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- Inverted solar cells (1)
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- PCPDTBT (1)
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/cm², 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 ~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.