David

Publication date: November 2017
Source:Organic Electronics, Volume 50
Author(s): Jeroen Brebels, Karine C.C.W.S. Klider, Mathias Kelchtermans, Pieter Verstappen, Melissa Van Landeghem, Sabine Van Doorslaer, Etienne Goovaerts, Jarem R. Garcia, Jean Manca, Laurence Lutsen, Dirk Vanderzande, Wouter Maes
Although research in the field of organic photovoltaics (OPV) still merely focuses on efficiency, efforts to increase the sustainability of the production process and the materials encompassing the device stack are of equally crucial importance to fulfil the promises of a truly renewable source of energy. In this study, a number of steps in this direction are taken. The photoactive polymers all contain an electron-deficient building block inspired on the natural indigo dye, bay-annulated indigo, combined with electron-rich thiophene and 4H-dithieno[3,2-b:2′,3′-d]pyrrole units. The synthetic protocol (starting from indigo) is optimized and the final materials are thoroughly analyzed. MALDI-TOF mass spectrometry provides detailed information on the structural composition of the polymers. Best solar cell efficiencies are obtained for polymer:fullerene blends spin-coated from a pristine non-halogenated solvent (o-xylene), which is highly recommended to reduce the ecological footprint of OPV and is imperative for large scale production and commercialization.

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Publication date: November 2017
Source:Organic Electronics, Volume 50
Author(s): Xin-Yan Zhao, Ting Wang, Lu Wang, Xiangyu Zhang, Zui Tao, Bao Xiu Mi, Zhi Qiang Gao
Tetra-nuclear Zinc(II) complex Zn4O(AID)6 [AID = 7-azaindolate] is a wide band gap luminescent material that exhibits efficient emission matching the absorption spectra of organic donor materials such as polythiophene (P3HT). This work demonstrates polymer solar cells (PSC) based on P3HT:PCBM (phenyl-C61-butyric acid methyl ester) blend active layer with a Zn4O(AID)6 cathode interfacial layer achieving a power conversion efficiency (PCE) significantly higher than that of the reference devices. The energy level and impedance spectroscopy analysis show that the Zn4O(AID)6 cathode interfacial layer acts as an efficient exciton/hole blocking layer, and reduces charge recombination rate with more efficient electron extraction. The Zn4O(AID)6 interfacial layer also helps achieve longer lifetime of PSC devices. The improved efficiency and stability combined with low cost and nontoxicity of Zn4O(AID)6 make it a promising cathode interfacial material for high-performance and stable PSC devices.

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Publication date: November 2017
Source:Organic Electronics, Volume 50
Author(s): Mushfika Baishakhi Upama, Naveen Kumar Elumalai, Md Arafat Mahmud, Dian Wang, Faiazul Haque, Vinicius R. Gonçales, J. Justin Gooding, Matthew Wright, Cheng Xu, Ashraf Uddin
High performance, hysteresis-free, low temperature n-i-p perovskite solar cells are successfully fabricated by solution processing using fullerene electron transport layer (ETL). PC71BM fullerene, with broader absorption spectrum and lower HOMO level, when incorporated in the perovskite solar cell yielded average power conversion efficiency (PCE) of 13.9%. This is the highest reported PCE in n-i-p perovskite solar cells with PC71BM ETL. The devices exhibited negligible hysteresis and high open-circuit voltage (Voc). On the contrary, devices with PC61BM, a common fullerene ETL in perovskite solar cell, exhibited large hysteresis and lower Voc. The underlying mechanisms of superior performance of devices with PC71BM ETL were found to be correlated with fullerene surface wettability and perovskite grain size. The influence of fullerene ETL on the perovskite grain growth and subsequent photovoltaic performance was investigated by contact angle measurement, morphological characterization of the surface topography and electrochemical impedance analysis.

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ACS Applied Materials & Interfaces DOI: 10.1021/am3026739