Reverse breakdown voltage setting for the diodes in a solar cell model in SPICE

I want to simulate the reverse breakdown behavior of a two diode model solar cell in SPICE.
The diodes configurations without considering the breakdown voltage are as below:

.model diode d( Is=1.5e-10,  xti=3)
.model diode2 d(Is=1.77e-6, n=2, xti=3)


With the given diodes configurations, I can simulate all characteristics before the breakdown voltage point.
By adding the breakdown voltage point to the diode model, I cannot see the curve in forward bias anymore and it does not work properly.

.model diode d( Is=1.5e-10,  xti=3, vrev=15, BV=15)
.model diode2 d(Is=1.77e-6, n=2, xti=3, vrev=15, BV=15)


In short, when I add the code for reverse breakdown voltage point, my diode does not work properly in forward bias! Please help me with this problem.

So when you included the VREV parameter, you changed your model to use the piecewise linear diode model instead of the usual nonlinear model. Your other parameters (IS, XTI, and BV) are ignored and the piecewise linear model parameters that you didn't specify take their default values.. This could make a substantial change to the operating behavior of the diodes in your model.