I am dealing with current problems and solving differential equations.
phi1 [x] was solved using DSolve.
However, I used DSolve to solve phi2 [x] using 4 boundary conditions, but instead of outputting results, It just show my input.
I write the relevant code below(OutPut for phi2 [x] is omitted) and attach the Mathemtica file.
What's wrong?
ClearAll[phi1, phi2]
eqn1 := D[phi1[x], {x, 2}] == -q nd / esi
bc1 := phi1[tch + tox esi/eox] == vg - vfb
bc2 := phi1[-tox esi/eox] == vg - vfb
DSolve[{eqn1, bc1, bc2}, phi1[x], x]
{{phi1[x] -> (
eox esi nd q tch tox + esi^2 nd q tox^2 - 2 eox^2 esi vfb +
2 eox^2 esi vg + eox^2 nd q tch x - eox^2 nd q x^2)/(
2 eox^2 esi)}}
eqn2 := D[phi2[x, y], {x, 2}] + D[phi2[x, y], {y, 2}] == 0
bc3 := phi2[x, 0] == vs - phi1[x]
bc4 := phi2[x, l] == vs + vd - phi1[x]
bc5 := phi2[tch + tox esi/eox, y] == 0
bc6 := phi2[-tox esi/eox, y] == 0
DSolve[{eqn2, bc3, bc4, bc5, bc6}, phi2[x, y], {x, y}]
Attachments: