Silicon heterojunction solar cells with p nanocrystalline thin emitter on monocrystalline substrate

Heterojunction solar cells with n-type nanocrystalline silicon emitters on p-type c-Si wafers

“…Ensuring formation of a certain value fraction of nanocrystllites in the 15 nm n-layer, a hydrogen plasma treatment for the underlying a-Si:H i-layer surface was used to enhance the formation of nucleation sites, as employed in other laboratories [16], because there is a possible barrier for nanocrystalline nucleation on an amorphous i-layer surface [17]. Upon these improvements, the performance of the solar cells was largely enhanced.…”

Silicon heterojunction solar cells with microcrystalline emitter

“…1) the continuity of the a-Si:H layer is maintained after emitter deposition. As a consequence, the V oc is independent of i-layer thickness, with extremely limited spread, confirming that the passivation properties of such layers [6] are preserved after lc deposition, with no degradation of the film continuity nor plasma-induced crystallization [3]. However, due to the more favorable band discontinuity configuration [7], we obtained much larger V oc values for p/n devices, having m/a structure, if a much thicker a-Si:H layer is used [2,3,6], the more convenient approach being still an open point.…”

“…[3] we have shown the partial crystallization suffered by a 5 nm thick a-Si:H layer, if exposed to a VHF highly hydrogen diluted plasma, used to deposit the p-type lc emitter of p/n devices [5]. However, the fabrication of n-type lc emitters requires less stringent deposition conditions.…”

“…The lc fraction was obtained by simulating the UVvisible (190-820 nm) reflectance spectra. The simulation makes use of the Bruggemann effective medium approximation and a multilayer model based on Fresnel formulation [3]. The fit parameters were the layer thicknesses, and the lc, a-Si:H and void volume fractions.…”

“…However, in case of VHF deposition of p-type lc-Si, significant interaction with the underlying a-Si:H buffer layer is known to occur because of the long range effect of hydrogen on silicon [3].…”