ELECTROSTATIC PHENOMENA AT DONOR-ACCEPTOR INTERFACE OF ORGANIC SEMICONDUCTORS STUDIED BY IN-SITU OPTICAL SECOND-HARMONIC GENERATION MEASUREMENT

摘要

Optical second-harmonic generation (SHG) measurement was conducted to study the electrostatic phenomena at donor-acceptor interface of organic semiconductors. SHG signal was monitored in-situ during successive deposition of C_(60) and pentacene layer. SHG intensity monotonously increased during the C_(60) deposition and drastically decreased immediately after pentacene deposition started. This decrease is attributed to the formation of dipole layer at the interface between C_(60) and pentacene due to the displacement of charge. Theoretical simulation of the thickness dependence of the SHG intensity also supports the presence of the dipole layer. In-situ observation also indicates that insertion of insulating layer between donor and acceptor layer inhibits the dipole layer formation.