A new technique for characterizing floating-junction-passivated solar cells from their dark IV curves

The incorporation of a floating junction (FJ) at the surface of a solar cel l is a proven means of attaining excellent surface passivation, The develop ment of FJ passivation for commercial use, however, has been hindered by an inherent difficulty in characterizing the FJ itself; to measure FJ paramet ers directly requires that electrical contact be made to the floating (i.e. uncontacted) layer that farms the FJ, and this is an irreversible process that can alter the properties of the FJ, This paper presents a new, simple technique to characterize an FJ that does not require electrical contact to the floating layer. The Ebers-Moll equivalent circuit is used to derive re lationships between the cell parameters of an FJ-passivated solar cell and the shape of its dark IV curve, With these relationships, lumped one-dimens ional values can be determined for the current gains and the dark saturatio n currents of both the contacted and the floating junction, and the shunt r esistance across the FJ. The technique is verified with device simulation a nd then demonstrated on two experimental FJ-passivated solar cells. Copyrig ht (C) 1999 John Wiley & Sons, Ltd.