TY  - JOUR
A1  - Gao, Feng
A1  - Wang, Jianpu
A1  - Blakesley, James C.
A1  - Hwang, Inchan
A1  - Li, Zhe
A1  - Greenham, Neil C.
T1  - Quantifying loss mechanisms in polymer Fullerene photovoltaic devices
JF  - dvanced energy materials
KW  - organic photovoltaics
KW  - recombination
KW  - bulk heterojunctions
KW  - loss mechanisms
KW  - drift-diffusion models
Y1  - 2012
U6  - https://doi.org/10.1002/aenm.201200073
SN  - 1614-6832
VL  - 2
IS  - 8
SP  - 956
EP  - 961
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Yazmaciyan, Aren
A1  - Stolterfoht, Martin
A1  - Burn, Paul L.
A1  - Lin, Qianqian
A1  - Meredith, Paul
A1  - Armin, Ardalan
T1  - Recombination losses above and below the transport percolation threshold in bulk heterojunction organic solar cells
JF  - Advanced energy materials
N2  - Achieving the highest power conversion efficiencies in bulk heterojunction organic solar cells requires a morphology that delivers electron and hole percolation pathways for optimized transport, plus sufficient donor:acceptor contact area for near unity charge transfer state formation. This is a significant structural challenge, particularly in semiconducting polymer:fullerene systems. This balancing act in the model high efficiency PTB7:PC70BM blend is studied by tuning the donor:acceptor ratio, with a view to understanding the recombination loss mechanisms above and below the fullerene transport percolation threshold. The internal quantum efficiency is found to be strongly correlated to the slower carrier mobility in agreement with other recent studies. Furthermore, second-order recombination losses dominate the shape of the current density-voltage curve in efficient blend combinations, where the fullerene phase is percolated. However, below the charge transport percolation threshold, there is an electric-field dependence of first-order losses, which includes electric-field-dependent photogeneration. In the intermediate regime, the fill factor appears to be limited by both first- and second-order losses. These findings provide additional basic understanding of the interplay between the bulk heterojunction morphology and the order of recombination in organic solar cells. They also shed light on the limitations of widely used transport models below the percolation threshold.
KW  - bulk heterojunctions
KW  - charge transport
KW  - organic solar cells
KW  - percolation threshold
KW  - recombination losses
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201703339
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 18
PB  - Wiley-VCH
CY  - Weinheim
ER  -