Figure 1

Illustration of the reciprocal action of light absorption and subsequent carrier collection, complemented by current injection and light emission. In equilibrium, the short circuit current $\delta J_{\mathit{SC},0}$ induced by photons entering into the solar cell through the surface element $dS$ within the angle $d\Omega$ is counterbalanced by the saturation current $\delta J_{\mathit{em},0}$. This injection current leads to an emission of photons equilibrating the incident photons.Reuse & Permissions

Figure 2

(a) Illustration of the optical interaction between two volume elements $d{A}_{a}d{\mathbf{r}}_a$ and $d{A}_{b}d{\mathbf{r}}_b$. Note that the difference between the spherical angles $d{\Omega }_{ab}$ and $d{\Omega }_{ba}$ is due to the assumed difference of the refractive index in ${\mathbf{r}}_a$ and ${\mathbf{r}}_b$. This change of the refractive index is indicated by the kinks in the optical interaction cones. (b) Interaction between a surface element $dS$ and a volume element $dA\left(\mathbf{r}\right)d\mathbf{r}$. Light is entering or is emitted within the spherical angle $d\Omega ({\mathbf{r}}_S,\mathbf{r})$, whereas $dS$ (located at coordinate ${\mathbf{r}}_S$) is seen from the volume element (located at $\mathbf{r}$) within the angle $d\Omega (\mathbf{r},{\mathbf{r}}_S)$.Reuse & Permissions

Figure 3

A solar cell or LED viewed as a multiprobe device. The inputs and outputs of the electrical terminals and the optical terminals are linked by reciprocity relations.Reuse & Permissions

Figure 4

Semilogarithmic plot of the total current $J_{\mathit{tot}}\left(V\right)$ (dotted line) and the radiative current $J_{\mathit{em}}\left(V\right)$ (full line) as a function of voltage $V$ normalized to $kT∕q$. The radiative current $J_{\mathit{em}}\left(V\right)$ has a slope of unity in this representation. Therefore, the vertical distance (at constant $V$) and the horizontal distance (at constant $J$) between any point of the $J_{\mathit{tot}}\left(V\right)$ and $J_{\mathit{em}}\left(V\right)$ characteristics are equal. Thus, we have at any bias point $-\ln \left({\mathrm{EQE}}_{\mathit{LED}}\right)=\ln [J_{\mathit{tot}}\left(V\right)∕J_{\mathit{em}}\left(V\right)]=q\Delta V_{\mathit{OC}}∕kT$.Reuse & Permissions