Analysis of a-Si:H/TCO contact resistance for the Si heterojunction back-contact solar cell

Back-Contacted Silicon Heterojunction Solar Cells With Efficiency >21%

“…This is on par with the best published back-contacted SHJ devices [10], [11], [35], excluding the outstanding results of Panasonic [8] and Sharp [9], of which precise details about the fabrication complexity are undisclosed.…”

“…Similarly, another impressive result was recently reported by Sharp, Japan; its so-called rear heterojunction emitter plus antireflective passivation layers concept, using interdigitated back contacts, yielded a conversion efficiency of 24.7%, on a cell area <4 cm 2 [9]. Furthermore, a conversion efficiency of 20.5%, on a cell area of 221 cm 2 , was reached by LG, Korea [10], again by means of an interdigitated back-contacted silicon heterojunction (IBC-SHJ) device. Always in the field of IBC-SHJ devices, Helmholtz-Zentrum Berlin, Germany, has reported a conversion efficiency of 20.2% [11], whereas several other groups have presented solar cells with conversion efficiencies in the range of 15-20% [12]- [15].…”

“…We find that transport losses at the heterocontacts have a preponderant role in the determination of the total device R N series and the associated ΔFF_R series In a range of specific contact resistivity values 0.1-0.5 Ω·cm 2 , for both emitter ((ρ c ) p ) and base ((ρ c ) n ) heterocontacts, the FF loss associated with only the contact resistance component goes from a minimum of 2.7% absolute to a value of 13.8% absolute, which are indeed significant losses. The range 0.1-0.5 Ω·cm 2 covers most of the values reported in the literature for the specific contact resistivity of the heterocontacts [10], [41], [42]. On the other hand, the FF loss associated with lateral conduction in the base accounts for 1.6% absolute, and the overall FF loss associated with the different grid resistance components is 1.7% absolute.…”

“…FF losses associated with heterocontact transport properties can be at least partially ascribed to the TCO/a-Si:H interface [10], [43]- [46]. Our experimental work with IBC-SHJ confirms the importance of this interface with respect to series-resistance losses; changes in the TCO layer composition have shown a relevant impact on total series resistance and FF of final devices (data not shown), as have changes in the deposition conditions of the doped a-Si:H layers.…”

Back-Contacted Silicon Heterojunction Solar Cells: Optical-Loss Analysis and Mitigation

“…First and foremost, two front-side schemes are predominantly featured in such devices: either a-Si:H layers combined with dielectrics-based ARCs [14], [17], [19]- [22] or high-temperature diffused front-surface fields (FSF) combined with ARCs [15], [23]. These two options originate from stacks standardly used in two-side contacted solar cells, usually featured at the front side of both heterojunction [24] and homojunction [25] rear-emitter devices, respectively.…”