Semitransparent inverted polymer solar cells employing a sol-gel-derived TiO(2) electron-selective layer on FTO and MoO(3)/Ag/MoO(3) transparent electrode

We report a new semitransparent inverted polymer solar cell (PSC) with a structure of glass/FTO/nc-TiO(2)/P3HT:PCBM/MoO(3)/Ag/MoO(3). Because high-temperature annealing which decreased the conductivity of indium tin oxide (ITO) must be handled in the process of preparation of nanocrystalline titanium oxide (nc-TiO(2)), we replace glass/ITO with a glass/fluorine-doped tin oxide (FTO) substrate to improve the device performance. The experimental results show that the replacing FTO substrate enhances light transmittance between 400 and 600 nm and does not change sheet resistance after annealing treatment. The dependence of device performances on resistivity, light transmittance, and thickness of the MoO(3)/Ag/MoO(3) film was investigated. High power conversion efficiency (PCE) was achieved for FTO substrate inverted PSCs, which showed about 75% increase compared to our previously reported ITO substrate device at different thicknesses of the MoO(3)/Ag/MoO(3) transparent electrode films illuminated from the FTO side (bottom side) and about 150% increase illuminated from the MoO(3)/Ag/MoO(3) side (top side).