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Enhanced Fill Factor of Tandem Organic Solar Cells Incorporating a Diketopyrrolopyrrole‐Based Low‐Bandgap Polymer and Optimized Interlayer
Author(s) -
Wang Dong Hwan,
Kyaw Aung Ko Ko,
Park Jong Hyeok
Publication year - 2015
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201402833
Subject(s) - pedot:pss , materials science , band gap , polymer solar cell , energy conversion efficiency , tandem , chemical engineering , polystyrene sulfonate , open circuit voltage , polymer , nanoparticle , active layer , conductive polymer , annealing (glass) , nanotechnology , optoelectronics , layer (electronics) , composite material , voltage , physics , quantum mechanics , engineering , thin film transistor
We demonstrate that reproducible results can be obtained from tandem solar cells based on the wide‐bandgap poly[ N ‐9′‐heptadecanyl‐2,7‐carbazole‐alt‐5,5‐(4,7‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole] (PCDTBT) and the diketopyrrolopyrrole (DPP)‐based narrow bandgap polymer (DT‐PDPP2T‐TT) with a decyltetradecyl (DT) and an electron‐rich 2,5‐di‐2‐thienylthieno[3,2‐b]thiophene (2T‐TT) group fabricated using an optimized interlayer (ZnO NPs/ph‐n‐PEDOT:PSS) [NPs: nanoparticles; ph‐n: pH‐neutral PEDOT: poly(3,4‐ethylenedioxythiophene); PSS: polystyrene sulfonate]. The tandem cells are fabricated by applying a simple process without thermal annealing. The ZnO NP interlayer operates well when the ZnO NPs are dispersed in 2‐methoxyethanol, as no precipitation and chemical reactions occur. In addition to the ZnO NP film, we used neutral PEDOT:PSS as a second interlayer which is not affect to the sequential deposited bulk heterojunction (BHJ) active layer of acidification. The power conversion efficiency (PCE) of a tandem device reaches 7.4 % (open‐circuit voltage V OC =1.53 V, short‐circuit current density J SC =7.3 mA cm −2 , and fill factor FF =67 %). Furthermore, FF is increased to up to 71 % when another promising large bandgap (bandgap ∼1.94 eV) polymer (PBnDT‐FTAZ) is used. The surface of each layer with nanoscale morphology (BHJ1/ZnO NPs film/ph‐n‐PEDOT:PSS/BHJ2) was examined by means of AFM analysis during sequential processing. The combination of these factors, efficient DPP‐based narrow bandgap material and optimized interlayer, leads to the high FF (average approaches 70 %) and reproducibly operating tandem BHJ solar cells.