Comparison of D.C. and A.C. electro-analytical methods for measuring diode ideality factors and series resistances of silicon solar cells

Comparison of D.C. and A.C. electro-analytical methods for measuring diode ideality factors and series resistances of silicon solar cells

The diode ideality factor (m) and the series resistance (Rs) of a Si solar cell represent two criticalperformance-indicator parameters of the device. Since both m and Rs are functions of voltage (V) andtemperature (T), simultaneous electrical measurements of these parameters under variable conditions ofV and T can often be difficult with traditional direct current (D.C.) techniques. Using the electro-analyticalmethod of linear sweep voltammetry (LSV) and a commonly available Si solar cell, we explore thesespecific confines of such D.C. measurements. The results are compared with those obtained from aparallel set of alternating current (A.C.) measurements using impedance spectroscopy (IS). LSV providesthe main D.C. parameters (open circuit voltage, short circuit current, fill factor, and efficiency) of the cell,but is limited in terms of independently measuring m and Rs beyond strong forward biased conditions. The IS approach is free of the latter experimental constraints, and at the same time can provide severalother important electrical parameters of the solar cell. Specifically, IS detects the presence of a low-high(pepþ) junction at the back surface of the cell, and serves as an efficient probe of certain electricalcharacteristics of this junction.

The diode ideality factor (m) and the series resistance (Rs) of a Si solar cell represent two criticalperformance-indicator parameters of the device. Since both m and Rs are functions of voltage (V) andtemperature (T), simultaneous electrical measurements of these parameters under variable conditions ofV and T can often be difficult with traditional direct current (D.C.) techniques. Using the electro-analyticalmethod of linear sweep voltammetry (LSV) and a commonly available Si solar cell, we explore thesespecific confines of such D.C. measurements. The results are compared with those obtained from aparallel set of alternating current (A.C.) measurements using impedance spectroscopy (IS). LSV providesthe main D.C. parameters (open circuit voltage, short circuit current, fill factor, and efficiency) of the cell,but is limited in terms of independently measuring m and Rs beyond strong forward biased conditions. The IS approach is free of the latter experimental constraints, and at the same time can provide severalother important electrical parameters of the solar cell. Specifically, IS detects the presence of a low-high(pepþ) junction at the back surface of the cell, and serves as an efficient probe of certain electricalcharacteristics of this junction.