Electro-optical characterization and analysis of
CuPc-based solar cells with high photovoltage
V P SINGH,
R
Electrical and Computer Engineering Department and Center
for Nanoscale
Science and Engineering,
E-mail: vsingh@engr.uky.edu
Abstract. Organic
solar cells using the CuPc and PTCBI semiconductor
layers were studied. A high open circuit voltage of 1.15 V was obtained in a
device with ITO/ PEDOT:PSS/CuPc
(15 nm)/PTCBI (7 nm)/Al structure. Results were interpreted in terms of a
modified CuPc--Al Schottky
diode for the thin PTCBI case and a CuPc--PTCBI heterojunction for the thick PTCBI case. Also, the
formation of a thin aluminum oxide layer under the aluminum electrode was
postulated. This layer has a beneficial
aspect wherein shunting losses are reduced and a high photovoltage
is enabled. However, it adds greatly to the series resistance to a point where
the short circuit current density is reduced.
CuPc Schottky diodes
with an ITO/PEDOT:PSS/CuPc/Al
structure yielded a high $V_{\rm oc}$
of 900 mV for a CuPc layer of thickness 140 nm. The $V_{\rm oc}$ increased with increase
in CuPc layer thickness.
Keywords. Organic
semiconductors; photovoltaics; heterojunctions;
Schottky diodes.
PACS Nos 71.20.Rv; 72.40.+w; 73.50.Pz