Synthesis of and its application as a building block for the synthesis of new dimeric and trimeric materials

• Published in: Molecular systems design & engineering 2022-08, Vol.7 (8), p.899-95
• Main Authors: Cariello, Michele, Pant, Namrata, Harkiss, Alexander H, Tracey, Frances M, Cameron, Joseph, Skabara, Peter J, Holliman, Peter J, Docampo, Pablo, Cooke, Graeme
• Format: Article
• ISSN: 2058-9689
• DOI: 10.1039/d2me00038e

Spiro-OMeTAD has become a ubiquitous hole-transporting material (HTM) in perovskite-based solar cells. However, it has several intrinsic drawbacks including its long-term stability, low conductivity and hole-mobility. Hence, the synthesis of new derivatives with improved charge transporting properties remains an important goal. Here, we have devised a novel synthetic route to prepare unsymmetrically functionalised Spiro-OMeTAD derivatives. We report the synthesis of a mono-demethylated Spiro-OMeTAD derivative, SOT-OH , utilising two different synthetic protocols and show two new derivatives, a dimer ( SOT-D ) and a trimer ( SOT-T ) as exemplars. We fully characterise the developed materials and show significantly higher conductivity values than Spiro-OMeTAD when doped with standard ionic salts at the same concentrations. The solar cells fabricated using the mixed composition Cs 0.05 (FA 0.85 MA 0.15 ) 0.95 PbI 3 perovskite and the novel SOT-D show power conversion efficiencies of up to 16.4% under standard AM1.5 illumination compared to 16.1% observed when using the benchmark Spiro-OMeTAD . Dimer and trimer analogues of Spiro-OMeTAD are porous hole transport materials with improved conductivity compared to the parent material and give higher power conversion efficiencies in perovskite solar cells.