Researchers from METU-GÜNAM demonstrated a fully screen-printed, lithography- and laser-free IBC manufacturing route
The process uses patterned SiNx diffusion barriers for selective rear-side doping
First demonstrator IBC cells reached 19.3% efficiency using standard industrial tools
Interdigitated back contact (IBC), one of the leading back-contact (BC) solar cell architectures, remains among the most efficient silicon solar architectures available today. By placing all metal contacts on the rear side, the design eliminates front-side shading losses and improves optical utilization. Yet, despite record cell efficiencies exceeding 26%, IBC remains a niche technology in mass production due to the complexity and cost of rear-side patterning and selective doping.
Researchers from Turkey’s METU-GÜNAM have now proposed a simplified route to IBC manufacturing that could help reduce those barriers. In a paper published in Solar Energy Materials and Solar Cells, the team demonstrated a fully screen-printed, lithography- and laser-free fabrication process for IBC solar cells using only industrially established equipment.
Instead of relying on laser patterning, lithography, or ion implantation to define rear-side interdigitated p+ and n+ regions, the researchers used patterned silicon nitride (SiNx) diffusion barriers created through screen printing and wet etching. The process starts with the deposition of a conformal SiNx layer by PECVD over the wafer surface. A screen-printed acid-resistant etch mask is then applied in the desired rear-side pattern, followed by hydrofluoric acid etching to remove exposed SiNx. The remaining SiNx regions act as diffusion barriers during boron and phosphorus diffusion, enabling the selective formation of emitter and BSF regions without dopant pastes or dedicated laser systems.
To optimize the barrier layer, the team evaluated both Si-rich and N-rich SiNx films across multiple thicknesses. N-rich SiNx showed superior etchability and cleaner pattern definition during wet processing. A 120 nm N-rich SiNx layer provided the best balance of pattern fidelity and diffusion blocking, successfully preventing parasitic dopant crossover during high-temperature BCl₃ and POCl₃ diffusion.
Using this approach, the researchers produced well-confined boron- and phosphorus-doped rear-side regions suitable for IBC operation. For surface passivation, Al₂O₃/SiNx stacks delivered the best results, yielding implied open-circuit voltages of around 650 mV to 660 mV after firing. Rear metallization was completed using commercially available fire-through Ag and AgAl screen-printing pastes. Contact resistivities below 10 mΩ·cm² were achieved for both polarities when fired above 855°C, demonstrating compatibility with standard conveyor belt firing.
The team fabricated the first demonstrator IBC devices in both front floating emitter (FFE) and front surface field (FSF) configurations. The best-performing FFE device achieved 19.3% efficiency, with a Voc of 642 mV, Jsc of 37 mA/cm², and a fill factor of 71.2%. The best FSF variant reached 19.1%. While these values remain well below state-of-the-art IBC performance, the authors note that the results represent the first functional demonstration of the simplified process flow.
The detailed findings are published in the paper titled A fully screen-printed, lithography-free manufacturing route for interdigitated back contact silicon solar cells.
