ABSTRACT
If the photodiode is biased in the fourth quadrant of its I-V characteristics (Fig. 2b), GI can be collected with negative power dissipation, i.e., the energy of the pump lost to TPA can be harvested. In order to analyze the power generation and efficiency of this photovoltaic process, the contributions of carrier injection and recombination to the total current need to be considered. The minority carrier diffusion terms can be conveniently calculated from the celebrated Shockley equation:
),1( /00 −
+×= kTqV
pn D eL
pD L nD
qhLI (5)
where h and L dimensions are depicted in Fig. 2a and the other parameters have the usual meanings.35 Shockley equation is valid, since photogeneration in the +N and +P doped regions is negligible in the p-in diode. This contrasts the conventional solar cell theory, where photogeneration predominantly occurs in N and P doped regions and a more detailed solution of the minority carrier diffusion equations is required.32
