Enhanced efficiency and stability of polymer solar cells with TiO2 nanoparticles buffer layer

Abstract TiO 2 sols synthesized with a facile solution-based method were used as a buffer layer between the active layer and the cathode Al in conventional structure polymer solar cells (PSCs). Using transmission electron microscopy (TEM), selected area electron diffraction (SAED), X-ray diffraction (XRD) and atomic force microscopy (AFM), the morphological and crystallographic properties of synthesized TiO 2 nanoparticles (TiO 2 NPs) as well as the buffer layer were studied in detail. It was observed that by increasing H 2 O in the process of peptization both the crystallinity and particle size of TiO 2 NPs were enhanced, while the particles in sol showed a narrower size distribution conformed by dynamic light scattering. Inserting TiO 2 NPs as a buffer layer in conventional structure PSCs, both the power conversion efficiency ( PCE ) and stability were improved dramatically. PSCs based on the structure of ITO/PEDOT:PSS/P3HT:PCBM/TiO 2 NPs/Al showed the short-circuit current ( J sc ) of 12.83 mA/cm 2 and the PCE of 4.24%, which were improved by 31% and 37%, respectively comparing with the reference devices without a TiO 2 buffer layer. The stability measurement showed that PSC devices with a TiO 2 NPs buffer layer could retain 80% of the original PCE s after exposed in air for 200 h, much better than the devices without such a buffer layer. The effect can be attributed to the protection by the buffer layer against oxygen and H 2 O diffusion into the active layers. The observations indicate that TiO 2 NPs synthesized by facile solution-based method have great potential applications in PSCs, especially for large-area printed PSCs.