A new figure of merit for qualifying the fluorine-doped tin oxide glass used in dye-sensitized solar cells

We have successfully obtained a new figure of merit for qualifying fluorine-doped tin oxide (FTO) glass in dye-sensitized solar cells (DSCs) through two equivalent testing methods. These methods are demonstrated and applied to change the equivalent transmittance and sheet resistance of FTO glass even after the glass is assembled in DSCs. By recording the I-V characteristic of a DSC with changed equivalent transmittance and sheet resistance of FTO glass, the dependent relations between the DSC performance (short circuit current density, open circuit voltage, and fill factor) and FTO properties (transmittance and sheet resistance) are found. With these relations, the new figure of merit M(TC) for FTO glass is successfully defined to be in linearly increasing dependence on the efficiency of DSCs. A series of DSCs with different FTO glasses is prepared to test the effectiveness of M(TC) and Haacke's figure of merit Phi(TC), which has been widely used for more than 30 years. The result shows that M(TC) is proportional to the efficiency of DSCs, while Phi(TC) is not. M(TC) could be very useful as a guideline to greatly simplify the process of optimizing the FTO glass to improve the efficiency of DSCs. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3278518]