Transport and optical gaps and energy band alignment at organic-inorganic interfaces

DA Evans, AR Vearey-Roberts, OR Roberts, GT Williams, SP Cooil, DP Langstaff, G Cabailh, IT McGovern and JP Goss
Journal of Applied Physics

The transport and optical band gaps for the organic semiconductor tin (II) phthalocyanine (SnPc) and the complete energy band profiles have been determined for organic-inorganic interfaces between SnPc and III-V semiconductors. High throughput measurement of interface energetics over timescales comparable to the growth rates was enabled using in situ and real-time photoelectron spectroscopy combined with Organic Molecular Beam Deposition. Energy band alignment at SnPc interfaces with GaAs, GaP, and InP yields interface dipoles varying from −0.08 (GaP) to −0.83 eV (GaAs). Optical and transport gaps for SnPc and CuPc were determinedfrom photoelectron spectroscopy and from optical absorption using spectroscopic ellipsometry to complete the energy band profiles. For SnPc, the difference in energy between the optical and transport gaps indicates an exciton binding energy of (0.66±0.3) eV.

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