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Abstract 2,2′,7,7′‐tetrakis‐(N,N‐di‐4‐methoxyphenylamino)‐9,9′‐spirobifluorene (spiro‐MeOTAD) hole transport material (HTM) is a milestone in the history of perovskite solar cells (PSCs). Proper choice of HTMs is key factor for efficient charge extraction and stability in solar cells. Spiro‐MeOTAD is proven to be the most suitable HTM for testing PSCs due to its facile implementation and high performance. Similarly, spiro‐MeOTAD is receiving attention in other applications other than in solar cells due to its desirable properties. However, spiro‐MeOTAD is under debate regarding the topics of cost‐performance, long‐term stability, degradation issues (induced by temperature, additives, film quality, and environmental conditions), coating technologies compatibility, reliance on additives, and hysteresis. In this review, the advent of spiro‐MeOTAD, and related aforementioned issues about spiro‐MeOTAD are discussed. In addition, spiro‐MeOTAD properties, alternative and new additives, other applications, and new HTMs that is comparable or outperforms spiro‐MeOTAD in PSCs are summarized. In the outlook, the future research directions based on reported results that warrant further investigations are outlined.
Hawash et al. (Wed,) studied this question.