About BURST

Context and perspectives

Recognizing the risks associated with relying on imports of PV products, the European Union has committed to support the establishment of gigawatt scale PV production within Europe as part of the European Green Deal.

Silicon PV technology is advancing towards terawatt-scale production, enabling a transition to cleaner energy systems and a climate-neutral economy. Among various technologies, interdigitated back-contact (IBC) solar cells are expected to achieve the highest power conversion efficiencies (PCE).

Nevertheless, the cost-effectiveness and applicability of this promising technology has still much room for improvement by reducing the absorber material thickness while keeping maximum performance. This is a major challenge that can be tackled by enhancing the cells’ absorption density through optical strategies assisted by advanced passivation schemes.

In line with this, increasing demand for ultra-thin solar cells has spurred extensive research for its advantages :

  • reduced material consumption leading to improved life cycle, weight reduction
  • potential mechanical flexibility for expanded application possibilities

BURST aims to improve the efficiency of Si IBC solar cells, targeting 26% with thin (<80 µm) and 27% with standard thick (300 µm) c-Si solar cells, without relying on critical materials like indium or silver.

Context-and-perspectives

Aim of the project and specific objectives

Aim-of-the-project-and-specific-objectives

BURST will develop the next generation of IBC solar cells with innovative and industrially scalable photonic light management, superior passivation schemes and Ag-free metallization.

Maximizing the absorption of light in ever thinner wafers requires advanced light management. BURST’s light trapping based on optimized photonic structures will demonstrate superiority over the state-of-the-art random pyramidal textures by absorbing >99 % of the theoretical limit. BURST will transfer lab-type fabrication processes to cost-effective, high-throughput industrial fabrication methods (TRL5) by using high precision, rapid laser patterning and atmospheric dry etching.

Advanced passivation and passivating contacts are essential to prevent recombination and harvest the extra charge carriers generated from the advanced light management. BURST’s IBC cell front side will achieve excellent passivation (enabling >750 mV) and high transparency. Alloying BURST’s excellent poly-Si passivating rear contacts with oxygen will mitigate parasitic absorption at the rear side. BURST will apply aluminium and copper as inexpensive and abundant materials with low-cost techniques to ensure a low-resistive contact (<1 mOhm.cm²) to the passivating poly-Si contact of the Ag-free BURST IBC cell.

Finally, the high-efficiency BURST cells will be assembled into mini-modules supplemented by detailed analysis of the costs, environmental impact, supply security and circularity to demonstrate the advantage of BURST technology in relevant environments.

For this, the specific objectives of the BURST project are:

  • Development and optimization of nanophotonic structures
  • Development and validation of passivation and metallization approaches
  • Implementation of BURST BBs in a relevant environment and in cells with highest efficiency
  • Proving the viability of implementing BURST BBs in industrial processes
  • Demonstrating the sustainability and viability of BURST technology

BURST methodology

BURST-methodology

BURST outcomes

Before BURST

Benefits

Si solar cells

  • Record efficiencies of Si solar cells: 26,8%
  • Light trapping with random pyramid texture: record short current densities of 43 mA/cm² with 300 µm absorbers
  • At least 26% efficiency with <80 µm c-Si solar cells and 27% with 300 µm c-Si solar cells
  • Novel light trapping allowing ultrathin cells with low CO2 footprint

Passivation

  • Front side passivation: AlOx, SiNy or a-Si
  • Passivation contacts: TOPCon with poly-Si-based contacts
  • Extremely high open-circuit voltages >>> 750 mV from ultrathin solar cells
  • Exploitation of full potential of novel light trapping

Metallization

  • Screen printed Ag
  • Consumption of ~15% of world’s total yearly Ag production and use of diffused/Al-BSF contacts
  • Novel Ag-free metallization of passivating contacts: 50 to 75% decrease in Ag consumption
  • BURST IBC solar cells do not require TCOs