**4. Conclusions**

In conclusion, we have reported a modified, environmentally friendly polyol method to synthesize AgNRs with higher yield using a cosolvent consisting of glycerol and DI water, with other factors determined by employing the Taguchi design. Structural characterization revealed that AgNRs grew along the track of rings from the early stage of the reaction. To achieve high yield of AgNRs, the addition of DI water or EG was significant, which acted as the medium to increase ion mobility and another reductant that is less reductive to control the growth direction. Otherwise, the ratio of it should be precisely controlled. As a result, AgNRs with ring diameter ranging from 7.17 to 42.94 μm and wire diameter of about 76 nm were synthesized with higher yield. The research indicates the potential to synthesize pure AgNRs and to further apply them in flexible WBG semiconductor devices.

**Author Contributions:** Conceptualization, Z.L. and H.N.; methodology, R.Y. and D.G.; validation, Z.L., X.F., and J.C.; resources, J.P. and R.Y.; data curation, P.X., Y.W., and X.Z.; writing—original draft preparation, Z.L. and D.G.; writing—review and editing, J.P. and H.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by Key Area Research and Development Program of Guangdong Province (No.2019B010934001), National Natural Science Foundation of China (Grant No.51771074, 61804029 and 61574061), Major Integrated Projects of National Natural Science Foundation of China (Grant No.U1601651), Basic and Applied Basic Research Major Program of Guangdong Province (No.2019B030302007), the Guangdong Natural Science Foundation (No.2018A030310353), Science and Technology Project of Guangzhou (No.201904010344), Fundamental Research Funds for the Central Universities (No.2019MS012), Open Project of Guangdong Province Key Lab of Display Material and Technology (No.2017B030314031), and Open Fund of Foshan University.

**Conflicts of Interest:** The authors declare no conflict of interest.
