A kind of low recombination firing-through screen-printing aluminum (Al) paste is proposed in this work to be used for a boron-diffused N-type solar cell front side metallization. A front side fire-through contact (FTC) approach has been carried out for the formation of local contacts for a front surface passivated solar cell. With a low contact resistivity (ρc) of 1.0 mΩ·cm2, good ohmic contact between the boron-doped front surface of the silicon sample and the Al paste was realized. To obtain a good energy conversion efficiency, a balance can be achieved between the open circuit voltage (Voc) and contact resistivity (ρc) of the cell by combining suitable Al powders and appropriate additives. The detailed micro-contact difference in Si/metallization between the firing-through Al paste and silver-aluminum (Ag-Al) paste was analyzed. The dark saturation current density beneath the metal contact (J0, metal) of the Si/metallization region using our firing-through Al paste was discussed, which was proven to be 61% lower than using Ag-Al paste. The pseudo energy conversion efficiency of the cell using Al paste measured by Suns-VOC was also higher than using Ag-Al paste. The role of Al paste in low surface metal recombination is discussed. The utilization of this new kind of Al paste was much cheaper and more convenient, compared to the traditional process using Ag or Ag-Al paste.

Recently, the efficiency of CdTe thin film solar cell has been improved by using new type of window layer Mg x Zn1−x O (MZO). However, it is hard to achieve such a high efficiency as expected. In this report a comparative study is carried out between the MZO/CdTe and CdS/CdTe solar cells to investigate the factors affecting the device performance of MZO/CdTe solar cells. The efficiency loss quantified by voltage-dependent photocurrent collection efficiency (η C(V′)) is 3.89% for MZO/CdTe and 1.53% for CdS/CdTe solar cells. The higher efficiency loss for the MZO/CdTe solar cell is induced by more severe carrier recombination at the MZO/CdTe p–n junction interface and in CdTe bulk region than that for the CdS/CdTe solar cell. Activation energy (E a) of the reverse saturation current of the MZO/CdTe and CdS/CdTe solar cells are found to be 1.08 eV and 1.36 eV, respectively. These values indicate that for the CdS/CdTe solar cell the carrier recombination is dominated by bulk Shockley–Read–Hall (SRH) recombination and for the MZO/CdTe solar cell the carrier recombination is dominated by the p–n junction interface recombination. It is found that the tunneling-enhanced interface recombination is also involved in carrier recombination in the MZO/CdTe solar cell. This work demonstrates the poor device performance of the MZO/CdTe solar cell is induced by more severe interface and bulk recombination than that of the CdS/CdTe solar cell.

Efficient carrier transport and suppressed interface recombination at back contact are essential for high-efficiency solar cells. Herein, we developed a zirconium nitride (ZrN) film with a low film resistivity of 1.6 × 10−4 Ω cm as an electron-selective contact for n-type silicon solar cells. Suitable band alignment of the n-Si/ZrN hetero-contact eliminates the interface barrier between Al and n-Si. Meanwhile, electrostatic potential induced by interfacial Si–O–Zr bonds assists electron extraction. The fill factor of devices has been significantly improved by incorporating a ZrN layer. After optimizing the thickness of ZrN and contact fraction, the champion ZrN-based device exhibited an efficiency of 19.7%, yielding a 23% enhancement compared with that without a ZrN interlayer.