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

[ali_b]

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?

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


beam num=1 f.radiate=solarex07.lib

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