skip to main content

Title: Evaluation of internal potential distribution and carrier extraction properties of organic solar cells through Kelvin probe and time-of-flight measurements

The carrier extraction property of a prototypical small molecule organic solar cell (OSC) composed of copper phthalocyanine (CuPc), C⁶⁰, and bathocuproine (BCP) was studied on the basis of the internal potential distribution and carrier dynamics in the device. The internal potential distribution in the OSC structure at the interfaces and in the bulk region was determined by the Kelvin probe method. Significant potential gradients were found in the CuPc film on indium tin oxide and in the C⁶⁰ film on CuPc, consistent with charge transfer through the contacts. Moreover, surface potential of the BCP layer grew linearly with increasing film thickness with a slope of ca. 35 mV/nm (giant surface potential: GSP), which indicated spontaneous orientation polarization in the film. The potential gradient and GSP significantly changed the built-in potential of the device. Current–voltage and modified time-of-flight measurements revealed that the BCP layer worked as an electron injection and extraction layer despite the wide energy gap. These results were discussed based on the contributions of GSP and the gap states in the BCP layer.
Authors:
; ;  [1] ; ;  [1] ;  [2] ; ;  [3]
  1. Graduate School of Advanced Integration Science, Chiba University, Chiba 263-8522 (Japan)
  2. (Japan)
  3. Advanced Technology Research Laboratories, Idemitsu Kosan Co., Ltd. Sodegaura 299-0293 (Japan)
Publication Date:
OSTI Identifier:
22306020
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 11; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CARRIERS; COPPER COMPLEXES; DISTRIBUTION; ELECTRIC POTENTIAL; ELECTRON BEAM INJECTION; ENERGY GAP; EVALUATION; EXTRACTION; FILMS; FULLERENES; INTERFACES; LAYERS; MOLECULES; ORGANIC SOLAR CELLS; PHTHALOCYANINES; POLARIZATION; SURFACE POTENTIAL; THICKNESS; TIME-OF-FLIGHT METHOD; TIN OXIDES