Specific features of current flow in $\alpha$-Si : H/Sii heterojunction solar cells

Specific features of the formation of dark I–V characteristics of $\alpha$-Si : H/Si heterojunction solar cells are investigated taking account the ratio between silicon doping level $N_d$ and excess concentration $\Delta_n$ of electron–hole pairs. It is demonstrated that, at $\Delta_n\ge N_d$, the I–V characteristic is fundamentally different from the characteristic of a classical Shockley diode due the effect of the backside surface (additional drop of the applied voltage). The results of analysis are used to describe the experimental I–V characteristics reported in studies on $\alpha$-Si : H/Si heterojunction solar cells. Numerical values of the ideality factors of the dark I–V characteristics are obtained by comparing the experimental and calculated curves.