrate to enhance the lateral growth of Ag film, which improves the electrical, optical, and morphological properties of MoO 3 /Ag electrodes [32][33][34]. Based on the optimal MoO 3 (2 nm)/Ag (9 nm) anode with high transparency and good conductivity, ITOfree OSCs with a conventional structure are fabricated on glass substrates, and the resulted device shows the comparable performance compared to the ITO-based reference OSCs [32,33].…”

“…However, the conventional OSCs in above works show the fast performance degradation and the relatively poor stability even stored in the N 2 -filled glove box [33]. Fortunately, compared to conventional OSCs, the stability could be obviously improved by employing an inverted structure and more stable high work function metal anodes [35,36].…”

“…Based on the optimal MoO 3 (2 nm)/Ag (9 nm) anode with high transparency and good conductivity, ITOfree OSCs with a conventional structure are fabricated on glass substrates, and the resulted device shows the comparable performance compared to the ITO-based reference OSCs [32,33]. Furthermore, flexible ITO-free OSCs fabricated on poly(ethylene terephthalate) (PET) substrates exhibit a good performance and excellent mechanical flexibility [34], which reveals the potential of Ag electrode for the roll-to-roll mass fabrication of OSCs.…”