Origin of apparent light-enhanced and negative capacitance in perovskite solar cells

So-called negative capacitance seems to remain an obscure feature in the analysis of the frequency-dependent impedance of perovskite solar cells. It belongs to one of the puzzling peculiarities arising from the mixed ionic-electronic conductivity of this class of semiconductor. Here we show that apparently high capacitances in general (positive and negative) are not related to any capacitive feature in the sense of a corresponding charge accumulation. Instead, they are a natural consequence of slow transients mainly in forward current of the diode upon ion displacement when changing voltage. The transient current leads to a positive or negative 'capacitance' dependent on the sign of its gradient. The 'capacitance' appears so large because the associated resistance, when thinking of a resistor-capacitor element, results from another physical process, namely modified electronic charge injection and transport. Observable for a variety of devices, it is a rather universal phenomenon related to the hysteresis in the current-voltage curve.


Published in:
Nature Communications, 10, 1574
Year:
Apr 05 2019
Publisher:
London, NATURE PUBLISHING GROUP
ISSN:
2041-1723
Keywords:
Laboratories:




 Record created 2019-06-18, last modified 2019-06-25


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