# Effects of Co-Solvents on the Performance of PEDOT:PSS Films and Hybrid Photovoltaic Devices
## 5 Conclusions  
Spin coating was demonstrated for the deposition of PEDOT:PSS films with co-solvents on textured silicon substrates. An accumulation of the PEDOT:PSS in the valleys of the texturing was observed. Co-solvents decreased the sheet resistance of the films, both DMSO and EG having  
Figure 6: Reproducibility of device performance for different PEDOT:PSS recipes.  
comparable effects. The reflectance of the devices under test confirmed the anti-reflective properties of PEDOT:PSS films as well as the irregularity of the PEDOT:PSS films. The reflectivity measurements further suggest that EG as a co-solvent is more prone to accumulation and irregular films. The contact resistance of the Ag/PEDOT:PSS interface for this device design was characterized by finding a much lower value than originally assumed. Finally, photovoltaic devices were fabricated with the PEDOT:PSS recipes and characterized and a significant improvement in device performance was found. This improvement can be attributed to the anti-reflective properties of the PEDOT:PSS films, the reduced series resistance induced by the co-solvents, and the optimization of the front metal contact design. EG (7%) appeared to have a better reproducibility and fundamental performance. Our champion cell with 11.3% efficiency ranks amongst the top performing front junction PEDOT:PSS solar cells [17]. For comparison, the best performing front junction PEDOT:PSS cell has achieved an efficiency of 14.6% [18]. Future work will be aimed at understanding surface morphology variation of PEDOT:PSS due to co-solvents and device optimization by reducing the series and shunt resistance losses.  
Conceptualization, J.H. and A.I.; validation, J.H., A.I., D.A.A.T. and B.T.; writing--original draft preparation, J.H. and A.I.; writing--review and editing, D.A.A.T. and R.O.; supervision, J.Z. and R.O.; project administration, R.O.; funding acquisition, R.O.  
This material is based upon work primarily supported by the Engineering Research Center Program of the National Science Foundation and the Office of Energy Efficiency and Renewable Energy of the Department of Energy under NSF Cooperative Agreement No. EEC-1041895. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation or Department of Energy.  
Work at the ASU Solar Power Lab by [PERSON], [PERSON] and [PERSON] was supported by the Nanotechnology collaborative Infrastructure Southwest (NCI-SW) with funding from NSF- ECCS1542160. J-V, quantum efficiency and electroluminescence measurements were measured at the Institute of Energy Conversion (IEC) under the guidance of [PERSON], [PERSON] and [PERSON]. UV-VIS reflectance measurements were also conducted at IEC under supervision of [PERSON]. Electron beam deposition was done at UD Nanofabrication facility under guidance of [PERSON]. Hall effect measurements for conductivity measurements were performed by [PERSON]. XPS survey data was performed by [PERSON] at the University of Delaware. SEM characterization was done by [PERSON] and [PERSON].  
The authors declare no conflict 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.