A Novel Organic Dopant for Spiro-OMeTAD in High-Efficiency and Stable Perovskite Solar Cells

• Published in: Frontiers in chemistry Vol. 10; p. 928712
• Main Author: Guo, Ying
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 25-07-2022
• Subjects: Chemistry; device performance; hole-transporting materials; hydrophobic; operational stability; organic dopants; perovskite solar cells; organic dopants; hole-transporting materials; device performance; hydrophobic; perovskite solar cells; operational stability
• ISSN: 2296-2646; 2296-2646
• DOI: 10.3389/fchem.2022.928712

Perovskite solar cells (PSCs) have achieved excellent power conversion efficiencies (PCEs); however, there still exist some major challenges on device stability due to hydrophilic bis(trifluoromethane)sulfonimide lithium (Li-TFSI), which is commonly introduced as a p-dopant to increase the hole mobility and conductivity of 2,2',7,7'-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) hole-transporting materials (HTMs). Ion migration, corrosiveness, and hygroscopicity induced by the additive Li-TFSI are detrimental to the device stability, which significantly hinders further commercialization of PSCs. Herein, a hydrophobic organic ionic compound, trityltetra(pentafluorophenyl)borate (TPP), is explored as a novel efficient and stable alternative p-dopant, avoiding the long-term aging process to improve the conductivity of spiro-OMeTAD. As a result, the champion efficiency of TPP-based devices delivers performance up to 23.03%, which is higher than that of the Li-TFSI-based devices (22.39%). In addition, the TPP-based devices also exhibit higher average PCE values. The excellent performance with TPP may be associated with the higher work function of doped spiro-OMeTAD and a better alignment of energy levels with the valence band of perovskite, which substantially accelerate interfacial carrier transportation and minimize the open-circuit voltage (
) loss of PSCs. More importantly, the un-encapsulated TPP-doped devices also display much superior operational stability under maximum power point (MPP) tracking with continuous light illumination in an ambient humid environment, which maintained 96-97% of the initial PCE over 1,100 h outputting. Thus, this work will open up new possibilities for hydrophilic Li-TFSI dopant replacements.