JA Solar focuses on three key routes - advancement in cell structure, module design optimization, and advancement in module characterization - in pursuit of excellence in TOPCon product development
The adoption of LECO process in the TOPCon cell metallization process, yielded an efficiency boost of 0.2% to 0.4% which translated into a module power gain of up to 10 W
The half-cell edge passivation technology, featuring an atomic layer deposition (ALD) tool, resulted in a 0.19% efficiency gain, translating into a module-level power output gain of up to 6 W
JA Solar's TOPCon modules, equipped with busbarless (0BB) TOPCon cells, welded with low-temperature electrical conductive adhesive (ECA) stringing technology, saves up to 20% of silver paste compared to traditional SMBB metallization
With a greater emphasis on TOPCon cell technology compared to HJT cell technology, many vertically integrated TOPCon solar module manufacturers are focusing their efforts on enhancing cell technology, advancing module design, and improving performance in their pursuit of excellence.
At the recent TaiyangNews High-Efficiency Solar Technologies 2024 Virtual Conference, Djamel Eddine Mansour, Technical Pre-Sales Project Manager at JA Solar, highlighted key milestones in the development of TOPCon technology products at the vertically integrated PV module company (see JA Solar's presentation here). Mansour divided his presentation into 3 categories: high-efficiency cell design optimization, high-efficiency module design optimization, and the redefining of modern module characterization.
Starting mass production of TOPCon cells with efficiencies of up to 25% in 2022 under the brand name BYCIUM+, JA Solar advanced to the 5th generation TOPCon cell structure by October 2024, named BCM5.0 and featuring 26.8% efficiency. Recently, JA Solar highlighted 2 significant advancements in the TOPCon cell technology: Laser-Enhanced Contact Optimization (LECO) and half-cell edge passivation.
The LECO process, which integrates laser technology with low-corrosion silver paste for cell metallization contact optimization in a low-temperature sintering process, boosts efficiency by 0.2% to 0.4%. Additionally, this efficiency improvement contributes to a module power gain of up to 10 W. However, challenges in this metallization advancement include the development of low-temperature, high-tensile main grid paste and the need for precise laser control in the reverse bias mode to ensure consistent contact performance.
JA Solar also noted that, unlike HJT cells, which are fabricated from half-wafer materials, the non-destructive laser-cutting process used for finished TOPCon cells results in efficiency losses of over 0.2%. To minimize these losses, the company adopted the edge passivation process, which involves depositing an aluminum oxide thin film along the cell edges using a low-temperature atomic layer deposition (ALD) process. This reduces interface recombination and passivates the surface to repel minority charge carriers. The technology resulted in a 0.19% efficiency gain and a 1.8 mV open-circuit voltage (Voc) increase, translating into a module-level power output gain of up to 6 W.
Following an analysis of cell-to-module (CTM) power loss simulation results from Fraunhofer ISE for a TOPCon module, JA Solar focused on 3 primary routes to recover power losses: geometrical loss, optical loss, and electrical loss. Geometrical losses can arise from factors such as wafer size, cell-to-cell gap changes, and metallization busbar configurations. Starting last year, JA Solar began using M10R (182 mm) size rectangular wafers to produce various modules by cutting them symmetrically or asymmetrically. The DeepBlue 4.0 Pro series module, equipped with M10R wafers, offers a power output of up to 650 W.
On the metallization front, the company has significantly increased the number of busbars, transitioning from multi-busbar to super multi-busbars (SMBB) and, ultimately, zero busbars (0BB). The 0BB metallization, which uses ultrafine round ribbons and electrical conductive adhesive (ECA) stringing technology, saves up to 20% of silver paste compared to traditional SMBB metallization. JA Solar explained that the busbarless layout, which reduces shading by 5% to 25% compared to SMBB cells, leads to higher light absorption rates and reduced incident angle modifier (IAM) losses, resulting in enhanced power output by up to 5 W and higher efficiency.
From an electrical loss perspective, the use of thin metallization wires reduces series resistance due to a shorter current transmission length on both sides of the cell busbar, boosting power output by minimizing series resistance losses. The 0BB metallization technology also improves contact between the wires and fingers, reducing power loss due to fewer microcracks, lower welding temperatures, and localized stress.
Additionally, with the 0BB high-efficiency module solution, JA Solar has achieved up to a 5% reduction in carbon emissions by optimizing auxiliary materials such as paste and welding wire films, in line with the company’s sustainable manufacturing practices. The company has also adopted advanced welding technologies that lower welding temperatures by 15% to 40%.
Beyond technology optimization at both the cell and module levels, JA Solar has adopted advanced module characterization processes, including AI-driven data analysis, in-field high-power performance with the best levelized cost of energy (LCOE), self-cleaning and anti-glare properties, and in-depth degradation pattern analysis.