Doped but Stable: Spirobisacridine Hole Transporting Materials for Hysteresis-Free and Stable Perovskite Solar Cells

Drigo, N, Roldan-Carmona, C, Franckevičius, M ORCID: https://orcid.org/0000-0001-8020-7201, Lin, KH, Gegevičius, R, Kim, H ORCID: https://orcid.org/0000-0002-5296-8975, Schouwink, PA, Sutanto, AA ORCID: https://orcid.org/0000-0002-9413-2789, Olthof, S ORCID: https://orcid.org/0000-0002-8871-1549, Sohail, M ORCID: https://orcid.org/0000-0002-8221-818X, Meerholz, K, Gulbinas, V, Corminboeuf, C ORCID: https://orcid.org/0000-0001-7993-2879, Paek, S ORCID: https://orcid.org/0000-0002-2671-2909 and Nazeeruddin, MK ORCID: https://orcid.org/0000-0001-5955-4786 (2020) Doped but Stable: Spirobisacridine Hole Transporting Materials for Hysteresis-Free and Stable Perovskite Solar Cells. Journal of the American Chemical Society, 142 (4). pp. 1792-1800. ISSN 0002-7863

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Abstract

Four spirobisacridine (SBA) hole-transporting materials were synthesized and employed in perovskite solar cells (PSCs). The molecules bear electronically inert alkyl chains of different length and bulkiness, attached to in-plane N atoms of nearly orthogonal spiro-connected acridines. Di-p-methoxyphenylamine (DMPA) substituents tailored to the central SBA-platform define electronic properties of the materials mimicking the structure of the benchmark 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene (spiro-MeOTAD), while the alkyl pending groups affect molecular packing in thin films and affect the long-term performance of PSCs. Devices with SBA-based hole transporting layers (HTL) attain efficiencies on par with spiro-MeOTAD. More importantly, solar cells with the new HTMs are hysteresis-free and demonstrate good operational stability, despite being doped as spiro-MeOTAD. The best performing MeSBA-DMPA retained 88% of the initial efficiency after a 1000 h aging test under constant illumination. The results clearly demonstrate that SBA-based compounds are potent candidates for a design of new HTMs for PSCs with improved longevity.