Capturing Mobile Lithium Ions in a Molecular Hole Transporter Enhances the Thermal Stability of Perovskite Solar Cells

A thermally stable perovskite solar cell (PSC) based on a new molecular hole transporter (MHT) of 1,3‐bis(5‐(4‐(bis(4‐methoxyphenyl) amino)phenyl)thieno[3,2‐b]thiophen‐2‐yl)‐5‐octyl‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (coded HL38) is reported. Hole mobility of 1.36 × 10−3 cm2 V−1 s−1 and glass tra...

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Bibliographic Details
Published in:Advanced materials (Weinheim) 2021-03, Vol.33 (12), p.e2007431-n/a
Main Authors: Kim, Seul‐Gi, Le, Thi Huong, Monfreid, Thybault, Goubard, Fabrice, Bui, Thanh‐Tuân, Park, Nam‐Gyu
Format: Article
Language:English
Subjects:
Additives
Chemical Sciences
Energy conversion efficiency
Fourier transforms
Glass transition temperature
Hole mobility
hole‐transporting materials
Inorganic chemistry
interface engineering
Interface stability
Lithium
Lithium ions
Mass spectrometry
Organic chemistry
perovskite solar cells
Perovskites
Photovoltaic cells
Polymers
Solar cells
Thermal stability
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Summary:A thermally stable perovskite solar cell (PSC) based on a new molecular hole transporter (MHT) of 1,3‐bis(5‐(4‐(bis(4‐methoxyphenyl) amino)phenyl)thieno[3,2‐b]thiophen‐2‐yl)‐5‐octyl‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (coded HL38) is reported. Hole mobility of 1.36 × 10−3 cm2 V−1 s−1 and glass transition temperature of 92.2 °C are determined for the HL38 doped with lithium bis(trifluoromethanesulfonyl)imide and 4‐tert‐butylpyridine as additives. Interface engineering with 2‐(2‐aminoethyl)thiophene hydroiodide (2‐TEAI) between the perovskite and the HL38 improves the power conversion efficiency (PCE) from 19.60% (untreated) to 21.98%, and this champion PCE is even higher than that of the additive‐containing 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐MeOTAD)‐based device (21.15%). Thermal stability testing at 85 °C for over 1000 h shows that the HL38‐based PSC retains 85.9% of the initial PCE, while the spiro‐MeOTAD‐based PSC degrades unrecoverably from 21.1% to 5.8%. Time‐of‐flight secondary‐ion mass spectrometry studies combined with Fourier transform infrared spectroscopy reveal that HL38 shows lower lithium ion diffusivity than spiro‐MeOTAD due to a strong complexation of the Li+ with HL38, which is responsible for the higher degree of thermal stability. This work delivers an important message that capturing mobile Li+ in a hole‐transporting layer is critical in designing novel MHTs for improving the thermal stability of PSCs. In addition, it also highlights the impact of interface design on non‐conventional MHTs. A thermally stable perovskite solar cell is developed by capturing mobile lithium ions using a new molecular hole transporter, 1,3‐bis(5‐(4‐(bis(4‐methoxyphenyl)amino)phenyl)thieno[3,2‐b]thiophen‐2‐yl)‐5‐octyl‐4H‐thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (coded HL38), where a strong interaction of the lithium ions in lithium bis(trifluoromethanesulfonyl)imide with the 5‐octylthieno[3,4‐c]pyrrole‐4,6‐dione (octyl‐TPD) moiety in HL38 is responsible for maintaining ≈86% of the initial power conversion efficiency for over 1000 h at 85 °C.
ISSN:0935-9648
1521-4095
DOI:10.1002/adma.202007431