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Capturing Mobile Lithium Ions in a Molecular Hole Transporter Enhances the Thermal Stability of Perovskite Solar Cells
Author(s) -
Kim SeulGi,
Le Thi Huong,
Monfreid Thybault,
Goubard Fabrice,
Bui ThanhTuân,
Park NamGyu
Publication year - 2021
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202007431
Subject(s) - materials science , thermal stability , energy conversion efficiency , lithium (medication) , fourier transform infrared spectroscopy , perovskite (structure) , electron mobility , chemical engineering , analytical chemistry (journal) , organic chemistry , optoelectronics , chemistry , medicine , engineering , endocrinology
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 cm 2 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.