Tunable Organic PV Parallel Tandem with Ionic Gating



A novel type of tunable organic photovoltaic (OPV) tandem device with ionic gating by in-situ ionic liquid is presented. This device is comprised of two solution-processed polymeric OPV cells connected in parallel by a dry-laminated transparent multiwall carbon nanotube (MWCNT) interlayer. The interlayer MWCNT of this 3-terminal tandem device plays a role of a common electrode with a Fermi level that can be tuned via ionic gating to turn it into a common cathode, collecting photo-generated electrons from both sub-cells. Ionic gating employs electric double layer charging of the MWCNT in order to lower the work function of the common CNT electrode and increase its n-type conductivity. This tandem device is fabricated in ambient conditions via dry-lamination of MWCNT transparent sheets The new results demonstrating the different regimes of ionic gating at low, medium, and high gating voltages V_{gate} are presented, showing the optimal doping of the MWCNT, then favorable doping of acceptor PCBM ([6,6]-phenyl-C₆₁-butyric acid methyl ester), followed by the deterioration of performance at V_{gate} over the threshold voltage when doping of polymeric layers of sub-cell OPVs starts taking place. The doping of PCBM and polymers is additionally confirmed by the change in the charging and discharging current dynamics at high V_{gate} above the threshold.


Includes supplementary material


Solar-cells, Carbon nanotubes, Photovoltaic cells--Materials, Ionic solutions, Electrodes, Butyric acid


"Support for this work was provided from the Ministry of Education and Science of the Russian Federation in the framework of Increase Competitiveness Program of NUST “MISiS” (No. K2- 2015-014). Partial financial support by Welch Foundation Grant No. AT-1617 is also appreciated."


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