From Concept to Mass Production: Risen Energy's Journey with Ultra-Thin Silicon Wafer Technology

Introduction

The emergence of discussions surrounding space photovoltaic technology underscores several technical attributes imperative to the solar industry. Among these, lightweight construction, high efficiency, radiation resistance, and long-term reliability stand out. Leading the way in this transformation is Risen Energy, a company that has spent years developing and scaling ultra-thin silicon wafer technology utilized in heterojunction (HJT) solar cells.

The Importance of Thinness

In Risen Energy's recently released white paper, HJT Hyper-ion, pivotal insights into the production and application of ultra-thin wafers are explored. This document emphasizes that ultra-thin wafers, which make up 55% of the cost structure for HJT solar cells, represent the most direct and effective means of reducing costs in production. However, the rationale extends beyond mere economics; it is inherently tied to the structural benefits of HJT technology itself.

Using a low-temperature manufacturing process that operates below 200°C, HJT technology facilitates a more delicate handling of the wafers, significantly reducing the risks of deformation or breakage that accompany high-temperature processes found in other technologies like PERC and TOPCon. This compatibility not only enhances the performance but also acts as a catalyst for broader future applications within the solar sector.

Balancing Reliability and Efficiency

Through a series of investigative trials, Risen Energy examined efficiency, yield rates, and mechanical strength, revealing a nuanced relationship between these factors. While it was found that the short-circuit current (Jsc) decreases with wafer thinness, the open-circuit voltage (Voc) tends to increase. Remarkably, the fill factor (FF) remained consistent across various thicknesses. Risen's HJT Hyper-ion cells, fabricated with 110μm wafers, achieved an average efficiency of 26.4%, with some production batches surpassing 26.6%. These impressive figures demonstrate that thinner wafers do not compromise performance in HJT technology.

Production Optimization

To enhance production processes, Risen Energy shifted from horizontal to vertical wafer configurations, optimizing all associated automation and transfer steps within the line. The outcome was a consistent yield rate above 99.5%, with fragment rates under 0.25%. This illustrates that challenges brought about by wafer thinning can be mitigated through systematic innovations in production methods and equipment.

Mechanical Strength Retooled

Comparative tests revealed that while PERC cells of 150μm and TOPCon cells of 130μm failed during bending tests, HJT cells maintained excellent flexibility even when reduced to below 100μm. This resistance opens new possibilities for lightweight module designs and applications in specialized environments.

Expanding from Earth to Space

Currently, Risen Energy’s HJT Hyper-ion products utilize wafers that are 110μm thin, leading to solar cells roughly 95μm thick. This balance optimizes efficiency while substantially cutting costs. Importantly, for space photovoltaic applications—where a high power-to-weight ratio is crucial—solar cells often must have thicknesses of 70μm or less. Drawing on extensive experience with ultra-thin wafer technology, Risen Energy has developed the capability to manufacture cells thinner than 70μm.

Innovating Systemically for Durability

The traditional high-temperature soldering methods are no longer suitable for ultra-thin cells. In response, Risen has pioneered the Hyper-link technology, which prevents thermal stress during soldering. This innovation is backed by over 50 exclusive patents and aligns with the low-temperature characteristics of HJT technology and the physical demands of ultra-thin cells. Rigorous reliability tests demonstrate that Hyper-ion modules with ultra-thin wafers and Hyper-link technology exhibit performance degradation that significantly undercuts standard requirements.

Integrated R&D Approach

Risen Energy's journey towards ultra-thin wafers transcends mere technological breakthroughs; it incorporates integrated innovations spanning wafers, cells, and modules. This includes strategies for thinning wafers, low-silver metallization, busbar-free cells, and Hyper-link technologies—interlocking pieces that culminate in the high competitiveness of the Hyper-ion product line.

In conclusion, Risen Energy's path to ultra-thin wafers began as a response to industry cost-reduction demands and flourished through a commitment to technological integrity and systematic innovation. By revisiting this white paper, we aspire to reflect on our current phase of industry practice and invite collaboration with partners across the sector to propel photovoltaic technology towards a future that is lighter, stronger, and more inventive than ever before.