Issue 12, 2016

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

Abstract

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 JK-216D, and almost no change for JK-217D, 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.

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

Supplementary files

Article information

Article type
Paper
Submitted
21 Aug. 2015
Accepted
12 Okt. 2015
First published
12 Okt. 2015

Nanoscale, 2016,8, 6335-6340

Author version available

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

S. Paek, M. A. Rub, H. Choi, S. A. Kosa, K. A. Alamry, J. W. Cho, P. Gao, J. Ko, A. M. Asiri and M. K. Nazeeruddin, Nanoscale, 2016, 8, 6335 DOI: 10.1039/C5NR05697G

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