TY  - JOUR
A1  - Ran, Niva A.
A1  - Love, John A.
A1  - Heiber, Michael C.
A1  - Jiao, Xuechen
A1  - Hughes, Michael P.
A1  - Karki, Akchheta
A1  - Wang, Ming
A1  - Brus, Viktor V.
A1  - Wang, Hengbin
A1  - Neher, Dieter
A1  - Ade, Harald
A1  - Bazan, Guillermo C.
A1  - Thuc-Quyen Nguyen, 
T1  - Charge generation and recombination in an organic solar cell with low energetic offsets
JF  - dvanced energy materials
N2  - Organic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short-circuit currents (J(SC)) and fill factors (FF). However, it is necessary to reduce the energetic offsets to achieve high open-circuit voltages (V-OC). Recently, reports have highlighted BHJ blends that are pushing at the accepted limits of energetic offsets necessary for high efficiency. Unfortunately, most of these BHJs have modest FF values. How the energetic offset impacts the solar cell characteristics thus remains poorly understood. Here, a comprehensive characterization of the losses in a polymer:fullerene BHJ blend, PIPCP:phenyl-C61-butyric acid methyl ester (PC61BM), that achieves a high V-OC (0.9 V) with very low energy losses (E-loss = 0.52 eV) from the energy of absorbed photons, a respectable J(SC) (13 mA cm(-2)), but a limited FF (54%) is reported. Despite the low energetic offset, the system does not suffer from field-dependent generation and instead it is characterized by very fast nongeminate recombination and the presence of shallow traps. The charge-carrier losses are attributed to suboptimal morphology due to high miscibility between PIPCP and PC61BM. These results hold promise that given the appropriate morphology, the J(SC), V-OC, and FF can all be improved, even with very low energetic offsets.
KW  - energetic offset
KW  - fill factor
KW  - morphology
KW  - organic solar cells
KW  - recombination
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201701073
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 5
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Wang, Ming
A1  - White, Neil
A1  - Grimm, Volker
A1  - Hofman, Helen
A1  - Doley, David
A1  - Thorp, Grant
A1  - Cribb, Bronwen
A1  - Wherritt, Ella
A1  - Han, Liqi
A1  - Wilkie, John
A1  - Hanan, Jim
T1  - Pattern-oriented modelling as a novel way to verify and validate functional-structural plant models
BT  - a demonstration with the annual growth module of avocado
JF  - Annals of botany
N2  - Background and Aims Functional-structural plant (FSP) models have been widely used to understand the complex interactions between plant architecture and underlying developmental mechanisms. However, to obtain evidence that a model captures these mechanisms correctly, a clear distinction must be made between model outputs used for calibration and thus verification, and outputs used for validation. In pattern-oriented modelling (POM), multiple verification patterns are used as filters for rejecting unrealistic model structures and parameter combinations, while a second, independent set of patterns is used for validation. Key Results After calibration, our model simultaneously reproduced multiple observed architectural patterns. The model then successfully predicted, without further calibration, the validation patterns. The model supports the hypothesis that carbon allocation can be modelled as being dependent on current organ biomass and sink strength of each organ type, and also predicted the observed developmental timing of the leaf sink-source transition stage.
KW  - Pattern-oriented modelling
KW  - agent-based model
KW  - individual-based model
KW  - functional-structural plant model
KW  - model analysis
KW  - model verification
KW  - model validation
KW  - ODD (Overview, Design concepts, Details) protocol
KW  - Persea americana
KW  - plant architecture
KW  - carbon allocation
KW  - L-systems
Y1  - 2018
U6  - https://doi.org/10.1093/aob/mcx187
SN  - 0305-7364
SN  - 1095-8290
VL  - 121
IS  - 5
SP  - 941
EP  - 959
PB  - Oxford Univ. Press
CY  - Oxford
ER  -