• Energy and Wavelength, both are as x-axis.
• data start from 5th line. 

DNTT_C60_KCl.csv

set terminal wxt font ',13'

set datafile separator ";"

unset label
set label

set xrange [180:1000]
set yrange [0:]

set xlabel ' Wavelength [nm]'

set x2tics
set xtics nomirror
set link x2 via 1240/x inverse 1240/x
set x2label 'Evergy [eV]'

set label '3.5eV' at 350.630, 0.142387 offset -1,1
set label '2.7eV' at 448.347, 0.173382 offset -1,1

plot \
'DNTT_C60_KCl.csv' every ::5 u 1:($2+0.21) w line title 'DNTT',\
'DNTT_C60_KCl.csv' every ::5 u 1:($3/3+0.02) w line title 'C60 intensity /3'