Trina Solar unveils THBC technology, TOPCon’s next frontier?

Decoding THBC: a pioneering fusion of three core technologies

As competition intensifies among PV technology pathways, Trina Solar’s THBC technology stands out as more than a mere combination of existing solutions. It is a structural innovation designed to meet the real-world needs of the solar industry.

THBC stands for TOPCon-Compatible Hybrid Back-Contact Cell. Its full name—TOPCon-compatible hybrid passivated back-contact cell—clearly defines the core attributes of this technology.

Xie Zhigang, chief scientist at Trina Solar Central Research Institute, explained: “Built on the well-established industrial ecosystem of TOPCon, THBC combines the passivated contact technology of TOPCon, the high-efficiency passivation enabled by amorphous silicon in HJT, and the front-side grid-free design of BC cells. This integration delivers a brand-new solar cell architecture, making THBC an exceptional technology that leverages the strengths of three leading cell technologies.”

He further explained that PV technologies have long been divided into two distinct ecosystems: high-temperature and low-temperature processes. PERC and TOPCon belong to the high-temperature ecosystem, while HJT defines the low-temperature side. These two technical routes have largely developed independently. The core breakthrough of THBC lies in its unprecedented ability to bridge the gap between high-temperature and low-temperature processes, enabling an innovative “high-low temperature hybrid passivation”. This unique design effectively integrates the superior passivated contact performance of TOPCon with the high-efficiency passivation capability of HJT, while incorporating an advanced back-contact electrode structure.

This hybrid passivation mechanism effectively addresses the inherent limitations of conventional TBC technology, which relies solely on high-temperature diffusion passivation. Traditional TBC simply relocates the front-side grid lines of TOPCon cells to the rear while leaving the core technical architecture unchanged. THBC, by contrast, represents a structural redesign. It adopts an “intrinsic silicon + TCO” structure, minimising rear parasitic absorption and significantly improving passivation performance.

Xie Zhigang further elaborated on the value of this structural innovation. Traditional TBC relies on single-step, high-temperature diffusion homojunction passivation, which inherently limits hole extraction. This flaw often leads to inadequate passivation and lower conductive performance.

THBC replaces conventional high-temperature diffusion by using low-temperature heterojunction deposition. Specifically, it employs a hole-selective emitter to replace the traditional high-temperature boron diffusion tunnelling junction, achieving superior surface passivation while effectively resolving the issue of excessive contact resistance.

Additionally, with due consideration for material weatherability and long-term operational durability, THBC optimises vertical interface conductivity through a selective enhancement design, further strengthening the reliability of the technology.

With the innovative THBC technology, Trina Solar aims to approach the theoretical efficiency limit of c-Si single-junction cells. This technological pursuit stems from the company’s deep awareness of the industry’s current challenges. After multiple rounds of technical upgrades, mainstream PV technologies have all reached clear efficiency bottlenecks, while emerging next-generation solutions typically require massive investments in new production lines. Against the backdrop of industry overcapacity, a complete, ground-up technological revolution is neither cost-effective nor practically feasible for the PV sector.

“In the face of ongoing industry overcapacity, it is critical to fully leverage the massive existing TOPCon capacity while making only targeted, incremental investments,” said Zhang Yingbin, head of the New Product Technology Center at Trina Solar’s PV Product Business Division. “Specifically, the low-temperature process segment of THBC can fully utilise existing industry assets, production capabilities, and mature technological reserves.”

Trina Solar’s approach to industrialising THBC reflects a philosophy of pragmatic technological innovation. It supports direct retrofitting of existing TOPCon mass-production lines while eliminating the need to build entirely new, standalone production facilities. As a result, it offers significant advantages in delivery flexibility, capital investment requirements, and cost structure over conventional TBC technology.

Trina Solar defines this differentiated roadmap as an industrialisation strategy of “forging ahead where possible and consolidating strengths where necessary.” In terms of capacity upgrades, THBC manufacturing is achieved by retrofitting TOPCon production lines, with additional equipment largely limited to PECVD and laser systems. This brings capital expenditure down to just one quarter to one third of that required for dedicated HJT production lines.

TOPCon and THBC: a dual-wheel drive

Within Trina Solar’s strategic framework, THBC and TOPCon together form a product matrix driven by “dual-wheel drive and mutual complementarity”.

“From a product and technical standpoint, PV application scenarios can be clearly divided into bifacial and mono-facial power generation, accounting for roughly 85% and 15% of the market, respectively,” Zhang Yingbin explained. “The inherent physical structures of these two technologies define their optimal application scenarios and market positioning.”

Under this differentiated framework, THBC features a full rear grid line design with zero shading on the cell’s front surface, maximising front-side power conversion efficiency. This makes it ideally suited for mono-facial power generation scenarios, particularly residential rooftop systems.

In contrast, TOPCon delivers superior combined front-and-rear power generation performance, offering maximum customer value for ground-mount power plants that support dual-sided light absorption.

Ni Lili, President of Trina Solar’s PV Product Business Division, commented: “THBC capacity planning will be dynamically optimised in response to evolving market demand, with a particular focus on high-value markets such as Europe and Australia. THBC and TOPCon are not mutually exclusive substitutes but scenario-based complementary technologies. For mono-facial rooftop projects, THBC is the premier solution, while TOPCon remains the dominant choice for bifacial power plants.”

In terms of cost performance, although THBC incorporates heterojunction deposition processes, Trina Solar has achieved effective process optimisation to avoid significant manufacturing cost increases. While the THBC workflow involves a modest increase in process steps, the company has streamlined production by integrating laser processes and resolving compatibility challenges between high-temperature and low-temperature procedures, ensuring feasible mass production and stable yield rates.

Ni Lili disclosed that Trina Solar has completed construction of its THBC pilot production line, with formal capacity expansion currently underway. A gradual capacity ramp-up is scheduled within the year, demonstrating the company’s strong confidence in THBC industrialisation.

From a long-term strategic perspective, THBC represents an inevitable evolution for the TOPCon technology platform, enabling further efficiency gains and differentiated application deployment.

Meanwhile, industry insiders note that some TBC players have adopted aggressive cost-reduction strategies to gain a foothold in the utility-scale power plant market. These measures include drastically cutting silver paste consumption and making early attempts at copper paste substitution. While such tactics lower manufacturing costs, they introduce potential technical and operational uncertainties.

These hidden risks could compromise long-term module reliability, accelerate power degradation, and undermine power generation stability—all of which still require rigorous validation through large-scale mass production and long-term field operation.