posted on 2021-09-09, 12:35authored byWenya Song, Lucija Rakocevic, Raghavendran Thiruvallur Eachambadi, Weiming Qiu, João P. Bastos, Robert Gehlhaar, Yinghuan Kuang, Afshin Hadipour, Tom Aernouts, Jef Poortmans
To guarantee a long lifetime of perovskite-based
photovoltaics,
the selected materials need to survive relatively high-temperature
stress during the solar cell operation. Highly efficient n–i–p
perovskite solar cells (PSCs) often degrade at high operational temperatures
due to morphological instability of the hole transport material 2,2′,7,7′-tetrakis
(N,N-di-p-methoxyphenyl-amine)9,9′-spirobifluorene
(Spiro-OMeTAD). We discovered that the detrimental large-domain spiro-OMeTAD
crystallization is caused by the simultaneous presence of tert-butylpyridine (tBP) additive and gold
(Au) as a capping layer. Based on this discovery and our understanding,
we demonstrated facile strategies that successfully stabilize the
amorphous phase of spiro-OMeTAD film. As a result, the thermal stability
of n–i–p PSCs is largely improved. After the spiro-OMeTAD
films in the PSCs were stressed for 1032 h at 85 °C in the dark
in nitrogen environment, reference PSCs retained only 22% of their
initial average power conversion efficiency (PCE), while the best
target PSCs retained 85% relative average PCE. Our work suggests facile
ways to realize efficient and thermally stable spiro-OMeTAD containing
n–i–p PSCs.