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

NU 2009-044

Inventors

Alexander Hains

Tobin Marks*

Abstract

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