Universality of non-Ohmic shunt leakage in thin-film solar cells

Sourabh Dongaonkar, Purdue University - Main Campus
Jonathan D. Servaites, Northwestern University
Grayson M. Ford, Purdue University - Main Campus
Stephen Loser, Northwestern University
James E. Moore, Purdue University - Main Campus
Ryan M. Gelfand, Northwestern University
Hooman Mohseni, Northwestern University
Hugh W. Hillhouse, Purdue University - Main Campus
Rakesh Agrawal, Purdue
Mark A. Ratner, Northwestern University
Tobin J. Marks, Northwestern University
Mark Lundstrom, Purdue University
Muhammad A. Alam, Purdue University - Main Campus

Date of this Version

12-2010

Abstract

We compare the dark current-voltage (IV) characteristics of three different thin-film solar cell types: hydrogenated amorphous silicon (a-Si:H) p-i-n cells, organic bulk heterojunction (BHJ) cells, and Cu(In,Ga)Se2 (CIGS) cells. All three device types exhibit a significant shunt leakage current at low forward bias (V< ∼ 0.4) and reverse bias, which cannot be explained by the classical solar cell diode model. This parasitic shunt current exhibits non-Ohmic behavior, as opposed to the traditional constant shunt resistance model for photovoltaics. We show here that this shunt leakage (Ish), across all three solar cell types considered, is characterized by the following common phenomenological features: (a) voltage symmetry about V = 0, (b) nonlinear (power law) voltage dependence, and (c) extremely weak temperature dependence. Based on this analysis, we provide a simple method of subtracting this shunt current component from the measured data and discuss its implications on dark IV parameter extraction. We propose a space charge limited (SCL) current model for capturing all these features of the shunt leakage in a consistent framework and discuss possible physical origin of the parasitic paths responsible for this shunt current mechanism.

Discipline(s)

Electronic Devices and Semiconductor Manufacturing

 

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