The effect of p-layers deposited under varying conditions on hydrogenated amorphous silicon p-i-n homojunction solar cell performance

Abstract

Substrate temperature and doping gas ratios are used to vary the boron and hydrogen content of p-iype hydrogenated amorphous silicon (a-Si:H). The effects of the doping gas ratio (B2H6:SiH4) and substrate temperature have been studied and conditions were used such as to give oplical gaps and dark conductivity activation energies which changed by as much as 0.3 eV while the difference between them remained unchanged. The effects of changes in the absorption coefficient and activation energy on p-i-n solar cell device characteristics are quantified by comparing the measured thin film properties with the collection efficiencies and dark and light current-voltage characteristics.

Material Requirements for Buffer Layers Used to Obtain Solar Cells with High Open Circuit Voltages

“…The first observation relates to doping of the emitter a-Si:H p/i/n cell. Dawson et al [2] reported that cells made with the least doped (lower conductivity activation energy) a-Si:H p-layers exhibit highest voltages. It is noteworthy that the introduction of carbon alloying for the p layer, which usually makes it easier to obtain high V OC , has the tendency to reduce the electron mobility and introduces a barrier for electron back diffusion.…”

Wide bandgap p-type window layer prepared by trimethylboron doping at high temperature for a-Si:H superstrate solar cell

“…And the H content also decreased. Dawson et al observed the decrease of the optical bandgap and the improvement of dark conductivity, which was attributed to the decrease of the boron activation energy by the authors [25]. Pruppers et al also presented the gradually decreased H content.…”