| 초록 |
We demonstrate highly efficient inverted polymer solar cells (I-PSCs) using electrostatically self-assembled nonconjugated polyelectrolytes (NPEs) as an ideal interlayer. As cathode modifiers, the NPEs are solution-processed on indium tin oxide (ITO) cathode at the low annealing temperature of 80 oC. Using Kelvin Probe measurement and X-ray photoelectron spectroscopy, we confirm that the NPEs can dramatically reduce the work function of ITO from 4.8 eV to 4.0 eV due to interfacial dipoles originated from the existence of the protonated amines of the NPEs on the ITO surface. In I-PSC application, the ITO/NPE cathodes can provide a high built-in field for breaking electric symmetry and an ohmic contact with the lowest unoccupied molecular orbital level of fullerene acceptor. As a result, the I-PSCs exhibit UV-independent device operation with high power conversion efficiencies approaching 6.3%. |
