The $\mathrm{P}-\mathrm{N}$ junction will conduct only when it is forward biased i.e. when $-5 \mathrm{V}$ is fed to it, so it will conduct only for third quarter part of signal shown and when it conducts potential drop $5 \mathrm{V}$ will be across both the resistors, so output voltage across ${\mathrm{R}}_2$ is $2.5 \mathrm{V}$.

$\therefore {\text{V}}_0=-2.5\text{V}$