Computer modeling of n-ZnO/p-Si single heterojunction bifacial solar Cell

Bifacial solar cell offers the advantage of harvesting the sunlight more effectively and produce extra power from albedo in addition to slightly lower module temperature. Silicon bifacial cells have been studied and commercially produced with doped back surface field (BSF) in conjunction with dielectric passivation. In this study detailed computer modeling of ZnO based bifacial solar cell is performed to critically investigate the potential doped BSF (DBSF)/dielectric passivation and charged passivated BSF (CPBSF). In both structures n-ZnO is employed as the emitter because of its intrinsic n-type conductivity and high transparency. Simulation results show that the bifacial n-ZnO/p-Si solar cells are insensitive to the emitter layer thickness up to 1μm compared to conventional Si solar cell with doped emitter. Furthermore, emitter doping concentration of ZnO in the ZnO/p-Si cell shows stable efficiency up to 10
¹⁹
cm
^-3
and drops rapidly for higher doping concentration. The efficiency of the two structures - DBSF and CPBSF with ZnO emitter are similar for base thickness of 140 μm having low carrier lifetime. However, the CPBSF structure exhibits higher efficiency than the DBSF when the carrier lifetime is high. Also, even higher efficiency is obtained with a charge density of 10
¹²
cm
²
leading to ~15 mV higher V
_oc
than DBSF counterpart.