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Abstract title Towards large-scale solution processing of tandem solar cells: assessing the potential of high performance polymer donors for multi-junction applications
Author Dr. Li, N., I-MEET, FAU Erlangen-N├╝rnberg, Erlangen, Germany (Presenting author)
Co-author(s) Brabec, C.J.
Abstract text

The tandem concept is especially attractive for organic photovoltaics (OPV) owing to its potential to significantly improve the power conversion efficiency (PCE) of OPV single cells by ~40%.1 The performance of organic tandem solar cells is directly determined by the functionality and reliability of intermediate (interconnection) layer as well as the photovoltaic properties of spectrally-matched sub-cells. The intermediate layer on the one hand is responsible for selectively collecting charge carriers from sub-cells, and on the other hand has to facilitate efficient charge recombination at its inner interface. Although many OPV systems have been developed to obtain remarkable PCE of 10-12%, only very few candidates have been investigated and characterized in the tandem configurations. Furthermore, the required information for large-scale mass production was barely explored, such as roll-to-roll compatibility, environmental resistivity, device operational stability, etc.

In this contribution, we will demonstrate interface and architecture design rules for solution-processed organic tandem solar cells towards large-scale production. A solution-processed hybrid hole-transporting layer consisting of MoOx nanoparticles and PEDOT:PSS is engineered to be fully compatible with state-of-the-art OPV systems, and can be further applied in combination with ZnO for high-performance organic tandem solar cells.2 Moreover, a series of high-performance polymer donors, such as PTB7-Th (PCE10) and PffBT4T-2OD (PCE11) are investigated and analysed to assess their applicability for large-scale mass production.3,4 Organic tandem solar cells with all the semiconducting layers printed in air at fairly low temperatures achieve a high PCE over 10% along with an unprecedented high fill factor >76%.

[1] N. Li et al., Adv. Energy Mater. 2014, 4, 1400084. [2] X. Du et al., Adv. Energy Mater. 2017, 7, 1601959. [3] N. Li et al., Energy Environ. Sci. 2015, 8, 2902. [4] N. Li et al., Nat. Commun. 2017, 8, 14541.