The Importance of Pendant Groups on Triphenylamine‐Based Hole Transport Materials for Obtaining Perovskite Solar Cells with over 20% Efficiency

• Published in: Advanced energy materials 2018, Vol.8 (2), p.n/a
• Main Authors: Zhang, Jinbao, Xu, Bo, Yang, Li, Ruan, Changqing, Wang, Linqin, Liu, Peng, Zhang, Wei, Vlachopoulos, Nick, Kloo, Lars, Boschloo, Gerrit, Sun, Licheng, Hagfeldt, Anders, Johansson, Erik M. J.
• Format: Article
• Language: English
• Subjects: Charge materials; Charge transport; Energy conversion efficiency; Energy levels; Engineering Science with specialization in Nanotechnology and Functional Materials; high efficiency; hole transport materials; Low conductivity; Optoelectronics; Organic chemistry; perovskites; Photovoltaic cells; photovoltaic devices; Solar cells; Teknisk fysik med inriktning mot nanoteknologi och funktionella material; Thin films
• ISSN: 1614-6832; 1614-6840; 1614-6840
• DOI: 10.1002/aenm.201701209

Tremendous progress has recently been achieved in the field of perovskite solar cells (PSCs) as evidenced by impressive power conversion efficiencies (PCEs); but the high PCEs of >20% in PSCs has so far been mostly achieved by using the hole transport material (HTM) spiro‐OMeTAD; however, the relatively low conductivity and high cost of spiro‐OMeTAD significantly limit its potential use in large‐scale applications. In this work, two new organic molecules with spiro[fluorene‐9,9′‐xanthene] (SFX)‐based pendant groups, X26 and X36, have been developed as HTMs. Both X26 and X36 present facile syntheses with high yields. It is found that the introduced SFX pendant groups in triphenylamine‐based molecules show significant influence on the conductivity, energy levels, and thin‐film surface morphology. The use of X26 as HTM in PSCs yields a remarkable PCE of 20.2%. In addition, the X26‐based devices show impressive stability maintaining a high PCE of 18.8% after 5 months of aging in controlled (20%) humidity in the dark. We believe that X26 with high device PCEs of >20% and simple synthesis show a great promise for future application in PSCs, and that it represents a useful design platform for designing new charge transport materials for optoelectronic applications. The importance of the pendant groups on triphenylamine‐based hole transport materials (HTMs) in perovskite solar cells is investigated. A new HTM X26 with optimal spiro[fluorene‐9,9′‐xanthene]‐based pendant groups shows an efficiency of over 20%. This work demonstrates that the pendant groups in HTMs play important roles in determining the molecular property, solar cell performance, and stability.