@article{KimberWrightO'Kaneetal.2012,
  author    = {Kimber, Robin G. E. and Wright, Edward N. and O'Kane, Simon E. J. and Walker, Alison B. and Blakesley, James C.},
  title     = {Mesoscopic kinetic Monte Carlo modeling of organic photovoltaic device characteristics},
  series = {Physical review : B, Condensed matter and materials physics},
  volume    = {86},
  journal   = {Physical review : B, Condensed matter and materials physics},
  number    = {23},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {1098-0121},
  doi       = {10.1103/PhysRevB.86.235206},
  pages     = {9},
  year      = {2012},
  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 x 10(7) s(-1). 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.},
  language  = {en}
}
@article{GaoWangBlakesleyetal.2012,
  author    = {Gao, Feng and Wang, Jianpu and Blakesley, James C. and Hwang, Inchan and Li, Zhe and Greenham, Neil C.},
  title     = {Quantifying loss mechanisms in polymer Fullerene photovoltaic devices},
  series = {dvanced energy materials},
  volume    = {2},
  journal   = {dvanced energy materials},
  number    = {8},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1614-6832},
  doi       = {10.1002/aenm.201200073},
  pages     = {956 -- 961},
  year      = {2012},
  language  = {en}
}
@article{AlbrechtSchindlerKurpiersetal.2012,
  author    = {Albrecht, Steve and Schindler, Wolfram and Kurpiers, Jona and Kniepert, Juliane and Blakesley, James C. and Dumsch, Ines and Allard, Sybille and Fostiropoulos, Konstantinos and Scherf, Ullrich and Neher, Dieter},
  title     = {On the field dependence of free charge carrier generation and recombination in blends of PCPDTBT/PC70BM influence of solvent additives},
  series = {The journal of physical chemistry letters},
  volume    = {3},
  journal   = {The journal of physical chemistry letters},
  number    = {5},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1948-7185},
  doi       = {10.1021/jz3000849},
  pages     = {640 -- 645},
  year      = {2012},
  abstract  = {We have applied time-delayed collection field (TDCF) and charge extraction by linearly increasing voltage (CELIV) to investigate the photogeneration, transport, and recombination of charge carriers in blends composed of PCPDTBT/PC70BM processed with and without the solvent additive diiodooctane. The results suggest that the solvent additive has severe impacts on the elementary processes involved in the photon to collected electron conversion in these blends. First, a pronounced field dependence of the free carrier generation is found for both blends, where the field dependence is stronger without the additive. Second, the fate of charge carriers in both blends can be described with a rather high bimolecular recombination coefficients, which increase with decreasing internal field. Third, the mobility is three to four times higher with the additive. Both blends show a negative field dependence of mobility, which we suggest to cause bias-dependent recombination coefficients.},
  language  = {en}
}
@article{AlSa'diJaiserBagnichetal.2012,
  author    = {Al-Sa'di, Mahmoud and Jaiser, Frank and Bagnich, Sergey A. and Unger, Thomas and Blakesley, James C. and Wilke, Andreas and Neher, Dieter},
  title     = {Electrical and optical simulations of a polymer-based phosphorescent organic light-emitting diode with high efficiency},
  series = {Journal of polymer science : B, Polymer physics},
  volume    = {50},
  journal   = {Journal of polymer science : B, Polymer physics},
  number    = {22},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0887-6266},
  doi       = {10.1002/polb.23158},
  pages     = {1567 -- 1576},
  year      = {2012},
  abstract  = {A comprehensive numerical device simulation of the electrical and optical characteristics accompanied with experimental measurements of a new highly efficient system for polymer-based light-emitting diodes doped with phosphorescent dyes is presented. The system under investigation comprises an electron transporter attached to a polymer backbone blended with an electronically inert small molecule and an iridium-based green phosphorescent dye which serves as both emitter and hole transporter. The device simulation combines an electrical and an optical model. Based on the known highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of all components as well as the measured electrical and optical characteristics of the devices, we model the emissive layer as an effective medium using the dye's HOMO as hole transport level and the polymer LUMO as electron transport level. By fine-tuning the injection barriers at the electron and hole-injecting contact, respectively, in simulated devices, unipolar device characteristics were fitted to the experimental data. Simulations using the so-obtained set of parameters yielded very good agreement to the measured currentvoltage, luminancevoltage characteristics, and the emission profile of entire bipolar light-emitting diodes, without additional fitting parameters. The simulation was used to gain insight into the physical processes and the mechanisms governing the efficiency of the organic light-emitting diode, including the position and extent of the recombination zone, carrier concentration profiles, and field distribution inside the device. The simulations show that the device is severely limited by hole injection, and that a reduction of the hole-injection barrier would improve the device efficiency by almost 50\%.},
  language  = {en}
}