Nitrogen‐Doped Carbon Nano‐Onions Decorated on Graphene Network: A Novel All‐Carbon Composite Counter Electrode for Dye‐Sensitized Solar Cell with a 10.28% Power Conversion Efficiency

A desirable counter electrode material for dye‐sensitized solar cells (DSSCs) needs to have superior electrocatalytic activity, low charge‐transfer resistance, and long‐term stability. Herein, the development of a composite of nitrogen‐doped carbon nano‐onions with modified reduced graphene (N‐CNOs/mGr) to achieve these merits is reported. The mGr network has high electrical conductivity to improve charge transfer; the N‐CNOs with pyridinic and graphitic N provide more electrocatalytic active sites for the reduction of I 3 − to I − , and the carbon composite demonstrates excellent electrochemical stability. The constructed DSSC with the N‐CNOs/mGr electrode presents better long‐term stability and a higher power conversion efficiency of 10.28% than those devices with conventional Pt (6.54%) and mGr (5.11%) electrodes. Therefore, the all carbon‐based composite will open up new opportunities for a variety of electrochemical device applications.