Dear John,

welcome,

The open circuit voltage is related to the energy gap of the active material of the solar cells which absorbs part of the incident solar radiation. As the energy gap increases the open circuit voltage increases. So, the relatively high open circuit voltage is because the Die has a relatively high energy gap.

Since the die is organic semiconductor its absorption thickness is equal to the exciton length which is about 20-30 nm. In order to absorb most of the incident radiation the required thickness is about 200:400 nm. This is achieved by filling the bores of a scaffold electron transport material TiO2 by the Die. and thereby thickening the optical path in the Die.

It is so that as the band gap increases the Die will absorb only a part of the incident solar spectrum with photo energy higher than the energy gap which leads to the reduction of the photcurrent. In addition not all the incident photons will lead to collection of electrons and holes because of the recombination losses. The external quantum efficeincy depends on how optimum the solar cell is constructed.

Best wishes

John,

The short-circuit current is the product of the collection of the generated charge carriers, and therefore, depends on a series of factors that I enunciate below:

1.- The area of ​​the solar cell, for this reason, and for comparison purposes, this parameter of the cell is generalized by defining the short-circuit current density, commonly expressed as "Jsc", and expressed in mA/cm2 units.

2.- The number of incident photons, that is, the power of the incident radiation source, for the measurement of the solar cells, a standard of power density known as AM1.5 equivalent to 100 mW/cm2 is used. Therefore there is nothing left to do in this way since your source of final illumination would be the sun.

3.- The spectrum of the incident light and the espectral response of the solar cell. The higher the spectral response, more current the solar cell can generate, as long as the incident spectrum is of equal or greater width in wavelengths.

4.- Of the optical properties (absorption and reflection) of the solar cell.

5.- Of the probability of charge generation, which depends mainly on the passivation of the surface of the absorber and the life time of the minority carriers in the base.

6.- And finally, of the series resistance values ​​(Rs) associated with the contacts in your cell. High values ​​of Rs would have a direct effect on the efficiency of the cell, causing a decrease in energy conversion due to an increase in heat losses due to the Joule effect. Acceptable values ​​for the Rs of a solar cell revolve around 0.5 Ωcm2.

Thank You Dr. Abdelhalim Zekry and Dr. J.R. Gonzalez to sharing the valuable suggestion.