Facile preparation of TiOX film as an interface material for efficient inverted polymer solar cells

Titanium oxide (TiOX) is an effective electron transport layer in polymer solar cells (PSCs). Here, we report an efficient inverted polymer solar cell based on P3HT and fullerenes using a high density, single-step solution processed amorphous TiOX (alpha-TiOX) film as an electron transport layer. The alpha-TiOX film was prepared by spin coating tetrabutyl titanate (TBT) isopropanol solution onto ITO coated glass in a glovebox filled with N-2 and then annealing at different temperatures in air. The films with high light transmittance are very smooth. The PSCs with the alpha-TiOX electron transport layer showed enhanced photovoltaic performance in comparison with the device using PEDOT:PSS as the anode buffer layer. The optimized power conversion efficiency (PCE) of the PSCs based on P3HT/PC61BM and P3HT/PC71BM with the alpha-TiOX electron transport layer reached 4.25% and 4.65%, respectively, under AM1.5G illumination (100 mW cm(-2)). In addition, the PSCs with the alpha-TiOX electron transport layer exhibited good stability. The results indicate that facile preparation of alpha-TiOX films using cheap TBT is promising for high-efficiency PSCs and large-scale fabrication of flexible electronics.