Electrical modeling of Cu(In,Ga)Se2 cells with ALD-Zn1−xMgxO buffer layers

Electrical modeling of Cu(In,Ga)Se2 solar cells with Zn1−xMgxO buffer layers is performed. A number of different device models are implemented and tested by comparing simulation results and measurement data. Room temperature light-soaking and dark-light cross-over behavior as well as low-temperature characteristics of these cells are studied. The light-soaking improvements in the solar cell parameters are attributed to an increase in buffer donor density, due to persistent photo conductivity, that counteracts charged acceptors in the absorber-buffer region. Dark-light JV-curve cross-over is explained by deep acceptor defects with small electron capture cross-section, in the buffer. Best correspondence to measurements on ZnO and Zn0.83Mg0.17O cells is obtained with models including absorber-buffer interface acceptor states. No wideband-gap surface defect layer is needed to reproduce measurement data.