On the problem of open circuit voltage in metal phthalocyanine/C60 organic solar cells

Department of Physics, Kyung Hee University, 1-Hoegi-dong, Dongdaemun-gu, Seoul 130-701, Korea

Adv. Mater. Lett., 2012, 2 (1), pp 3-11

DOI: 10.5185/amlett.2010.12186

Publication Date (Web): Apr 08, 2012

Copyright © IAAM-VBRI Press

E-mail: rbpode@khu.ac.kr

Abstract

The open circuit voltage (V_OC) plays a crucial role in determining the efficiency of organic solar cells. Models of the V_OC based on (i) the energy difference between the LUMO of the acceptor material and the HOMO of the donor material at the heterointerface and (ii) chemical potential gradient which depends on the carrier mobility in a bilayer cell, are inadequate to understand the exact origin of the  VOC.  In this review article,  the  V_OC in various planar and non-planar metal phthalocyanine/C60 solar cells are analyzed. These results are compared in  CuPc/C60 and  SubPc/C60 solar cells as a representative case of the planar and non-planar metal phthalocyanine/C60 solar cells, respectively. Regardless of unfavorable characteristics of SubPc films, the VOC value of 0.92 to 0.98V in SubPc (13 nm)/C60 (33-32.5 nm) compared to 0.44 to 0.49V in CuPc (20-40 nm)/C60 (40-30 nm) solar cells was noticed. It is suggested that the structure, morphology,   and absorption properties of the evaporated film of the donor materials and the efficient separation of charges at the donor/acceptor interface in bilayer planar and non-planar metal phthalocyanine/C60 solar cells are also imperative in determining the V_OC.

Keywords

Organic solar cells, metal phthalocynaine/C60 structure, open circuit voltage (V_OC).