Investigation of Front-Side Metallization Contact for Screen-Printable Industrial N-TOPCon Solar Cells with Laser-Enhanced Contact Optimization (LECO) Process

N-type TOPCon Solar cells with Laser-Enhanced Contact Optimization (LECO) Process has become an important role in photovoltaic cell technology. During transition from non-LECO process to with-LECO process, front side silver paste for TOPCon cells has been going through major changes. Additive of metallic aluminum has been eliminated, and glass amount has been greatly reduced. In this study, front-side metallization pastes comprising silver, with specific LECO inorganic glass frit, with or without metallic aluminum addition, were designed to contact p+ boron-diffused Si emitter surfaces with SiNx:H-Al2O3 stack antireflection-passivation layers of n-TOPCon-LECO cells. A comparison with conventional Ag-Al paste without LECO process was also performed. Current-Voltage (I-V) measurements, electroluminescence (EL) measurements, transfer length method (TLM) measurements, microtopography of the contacts are characterized. The front-side contact region showing most of anti-reflection coating (ARC) layers has remained, consistent with the current-fired contacts (CFCs) model [1] literature reported. Our results confirms that glass frit for LECO paste must be specifically designed, and that the inclusion of aluminum is not necessarily required. For an optimized LECO frit, in contrast, the addition of of Al may deteriorate device performance due to its potential to damage the emitter and PN-junction.