Photocurrent maximum energy conversion efficiency

The multiple band gap solar to electrical conversion efficiency of 19.2% compares favorably to the maximum 15 to 16% solar to electrical energy conversion efficiency previously reported for single band gap PECs [9, 10]. Small photoelectrochemical efficiency losses can be attributed to polarization losses accumulating at the solution interfaces. Under illumination, a photocurrent density of 13 mA cm seen in Fig. 7 is consistent with polarization... 

A surface of p-InP was modified by the electrodeposition of submonolayer amounts of various metals and the photocurrent vs. potential behavior studied. The photocurrents observed at 0 V vs. NHE for various surface treatments are shown in the Table E.2. Calculate the maximum efficiency of energy conversion in each case and comment on the observed trend. The light source was an Xe lamp and incident light intensity was 50 mW cm-2. (Contractor)... 

Fig. 1.2 Theoretical maximum solar-to-hydrogen (STH) conversion efficiency (left axis) and photocurrent (right axis) as a function of material band gap. The theoretical maximum STH plotted here only considers the first thermodynamic principle of energy conservation and is analogous to the ultimate efficiency for a p-n junction solar cell described by Shockley and Queisser [14]...

Ignoring parasitic resistances, Eq. (8.4) shows that Vqc increases logarithmically with the photocurrent to a maximum value approximately equal to the energy difference between Ehomo(JX) and EeumoW, with corrections for polaron effects [8, 9]. Equation (8.5) would suggest that power conversion would be optimised by designing the molecular structure of the D and A to maximise Vqc- However, Fig. 8.2 shows that there is a trade-off involved. Efficient charge separation at the interface between the D and A requires a minimum offset between their HOMO and LUMO levels defined as... 

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