TY  - JOUR
A1  - Albrecht, Steve
A1  - Schaefer, Sebastian
A1  - Lange, Ilja
A1  - Yilmaz, Seyfullah
A1  - Dumsch, Ines
A1  - Allard, Sybille
A1  - Scherf, Ullrich
A1  - Hertwig, Andreas
A1  - Neher, Dieter
T1  - Light management in PCPDTBT:PC70BM solar cells: A comparison of standard and inverted device structures
JF  - Organic electronics : physics, materials and applications
N2  - We compare standard and inverted bulk heterojunction solar cells composed of PCPDTBT:PC70BM blends. Inverted devices comprising 100 nm thick active layers exhibited short circuit currents of 15 mA/cm(2), 10% larger than in corresponding standard devices. Modeling of the optical field distribution in the different device stacks proved that this enhancement originates from an increased absorption of incident light in the active layer. Internal quantum efficiencies (IQEs) were obtained from the direct comparison of experimentally derived and modeled currents for different layer thicknesses, yielding IQEs of similar to 70% for a layer thickness of 100 nm. Simulations predict a significant increase of the light harvesting efficiency upon increasing the layer thickness to 270 nm. However, a continuous deterioration of the photovoltaic properties with layer thickness was measured for both device architectures, attributed to incomplete charge extraction. On the other hand, our optical modeling suggests that inverted devices based on PCPDTBT should be able to deliver high power conversion efficiencies (PCEs) of more than 7% provided that recombination losses can be reduced.
KW  - Organic solar cells
KW  - Inverted solar cells
KW  - PCPDTBT
KW  - Low band-gap
KW  - Optical modeling
Y1  - 2012
U6  - https://doi.org/10.1016/j.orgel.2011.12.019
SN  - 1566-1199
VL  - 13
IS  - 4
SP  - 615
EP  - 622
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Lange, Ilja
A1  - Kniepert, Juliane
A1  - Pingel, Patrick
A1  - Dumsch, Ines
A1  - Allard, Sybille
A1  - Janietz, Silvia
A1  - Scherf, Ullrich
A1  - Neher, Dieter
T1  - Correlation between the open circuit voltage and the energetics of organic bulk heterojunction solar cells
JF  - The journal of physical chemistry letters
N2  - A detailed investigation of the open circuit voltage (V-OC) of organic bulk heterojunction solar cells comprising three different donor polymers and two different fullerene-based acceptors is presented. Bias amplified charge extraction (BACE) is combined with Kelvin Probe measurements to derive information on the relevant energetics in the blend. On the example of P3HT:PC70BM the influence of composition and preparation conditions on the relevant transport levels will be shown. Moderate upward shifts of the P3HT HOMO depending on crystallinity are observed, but contrarily to common believe, the dependence of V-OC on blend composition and thermal history is found to be largely determined by the change in the PCBM LUMO energy. Following this approach, we quantified the energetic contribution to the V-OC in blends with fluorinated polymers or higher adduct fullerenes.
Y1  - 2013
U6  - https://doi.org/10.1021/jz401971e
SN  - 1948-7185
VL  - 4
IS  - 22
SP  - 3865
EP  - 3871
PB  - American Chemical Society
CY  - Washington
ER  -