Equivalent circuit for AC response of Cu(In,Ga)Se2 thin film solar cells

Abstract

Ultrathin Cu(In,Ga)Se2 (CIGS) is desired to reduce production costs of CIGS solar cells. The present work aims to study the AC electrical response of standard-thick, ultrathin and passivated ultrathin devices. Admittance measurements allow to choose the AC equivalent circuit for each type of CIGS device. It is of utmost importance to understand the AC electrical behavior of each device, as the differences between reference thick, reference ultrathin and passivated ultrathin CIGS solar cells are yet to be fully understood. The analyses show a simpler AC equivalent circuit for the reference ultrathin device, which is explained by the lowered bulk recombination for thin film CIGS solar cells when compared with thick ones. The importance of shunts mitigation by the use of a passivation layer is also demonstrated, with a shunt resistance increase for the passivation device compared to both reference devices.