Comparing the Device Physics and Morphology of Polymer Solar Cells Employing Fullerenes and Non-Fullerene Acceptors
AuthorsBloking, Jason T.
Higgs, Andrew T.
Ponec, Andrew J.
Hoke, Eric T.
McGehee, Michael D.
KAUST Grant NumberKUS-C1–015–21
MetadataShow full item record
AbstractThere is a need to find electron acceptors for organic photovoltaics that are not based on fullerene derivatives since fullerenes have a small band gap that limits the open-circuit voltage (VOC), do not absorb strongly and are expensive. Here, a phenylimide-based acceptor molecule, 4,7-bis(4-(N-hexyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole (HPI-BT), that can be used to make solar cells with VOC values up to 1.11 V and power conversion efficiencies up to 3.7% with two thiophene polymers is demonstrated. An internal quantum efficiency of 56%, compared to 75-90% for polymer-fullerene devices, results from less efficient separation of geminate charge pairs. While favorable energetic offsets in the polymer-fullerene devices due to the formation of a disordered mixed phase are thought to improve charge separation, the low miscibility (<5 wt%) of HPI-BT in polymers is hypothesized to prevent the mixed phase and energetic offsets from forming, thus reducing the driving force for charges to separate into the pure donor and acceptor phases where they can be collected. A small molecule electron acceptor, 4,7-bis(4-(N-hexyl-phthalimide)vinyl)benzo[c]1,2,5-thiadiazole (HPI-BT), achieves efficiencies of 3.7% and open-circuit voltage values of 1.11 V in bulk heterojunction (BHJ) devices with polythiophene donor materials. The lower internal quantum efficiency (56%) in these non-fullerene acceptor devices is attributed to an absence of the favorable energetic offsets resulting from nanoscale mixing of donor and acceptor found in comparable fullerene-based devices. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
CitationBloking JT, Giovenzana T, Higgs AT, Ponec AJ, Hoke ET, et al. (2014) Comparing the Device Physics and Morphology of Polymer Solar Cells Employing Fullerenes and Non-Fullerene Acceptors. Adv Energy Mater 4: n/a–n/a. Available: http://dx.doi.org/10.1002/aenm.201301426.
SponsorsThe authors would like to thank S. Himmelberger from Stanford University for his efforts in preparing field effect transistor devices from spin-coated HPI-BT films. They also thank T. Burke, K. Graham, S. Sweetnam, Z. Beiley, J. Bartelt and A. Salleo for fruitful discussions regarding the morphological model presented here. This work was supported by funds provided by the Global Climate and Energy Project (GCEP) Award No. 1138721 and by the Center for Advanced Molecular Photovoltaics (CAMP), Award No. KUS-C1–015–21 made by the King Abdullah University of Science and Technology.
JournalAdvanced Energy Materials