Efficient polymer solar cells with a solution-processed and thermal annealing-free RuO2 anode buffer layer

A new method is developed to prepare RuO2 films through UVO treatment of solution-processed ruthenium(III) acetylacetonate (Ru(acac)(3)) without thermal annealing. By introducing RuO2 as an anode buffer layer, highly efficient polymer solar cells (PSCs) have been achieved. The resultant RuO2 layer exhibits high light transmittance in the visible range. Remarkable improvements in the short-circuit current density (J(sc)) of the PSCs can be achieved upon the introduction of the RuO2 buffer layer. The PSCs with the RuO2 anode buffer layer demonstrate improved photovoltaic performance in comparison with the devices using poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) as the anode buffer layer. The power conversion efficiency (PCE) of the PSCs based on P3HT: PCBM and P3HT: ICBA reaches as high as 4.19% and 7.07%, respectively. An even higher PCE of 7.45% is realized by adopting a new conjugated polymer, PBDTBDD, as the donor. The results demonstrate that RuO2 has great potential as a hole collection material for highly efficient PSCs.