Spectral Splitting Geometries for High Efficiency Multijunction Organic Solar Cells
Miquel Casademont-Viñas a, Martí Gibert-Roca a, Quan Liu b, Koen Vandewal b, Alejandro R. Goñi a c, Mariano Campoy-Quiles a
a Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Spain, Campus UAB, Bellaterra, Spain
b U Hasselt – Hasselt University, Institute for Materials Research (IMO-IMOMEC), BE, Agoralaan – Building D, Diepenbeek, Belgium
c Catalan Institution for Research and Advanced Studies (ICREA), Passeig Lluïs Companys, 23, 08010, Barcelona, Spain
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Oral, Miquel Casademont-Viñas, presentation 029
DOI: https://doi.org/10.29363/nanoge.hopv.2022.029
Publication date: 20th April 2022

Single-junction organic solar cells (OSC) nowadays reach a power conversion efficiency of 19%.[1] In principle, multi-junction devices promise a reduction of thermalization losses and thus higher efficiencies. Nevertheless, state-of-the-art multi-junction OSC, leaded by the tandem approach in which two single junction devices are stacked on top of each other, exhibit, thus far, similar efficiency values.[2] This is attributed to the challenges that arise when solution processing stackable layers, as well as the need for either a current matching or an extra transparent electrode.[2]

In this talk, we will present a new multi-junction in-plane spectral splitting geometry that we call Rainbow solar cells. In this geometry, a series of sub-cells are placed next to each other laterally, avoiding the limitations arising from stacking cells in a vertical tandem. The fabricated n-terminal devices are capable of extracting the maximum power of each sub-cell without the need for any current matching. First, we will present the advantages and disadvantages of Rainbow OSCs with respect to other organic and inorganic multi-junction approaches. Then, we use device simulations to provide design rules for increased efficiency in a Rainbow configuration. Finally experimental results are shown for PM6:IO-4Cl and PTB7-Th:COTIC-4F blends, as high and low band-gap sub-cells, respectively. The results, in agreement with simulations, demonstrate an efficiency increase of around 30% of the Rainbow geometry with respect to the best single junction device.

The Spanish "Ministerio de Ciencia e Innovación (MICINN)" is gratefully acknowledged for its support through grants No. SEV-2015-0496 (FUNMAT) and CEX2019-000917-S (FUNFUTURE) in the framework of the Spanish Severo Ochoa Centre of Excellence program and the AEI/FEDER(UE) grant PGC2018-095411-B-100 (RAINBOW). The authors also thank the Catalan agency AGAUR for grant 2017-SGR-00488 and the National Network "Red Perovskitas" (MICINN funded). MCV acknowledges a FPI fellowship (PRE2019-089855) from. MCV and MGR acknowledges the PhD programme in Materials Science from Universitat Autònoma de Barcelona in which they were enrolled. Financial support is also acknowledged from the European Research Council through project ERC CoG648901 (FOREMAT).

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