High performance polythiophene/fullerene bulk-heterojunction solar cell with a TiOx hole blocking layer

Insertion of a $\mathrm{Ti}{\mathrm{O}}_x$ layer between the Al electrode and the active layer of an organic photovoltaic cell resulted in a high performance with 94% durability under irradiation $(100\mathrm{mW}∕{\mathrm{cm}}^2)$ for $100\mathrm{h}$ and had improved fill factor and open circuit voltage. An efficiency of 4.05% was achieved by using the cell containing a $\mathrm{Ti}{\mathrm{O}}_x$ layer fabricated and measured in ambient atmosphere. The $\mathrm{Ti}{\mathrm{O}}_x$ layer works as an effective barrier to physical damage and chemical degradation, resulting in high durability under aerobic conditions, and also serves as a hole blocking layer, resulting in improved parallel resistance and rectification.