Triptycene as a supramolecular additive in PTB7:PCBM blends and its influence on photovoltaic properties
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Additives play an important role in modifying the morphology and phase separation of donor and acceptor molecules in bulk heterojunction (BHJ) solar cells. Here, we report triptycene (TPC) as a small-molecule additive for supramolecular control of phase separation and concomitant improvement of the power conversion efficiency (PCE) of PTB7 donor and fullerene acceptor-based BHJ polymer solar cells. An overall 60% improvement in PCE is observed for both PTB7:PC61BM and PTB7:PC71BM blends. The improved photovoltaic (PV) performance can be attributed to three factors: (a) TPC-induced supramolecular interactions with donor:acceptor components in the blends to realize a nanoscale phase-separated morphology; (b) an increase in the charge transfer state energy that lowers the driving force for electron transfer from donor to acceptor molecules; and (c) an increase in the charge carrier mobility. An improvement in efficiency using TPC as a supramolecular additive has also been demonstrated for other BHJ blends such as PBDB-T:PC71BM and P3HT:PCBM, implying the wide applicability of this new additive molecule. A comparison of the photostability of TPC as an additive for PTB7:PCBM solar cells to that of the widely used 1,8-diiodooctane additive shows ∼30% higher retention of PV performance for the TPC-added solar cells after 34 h of AM 1.5G illumination. The results obtained suggest that the approach of using additives that can promote supramolecular interactions to modify the length scale of phase separation between donor and acceptor is very promising and can lead to the development of highly efficient and stable organic photovoltaics.
Krishnan Jagadamma , L , McCarron , L , A. Wiles , A , Savikhin , V , Sajjad , M T , Yazdani , M , M Rotello , V , F Toney , M , Cooke , G & Samuel , I D W 2018 , ' Triptycene as a supramolecular additive in PTB7:PCBM blends and its influence on photovoltaic properties ' , ACS Applied Materials & Interfaces , vol. 10 , no. 29 , pp. 24665-24678 . https://doi.org/10.1021/acsami.8b03114
ACS Applied Materials & Interfaces
Copyright © 2018 American Chemical Society. This work has been made available online in accordance with publisher policies or with permission. Permission for further reuse of this content should be sought from the publisher or the rights holder. This is the author created accepted manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at https://doi.org/10.1021/acsami.8b03114
DescriptionWe acknowledge support from EPSRC (grant number EP/L012294/1) and the European Research Council (grant number 321305). I. D. W. S. also acknowledges a Royal Society Wolfson Research Merit Award.
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