# Convergence problem in using pasveer mobility model for organic solar cell in silvaco

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#### ali_b

##### Newbie level 1
i am trying to simulate an OSC including Extended Gaussian
Disorder Model (or equivalently pasveer mobility model) in silvaco, but the solution doesn't converge (it had this warnings and errors: "Error string found in output", "Newton algorithm did not converge in 5 iterations.","Bias step cut back more than 4 times. Cannot trap."). i tried to solve the problem by changing different parameters such as iteration limit, tolerances ,... but it didn't converge. i have attached my code. Could anyone advise on this convergence problem?
Code:
go atlas

set sighat=4
set k=1.3806488e-23
set q=1.602176565e-19
set tl=300
set Nt=8.51e20
set a=1e7/pow(${Nt},0.3333333333) set sig=${sighat}*${k}*${tl}/${q} set organic_thick=0.12 set ITO_thick=0.03 set Cathode_thick=0.06 set total_thick=$organic_thick + $Cathode_thick ############ # MESH ############ mesh smooth=1 space.mult=1.0 x.mesh l= 0.0 spacing=0.01 x.mesh l=0.3 spacing=0.01 y.mesh l=-$ITO_thick    spacing=0.01
y.mesh l=0.0            spacing=0.01
y.mesh l=$organic_thick spacing=0.01 y.mesh l=$total_thick spacing=0.01

############
# REGION
############

region num=1   material=PPV    x.min=0 x.max=0.3 y.min=0 y.max=$organic_thick ############ # ELECTRODE ############ electrode num=1 name=anode x.min=0 x.max=0.3 y.min=-$ITO_thick \
y.max=0 material=ITO
electrode   num=2  name=cathode x.min=0 x.max=0.3 y.min=$organic_thick \ y.max=$total_thick material=Aluminum

############
# MATERIAL
############

material mat=PPV affinity=3.8 eg300=1.34 nc300=2.5e19 nv300=2.5e19 permi=3.4 \
qe.exc=1 knrs.exciton=1.82694e6 rst.exc=1 lds.exc=0.01 taus.exc=1e20 s.binding=0.28484 a.singlet=1.32167 ntc.gauss=$Nt sigc.gauss=$sig

############
# MODEL
############

mobility material=PPV mun0=2.5e-3 mup0=3.0e-4 pasveer.n pasveer.p

models langevin singlet s.dissoc

############
# CONTACT
############

contact num=2 workf=3.7
contact num=1 workf=5.0

method itlimit=250 ls.damping lsd.skip.iter=3 weak=1 xnorm

solve init

solve b1=1.0

log outf=solarex3.log
solve vanode=0.0 vstep=0.02   vfinal=0.9 name=anode

tonyplot solarex3.log

quit

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