Even though interdigitated back contact (IBC) architecture produces the most efficient solar cells, it is difficult to make them cost-effective and industrially viable. Therefore, single-sided atmospheric pressure chemical vapor deposition (APCVD) is investigated for the fabrication of IBC solar cells because it reduces the overall thermal budget, simplifies wet bench processing, and requires no additional masking layer. For the fabrication of a full APCVD IBC solar cell, a very lightly doped front surface field (FSF) of 650 Ω/sq, a heavier doped back surface field (BSF) of 100 Ω/sq and a moderately doped emitter of 250 Ω/sq was used. The high-temperature annealing step is partially done in an oxygen (O₂) environment to (i) drive in dopants, (ii) prevent the formation of a boron-rich layer in case of p⁺ doped c-Si, and (iii) grow an in-situ SiO₂ at the Si/dopant glass interface. The etch rate difference between the in-situ grown SiO₂ and the doped glass layer is utilized to etch the doped glass completely. The retained in-situ SiO₂ after etching is capped with plasma-enhanced chemical vapor deposited (PECVD) SiN_x for the passivation of both polarities of IBC solar cells. A full APCVD IBC solar cell precursors (i.e. before metallization) obtained implied open-circuit voltage (iV_oc) of 714 mV and emitter saturation current density (J_0s) of 17 fA/cm². At the device level, a full APCVD IBC solar cell achieved a conversion efficiency of 22.8% with V_oc of 696 mV and short-circuit current density J_SC of 41.3 mA/cm². These parameters are comparable to the commercially available full-tube diffused ZEBRA® IBC solar cells.

In this work, we developed an in situ annealing process to crystallize boron-doped amorphous silicon [a-Si(p+)] layers deposited by atmospheric pressure chemical vapour deposition (APCVD) to form boron-doped polycrystalline silicon [poly-Si(p+)] layers. The influence of the temperature profiles during a-Si(p+) inline deposition on structural, electrical, and passivation properties was studied in detail. The results show that a-Si(p+) layers can be successfully crystallized by fine-tuning the temperature profiles in the postdeposition zones of the APCVD tool. It was observed that the hydrogenation processes during the fast firing play a significant role in enhancing the passivation quality as well as the electrical properties of the in situ annealed poly-Si(p+) layers. The sheet resistance (Rsh) and implied open circuit voltage (iVoc) of the best in situ annealed poly-Si(p+) layers were found to be comparable to the ones that were ex situ annealed in the tube furnace at 950 $^{\circ }$C for 30 min. The sheet resistance of 200 $\Omega$/$\square$ could be obtained on 150-nm thick poly-Si(p+) layers with an (iVoc) of 718 mV. The use of this novel in situ annealing process to form poly-Si(p+) layers opens a new horizon for a lean process sequence without the additional high-temperature annealing step for fabricating solar cells concepts based on passivating contact.