十八烷基三甲氧基硅烷在低温银包铜浆料中作用的机理分析

Mechanism Analysis on Role of Octadecyltrimethoxysilane in Low-temperature Silver-coated Copper Paste

摘要:

本文采用十八烷基三甲氧基硅烷（ODTMS：Octadecyltrimethoxysilane）作为太阳电池用银包铜浆料的有机包覆剂，系统研究了包覆剂对银包铜粉的抗氧化性、浆料的丝印电极形貌及相关太阳电池性能的影响规律，并分析了包覆剂的作用机理。结果表明，ODTMS可使银包铜粉的疏水性增强，氧化起始温度从250.00℃提高到297.33℃。400℃的氧化增重从3.48%降低至0.91%；适量的ODTMS可以改善银包铜粉体的分散性及浆料中树脂的分布状态，使浆料固化后形成的银包铜电极的体电阻率和接触电阻率都有所降低，并使太阳电池的开路电压略微增大，最终，ODTMS使用量为0.04%时SHJ太阳电池获得最高转换效率，并低于粉体表面能最低值（0.12%）。当ODTMS使用量≥0.08%，银包铜粉表面形成Si-O-Si网络造成电极导电性逐渐变差，电池的开路电压和填充因子逐渐降低。

Abstract:

Surface organic coating represents a pivotal technology for enhancing the performance of silver-coated copper (Cu@Ag) powder and its corresponding paste. However, the adsorption behavior of coating agents on the powder surface and their underlying mechanisms governing the properties of the powder, paste, and the overall performance of solar cells remain to be systematically investigated. In this study, octadecyltrimethoxysilane (ODTMS) was employed as the coating agent for Cu@Ag powder, with varying dosages of ODTMS used to fabricate Cu@Ag pastes. The application efficacy and action mechanisms were explored using silicon heterojunction (SHJ) solar cells as a model system. The results indicate that ODTMS treatment enhances the hydrophobicity of Ag-Cu powder, elevating its oxidation onset temperature from 250.00°C to 297.33°C. An optimal dosage of ODTMS improves powder dispersibility and resin distribution, leading to reduced bulk resistivity and contact resistivity of the cured metal electrodes on the cells, as well as a slight increase in the open-circuit voltage (VOC) of the devices. When the ODTMS dosage reaches or exceeds 0.08%, the formation of a Si-O-Si network on the Cu@Ag powder surface progressively degrades the electrical conductivity of the electrodes, moreover, a gradual decrease is also manifested in VOC and fill factor(FF) of the SHJ cells. The printed line width of ODTMS-treated samples is marginally larger than that of untreated sample, but the difference is negligible among the treated samples, resulting in no significant variation in short-circuit current density (JSC). Ultimately, the SHJ solar cells achieve the highest conversion efficiency when the ODTMS dosage is 0.04%.