Fill factor, photoelectrochemical cells

Photoelectrochemical cells with polythiophene film as an active electrode and a lead plate as a counter electrode in Pb (C104) acetonitrile electrolyte has an open circuit voltage of 0.8 V, short circuit current of 2 x 10 4 A cm-2, efficiency coefficient of 0.03%, fill factor of 15% [194]. The absorption and photosensitivity spectra of such a cell are shown in Fig. 24. The small bathochromic shift in the longwave region for photosensitivity may be related to the photogeneration of the charge carriers via surface states. The photosensitivity maximum is close to the maximum solar intensity. The parameters exceed the ones obtained with polyacetylene. 

In addition to yielding information about semiconductor charge-transfer dynamics, the fill factor parameterizes the efficiency with which the photo-electrochemical cell can be expected to convert optical energy to electricity. The practical value of a photoelectrochemical cell is usually evaluated by its maximum conversion efficiency. The energy conversion efficiency is defined as... 

P. Singh, K. Rajeshwar, R. Singh, and J. DuBow, Estimation of series resistance losses and ideal fill factors for photoelectrochemical cells, J. Electrochem. Soc. 128 (1981) 1396-1398. 

A drawback is the lower conductance of non-aqueous solutions entailing lower fill factors. The investigation of non-aqueous electrolyte solutions for applications in photoelectrochemical cells is still in its swaddling cloths. Only few aspects can be discussed. 

Si to cross the window and reach the electrolyte. The p-Si/n-BP heterojunction photoelectrodes produce large and stable photocurrents up to 15 luA/cm when applied in liquid junction solar cells. A maximum short-circuit photocurrent, isc, of 15 mA/cm could be reached with 80 mW/ cm irradiation power. The open-circuit potential, Voc, was about 0.5 V and the fill factor, T, about 0.5. The maximal gained power at 80 mW/cm irradiation power equals (V X = ij (Voc + (sc) = 3.75 mW/cm which yields a conversion effieieney of tungsten-halogen light of 4 to 5%. The characteristics of photoelectrochemical cells have been greatly improved in comparison with those of fluxed BP crystals (75). 

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