Study of bandgap profiling control on photovoltaic performance in the three stacked amorphous solar cells
Y. Nakata, H. Sannomiya, S. Moriukchi, A. Yokata, Y. Inoue, M. Itoh, and H.Itoh,
Mater. Res. Soc. Symp. Proc. 192, 15 (1990).