High\nEfficiency Inverted Organic Solar Cells with\na Neutral Fulleropyrrolidine Electron-Collecting Interlayer

Abstract

A novel\nfulleropyrrolidine derivative, named FPNOH, was designed,\nsynthesized, and utilized as an efficient electron-collecting (EC)\nlayer for inverted organic solar cells (i-OSCs). The grafted diethanolamino-polar\nmoieties can not only trigger its function as an EC interlayer, but\nalso induce orthogonal solubility that guarantees subsequent multilayer\nprocessing without interfacial mixing. A higher power conversion efficiency\n(PCE) value of 8.34% was achieved for i-OSC devices with ITO/FPNOH\nEC electrode, compared to that of the sol–gel ZnO based reference\ndevices with an optimized PCE value of 7.92%. High efficiency exceeding\n7.7% was still achieved even for the devices with a relatively thick\nFPNOH film (16.9 nm). It is worthwhile to mention that this kind of\nmaterial exhibits less thickness dependent performance, in contrast\nto widely utilized p-type conjugated polyelectrolytes (CPEs) as well\nas the nonconjugated polyelectrolytes (NCPEs). Further investigation\non illuminating intensity dependent parameters revealed the role of\nFPNOH in reducing interfacial trap-induced recombination at the ITO/active\nlayer interface.