Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics

R.G.E. Kimber, E.N. Wright, S.E.J. O'Kane, A.B. Walker, J.C. Blakesley

Research output: Contribution to journalArticle

50 Citations (Scopus)
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Abstract

Measured mobility and current-voltage characteristics of single layer and photovoltaic (PV) devices composed of poly{9,9-dioctylfluorene-co-bis[N,N -(4-butylphenyl)]bis(N,N-phenyl-1,4- phenylene)diamine} (PFB) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) have been reproduced by a mesoscopic model employing the kinetic Monte Carlo (KMC) approach. Our aim is to show how to avoid the uncertainties common in electrical transport models arising from the need to fit a large number of parameters when little information is available, for example, a single current-voltage curve. Here, simulation parameters are derived from a series of measurements using a self-consistent "building-blocks" approach, starting from data on the simplest systems. We found that site energies show disorder and that correlations in the site energies and a distribution of deep traps must be included in order to reproduce measured charge mobility-field curves at low charge densities in bulk PFB and F8BT. The parameter set from the mobility-field curves reproduces the unipolar current in single layers of PFB and F8BT and allows us to deduce charge injection barriers. Finally, by combining these disorder descriptions and injection barriers with an optical model, the external quantum efficiency and current densities of blend and bilayer organic PV devices can be successfully reproduced across a voltage range encompassing reverse and forward bias, with the recombination rate the only parameter to be fitted, found to be 1×107 s1. These findings demonstrate an approach that removes some of the arbitrariness present in transport models of organic devices, which validates the KMC as an accurate description of organic optoelectronic systems, and provides information on the microscopic origins of the device behavior.
Original languageEnglish
Article number235206
JournalPhysical Review B
Volume86
Issue number23
DOIs
Publication statusPublished - 26 Dec 2012

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Kinetics
kinetics
electric potential
curves
disorders
injection
Charge injection
Diamines
Electric potential
Current voltage characteristics
diamines
Charge density
Quantum efficiency
Optoelectronic devices
quantum efficiency
Current density
traps
current density
energy
simulation

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Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics. / Kimber, R.G.E.; Wright, E.N.; O'Kane, S.E.J.; Walker, A.B.; Blakesley, J.C.

In: Physical Review B, Vol. 86, No. 23, 235206, 26.12.2012.

Research output: Contribution to journalArticle

Kimber, R.G.E. ; Wright, E.N. ; O'Kane, S.E.J. ; Walker, A.B. ; Blakesley, J.C. / Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics. In: Physical Review B. 2012 ; Vol. 86, No. 23.
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