Organic solar cells with crosslinked polymeric exciton blocking layer

We show that the performance of an organic solar cell can be increased by the introduction of an additional polymeric exciton blocking layer. In order to realize this, the novel polymer PFTPDAc with pendant acrylate groups is developed. Thin films are coated from a PFTPDAc solution and subsequently crosslinked by irradiation. Thereby, the film becomes completely insoluble and allows spincoating of a second polymer layer on top. We realize a three layer solar cell which contains a crosslinked PFTPDAc interlayer on top of the molybdenum oxide anode and layers of the low-bandgap polymer PCDTBT and C-60. In comparison with a reference cell without the interlayer, the EQE is significantly increased in the spectral region between 400 and 650 nm. From current-voltage measurements a power conversion efficiency of 1.8% is determined. PL measurements show that the increase of solar cell performance is attributed to exciton blocking by the PFTPDAc interlayer.