JinkoSolar has unveiled its first back-contact solar cell technology, combining TOPCon and heterojunction passivation in a new architecture called TAC. The Chinese manufacturer reported a peak cell conversion efficiency of 28%.
Chinese PV module maker JinkoSolar unveiled its TOPCon-based Amorphous-Si Passivating Cell (TAC) technology at its Global Tech Day event in Shanghai on Oct. 17. According to a technical white paper published by the company, the architecture combines TOPCon electron-selective contacts with heterojunction (HJT) hole-selective contacts and a rear-electrode layout.
The design uses an n-type crystalline silicon wafer with two alternating carrier-selective contact regions on the rear surface. Both positive and negative electrodes are located on the rear, eliminating front-side metallization and the associated optical shading losses.
The electron-collecting n-type region retains the contact structure used in TOPCon cells, consisting of an approximately 1 nm to 2 nm silicon oxide tunneling layer and heavily doped polycrystalline silicon. This structure enables selective electron transport with low contact resistance while suppressing carrier recombination.
The hole-collecting p-type region uses intrinsic and doped hydrogenated amorphous silicon (a-Si), drawing on HJT cell technology. JinkoSolar said the configuration improves surface passivation and open-circuit voltage. A transparent conductive oxide (TCO) layer facilitates lateral carrier transport, while the amorphous silicon passivation process takes place at temperatures below 200 C.
High-precision laser patterning and dielectric isolation separate the two contact regions. JinkoSolar describes the architecture as a “2+1” design, combining TOPCon electron contacts, HJT hole contacts and a rear-electrode structure.
TAC belongs to the broader back-contact (BC) cell category, which includes architectures using different passivation and carrier-selective contact technologies. Unlike conventional front-contact TOPCon cells, TAC eliminates front-side metal contacts to reduce shading losses. Its distinguishing feature among BC technologies is the integration of TOPCon and amorphous silicon heterojunction contacts on the same wafer.
JinkoSolar has also developed a full-area passivation approach, called the Global Passivation Process (GPP), to reduce recombination losses across the contact regions. Another process, Multi-Dimensional Charge Passivation (MCP 2.0), targets carrier recombination at cut-cell edges. It uses a cut-before-passivation sequence, followed by chemical, field-effect and hydrogen passivation of the exposed surfaces.
Other cell-level features include high-purity, low-oxygen n-type silicon wafers and a light-trapping structure combining surface texturing, antireflection coatings and rear reflection. The white paper specifies a bulk minority-carrier lifetime exceeding 2 ms and a bulk recombination current density below 5 fA/cm² for the silicon substrate.
JinkoSolar said TAC production cell efficiency has exceeded 27%, with a peak efficiency of 28%. The company’s Oct. 17 announcement identifies the 28% figure as peak cell efficiency. However, the white paper does not specify a third-party certification, test area or average production-line efficiency for the result.
In its first-half 2026 financial report, JinkoSolar separately reported a third-party-certified conversion efficiency of 27.2% for an n-type BC research cell. The company, however, did not identify that result as a TAC measurement.
JinkoSolar identified low-temperature metallization, copper-containing contact materials and the potential use of TAC as a bottom-cell platform for perovskite-silicon tandem devices as areas for further development.
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