 Solution

Assume one collected electron per absorbed photon, ideality factor one and $T=298\mathrm{K}$. The question does not specify temperature, so the result should also be understood through its temperature-dependent formula. The photocurrent density isAt open circuit the diode current balances that photocurrent:Using $300\mathrm{K}$ gives approximately $0.600\mathrm{V}$. These are current densities, so no device area is needed. Incomplete collection would replace $J_{\mathrm{ph}}$ by the collected current and reduce this estimate.

Without texturing, more incident photons generally escape by reflection, so the absorbed flux and $J_{\mathrm{ph}}$ decrease. Holding $J_0$ and temperature fixed, the voltage falls logarithmically: if absorption is multiplied by $f<1$ and $J_{\mathrm{ph}}\gg J_0$, then $\Delta V_{\mathrm{oc}}\simeq (k_{B}T/q)\ln f$. A real texture also changes surface area and recombination, so an unchanged $J_0$ is an assumption rather than a guarantee.