## 4 Conclusions  
In conclusion, we successfully integrated superconductors and organic materials in a vertically stacked structure by adding a protective Al layer prior to the harsher deposition of the top NbN electrode. We demonstrated that transport properties of the SC-O-SC devices consisting of Nb/MEH-PPV/Al/NbN are not due to pinholes: (i) EDS measurements depicted a significant metal-free organic layer; (ii) the junctions show typical space-charge-limited IV characteristics of single-layer organic semiconductor structures; (iii) the junction resistance increases as the temperature is lowered, down to temperatures just above the NbN TC; and (iv) a similar junction with an additional V\({}_{2}\)O\({}_{5}\) blocking layer had light-emitting properties down to the lowest temperatures.  
At temperatures below the TC of NbN, the onset of proximity induced superconductivity in the MEH-PPV layer is manifest. The zero-bias resistance across the junction reduces significantly with temperature following the superconducting transitions of both the Nb and NbN electrodes. Our measurements were performed at temperatures higher than 2 K. Given these results, it is reasonable to estimate that a complete Josephson current could be realized at lower temperatures or by reducing the voltage noise of the low current measurements.  
The stacked architecture we developed can serve as a platform for the fabrication and investigation of SC-OLEDs. Our measurements show proximity induced coherence in p-type MEH-PPV layers and suggests that these effects should be observable in other organic semiconductor thin films, at low but accessible temperatures. In addition, we successfully created a semi-transparent and superconducting top electrode. Thus, we have presented a flexible framework with which to study and observe the role of superconductor-induced coherence on the excitonic properties of organic light-emitting materials. Such coherence effects could have a pronounced impact on exciton formation and recombination and ultimately lead to brighter or even laser-like coherent emission upon electrical excitation, an elusive goal sought from many directions for organic semiconductors [31,32].  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app15010085/s1](https://www.mdpi.com/article/10.3390/app15010085/s1)]([https://www.mdpi.com/article/10.3390/app15010085/s1](https://www.mdpi.com/article/10.3390/app15010085/s1)), Figure S1: Electroluminescence at low temperature.  
Conceptualization, Y.R.T. and A.S.; Methodology, A.K., Y.R.T. and A.S.; Formal analysis, A.K., H.A., Y.R.T. and A.S.; Investigation, A.K. and H.A.; Resources, Y.R.T. and A.S.; Data curation, A.K. and Y.R.T.; Writing--original draft, A.K., Y.R.T. and A.S.; Writing--review & editing, Y.R.T. and A.S.; Supervision, Y.R.T. and A.S.; Project administration, H.A.; Funding acquisition, Y.R.T. and A.S. All authors have read and agreed to the published version of the manuscript.  
This research was partially funded by MOST-SFF #6068.  
Not applicable.  
The raw data that support the findings of this study are available from the corresponding authors upon reasonable request.  
The authors would like to thank [PERSON] and [PERSON] for their help with FIB and TEM, [PERSON] for assistance with the electrical wiring of the cryostat, and [PERSON] for assistance with profilometry. The authors are grateful to [PERSON] for providing the first batch of MEH-PPV.  
**Conflicts of Interest:** The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.