Bithiophene-Based Interfacial Layer for High-Efficiency Bulk-Heterojunction Organic Photovoltaic Cells

Northwestern researchers have developed a new technology that improves bulk-heterojunction (BHJ) organic photovoltaic (OPV) cells. They designed a new interfacial hole transport/electron-blocking layer for BHJ OPV cells. This layer improves upon the commonly used PEDOT:PSS layer and significantly improves the performance of P3HT:PCBM BHJ solar cells. Recently the same researchers presented a novel interfacial layer (IFL) consisting of a TFB: TPDSi2 which significantly improves BHJ solar cell devices on multiple fronts. It displays superior charge blocking characteristics thermal stability and adhesion to the ITO surface compared to PEDOT:PSS. It also maintains high hole mobility good optical transparency throughout the visible region of the spectrum and insolubility towards organic solvents which allows active layer deposition by spin-coating. However the HOMO energy level of TPDSi2 is not well suited for use with higher efficiency P3HT:PCBM BHJ systems due to a mismatch between TPDSi2 and P3HT HOMO energies. The energy mismatch creates a barrier to hole transport from the P3HT through the TPDSi2 to the anode. This current invention provides a solution by describing the synthesis characterization and implementation of an energetically tuned IFL precursor PABTSi2 as a component in P3HT:PCBM BHJ OPVs. This novel IFL material optimizes hole transport to the cell anode. When incorporated into P3HT:PCBM OPVs the robust cross-linked PABTSi2:TFB IFL strongly binds to the hydroxylated ITO surface and provides solar power conversion efficiencies that are comparable to those of heavily optimized PEDOT:PSS-based devices. Applications: 1) Organic photovoltaic cells 2) BHJ solar cells IP Status: Issued US Patent No. 8399761


1) Increased organic photovoltaic efficiency 2) Optimizes hole transport to the cell anode 3) Enhanced device stability

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