Improving the efficiency of solar cells is key to reducing the cost of solar power. Now, scientists have developed a new synergistic metallization strategy for tunnel oxide passivated contact (TOPCon) solar cells. The approach achieved a certified power conversion efficiency (PCE) of 26.31%, among the highest reported for this technology.
The new strategy was developed by Prof. YE Jichun's team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in collaboration with Soochow University, Zhejiang Gonda Electronic Technology Co., Ltd., and JA Solar Technology Co., Ltd. The relevant findings were published in Matter.
Crystalline silicon solar cells currently dominate the photovoltaic industry, with TOPCon technology rapidly capturing market share owing to its cost advantages and manufacturing compatibility. By decoupling surface passivation from electrical contact formation, these devices significantly suppress minority-carrier recombination and maintain low contact resistance.
However, conventional metallization processes for fabricating TOPCon solar cells suffer from a trade-off: high-temperature firing of silver-aluminum pastes ensures good electrical contact but causes severe passivation degradation and widens gridlines, increasing optical loss—both of which limit efficiency improvements.
To overcome this challenge, the researchers developed a synergistic metallization strategy that combines a specially designed aluminum-free silver paste with a customized laser-enhanced contact optimization (LECO) process.
By optimizing the molecular configuration and intermolecular hydrogen-bonding network, the researchers designed a highly thixotropic, low-corrosion aluminum-free silver paste with excellent shape-retention capability after screen printing. The paste enables a high gridline aspect ratio of 55%, thereby reducing optical shading while effectively preserving the passivation layer.
In addition, a single-frequency laser continuously scans the front gridlines under a reverse bias, generating localized Joule heating and high carrier injection to form low-resistance contacts without compromising the passivation layer. This LECO process, made possible by the newly designed paste, confines the contact reaction to discrete sites, thus avoiding the extensive lattice disruption and aluminum-induced alloying damage typical of conventional firing.
This synergistic approach ensures efficient charge extraction while keeping metal-induced recombination losses to a minimum. As a result, the TOPCon devices achieved a high certified PCE of 26.31%. Notably, the enhanced spectral response boosted the short-circuit current density (Jsc) to 41.98 mA/cm2, the highest certified Jsc reported for large-area TOPCon solar cells to date.
According to the researchers, the new approach resolves the intrinsic trade-off between contact resistivity and passivation preservation without compromising manufacturability, providing a practical route toward the industrialization of next-generation high-efficiency photovoltaic technologies.
