AUTHOR=Guo Ying 

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

JOURNAL=Frontiers in Chemistry

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.928712

DOI=10.3389/fchem.2022.928712

ISSN=2296-2646

ABSTRACT=Perovskite solar cells (PSCs) have achieved excellent power conversion efficiencies (PCEs), however, there still exist some major challenges on device stability due to the hydrophilic Lithium bis((trifluoromethyl)sulfonyl)azanide (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). While ion migration, corrosiveness and hygroscopicity induced by the additive Li-TFSI is 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 for improving the conductivity of spiro-OMeTAD. As a result, the PSCs with TPP achieved a fill factor (FF) of 0.820 with an enhanced PCE of 23.03%, considerably higher than that of the Li-TFSI-doping device (22.39%) and comparable to Li-TFSI and Co-TFSI co-doped device (23.43%). 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 accelerates interfacial carrier transportation and minimize the open-circuit voltage (Voc) 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 1100 h outputting. Thus, this work will open up new possibilities for hydrophilic Li-TFSI dopant replacements.