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.
Good luck!
2 nm is definitely on the high side (if accurately measured), depending on your evaporation machine and measurement conditions you will find the best between 0.6 and 1.5nm. Vladimir is right, best is to make your own study, first round with 0.2nm steps around 1nm (+/-) and second round with 0.1nm around the best position. If your aiming at different materials screening, make sure of the stability of your evaporation process. For different polymers, LiF optimal thikness might be slightly different, so to obtain hero device you have to redo the study.
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