I am depositing LiF(1.5 nm) as electron transporting layer in POlymer solar cell (P3HT:PCBM as active layer). I want to know what is the effect of higher thickness of LiF in polymer solar cell(ITO/PDOT:PSS/P3HT:PCBM/LiF/Al).
IIRC, the best thickness of LiF in our lab was a bit below 1 nm, when we were still using LiF... The absolute accuracy is not high in this measurements, I'd suggest to make your own study of optimal LiF thickness... LiF is insulator, so excess thickness greatly increases serial resistance.
Yes, ~0.8 nm is the best. At ~2 nm devices hardly work.
I would also recommend annealing of the blend before LiF-Al deposition. If you anneal devices with LiF-Al, you will loose quite some performance due to the lithium diffusion.
Bare Al typically gives better electrodes than LiF-Al. Ca-Ag cathode would be the optimum.