Density of interface states, excess capacitance and series resistance in the metal–insulator–semiconductor (MIS) solar cells

Dark and illuminatied current–voltage (I–V) characteristics of Al/SiOx/p-Si metal–insulator–semiconductor (MIS) solar cells were measured at room temperature. In addition to capacitance–voltage (C–V) and conductance–voltage (G–V), characteristics are studied at a wide frequency range of 1 kHz–10 MHz. The dark I–V characteristics showed non-ideal behavior with an ideal factor of 3.2. The density of interface states distribution profiles as a function of (Ess−Ev) deduced from the I–V measurements at room temperature for the MIS solar cells on the order of ≅1013 cm−2 eV−1. These interface states were responsible for the non-ideal behavior of I–V, C–V and G–V characteristics. Frequency dispersion in capacitance for MIS solar cells can be interpreted only in terms of interface states. The interface states can follow the a.c. signal and yield an excess capacitance, which depends on the relaxation time of interface states and the frequency of the a.c. signal. It was observed that the excess capacitance Co caused by an interface state decreases with an increase of frequency. The capacitances characteristics of MIS solar cells are affected not only in interface states but also series resistance. Analysis of this data indicated that the high interface states and series resistance leads to lower values of open-circuit voltage, short-circuit current density, and fill factor. Experimental results show that the location of interface states and series resistance have a significant effect on I–V, C–V and G–V characteristics.