A dual-functional asymmetric squaraine-based low band gap hole transporting material for efficient perovskite solar cells

We demonstrate for the first time an asymmetric squaraine-based low band-gap hole transporting material, which acted as both light harvesting and hole transporting layers in methylammonium lead triiodide perovskite solar cells. Opto-electrochemical characterization revealed extremely high molar exti...

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Bibliographic Details
Published in:Nanoscale 2016-03, Vol.8 (12), p.6335-6340
Main Authors: Paek, Sanghyun, Rub, Malik Abdul, Choi, Hyeju, Kosa, Samia A, Alamry, Khalid A, Cho, Jin Woo, Gao, Peng, Ko, Jaejung, Asiri, Abdullah M, Nazeeruddin, Mohammad Khaja
Format: Article
Language:English
Subjects:
Asymmetry
Devices
Molecular orbitals
Perovskites
Photovoltaic cells
Solar cells
Titanium dioxide
Transporting
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Summary:We demonstrate for the first time an asymmetric squaraine-based low band-gap hole transporting material, which acted as both light harvesting and hole transporting layers in methylammonium lead triiodide perovskite solar cells. Opto-electrochemical characterization revealed extremely high molar extinction coefficients of the absorption bands in the low energy region and prominent space charge delocalization due to its electronically asymmetric nature. A suitable band alignment of the squaraine HOMO level with the valence band edge of the perovskite, and the conduction band of the TiO2 with LUMO of the perovskite allowed a cascade of hole extraction and electron injection, respectively. Red-shifted absorption was observed for both HTMs in thin films coated on the perovskite, and the optimized devices exhibited an impressive PCE of 14.7% under full sunlight illumination (100 mW cm(-2), AM1.5 G). The efficiency value is comparable to that of the devices using a state-of-the-art spiro-OMeTAD hole transport layer under similar conditions. Ambient stability after 300 h revealed that 88% of the initial efficiency remained for , and almost no change for , indicating that the devices had good long-term stability thus suggesting that the asymmetric squaraines have great potential as a dual-functional HTM for high performance perovskite solar cells.
ISSN:2040-3364
2040-3372
DOI:10.1039/c5nr05697g