Can morphology tailoring improve the open circuit voltage of organic solar cells?

Biswajit Ray, Purdue University - Main Campus
M. S. Lundstrom, Purdue University School of Electrical Engineering
Muhammad A. Alam, Birck Nanotechnology Center, Purdue University

Date of this Version



Applied Physics Letters: Volume 100, Issue 1


Copyright (2011) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters: Volume 100, Issue 1 and may be found at The following article has been submitted to/accepted by Applied Physics Letters. Copyright (2012) Biswajit Ray, Mark S. Lundstrom, and Muhammad A. Alam. This article is distributed under a Creative Commons Attribution 3.0 Unported License.


While the effect of interfacial morphology on the short circuit current (ISC) of organic photovoltaic devices (OPVs) is well known, its impact on open circuit voltage (VOC) and fill-factor (FF) are less clear. Since the output power of a solar cell Pout = ISCVOCFF, such understanding is critical for designing high-performance, morphology-engineered OPVs. In this letter, we provide an explicit analytical proof that any effort to radically improve VOC by tailoring bulk heterojunction morphology is futile, because any increase in ISC due to larger interface area is counterbalanced by corresponding increase in recombination current, so that the upper limit of VOC(BHJ) cannot exceed that of the corresponding planar heterojunction devices, i.e., VOC(BHJ) < VOC(PHJ). We discuss the implication of this VOC-constraint on the efficiency optimization of organic solar cells.


Electronic Devices and Semiconductor Manufacturing | Polymer Science | Power and Energy