The efficiency of silicon solar cells has a large influence on the cost of most photovoltaics panels. Here, researchers from Kaneka present a silicon heterojunction with interdigitated back contacts reaching an efficiency of 26.3% and provide a detailed loss analysis to guide further developments.

Silicon heterojunction solar cell with interdigitated back contacts for a photoconversion efficiency over 26

Exceeding conversion efficiency of 26% by heterojunction interdigitated back contact solar cell with thin film Si technology

Silicon heterojunction solar cells: Recent technological development and practical aspects - from lab to industry

For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%. The most efficient silicon solar cells use interdigitated back-contact silicon heterojunction architectures. Here, the authors fabricate this type of cell via a simpler process, using an interband silicon tunnel junction for the electron contact and reaching a certified efficiency higher than 22%.

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Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

Structural and optical properties of Ti and Cu co‐doped ZnO thin films for photovoltaic applications of dye sensitized solar cells

Analysis of edge losses on silicon heterojunction half solar cells

Back Contact Heterojunction Solar Cells Patterned by Laser Ablation

Recent Progress on the CEA-INES Heterojunction Solar Cell Pilot Line

CEA-INES Heterojunction Solar Cell ‘LabFab’ Industrial Pilot Line: Production Capability Demonstration, Roadmap to 22% Mean Efficiency

In this work, an emerging cell concept based on silicon homo-heterojunction (HHJ) is investigated. Compared to the n-type silicon heterojunction cell (HET), the HHJ architecture contains an additional thin and highly doped (p + )c-Si layer at the front (i)a-Si:H/(n)c-Si interface. Using numerical simulations, advantages of the alternative architecture are first underlined. Especially, passivation improvements brought by the (p + )c-Si layer are evidenced through the study of the recombination rates in the whole cell. From the simulation results, the manufacturing issues of the HHJ cell are then addressed. Due to the need of a fully activated and shallow (p + )c-Si layer, ion implantation of boron is a promising candidate for making such cells. However, the efficient (i)a-Si:H passivation is very sensitive to substrate quality. Thus, the high temperature post-implantation annealing effect on the Cz substrates should to be assessed. An anneal at 1050°C, often required to fully activate Boron implanted emitters, strongly decreases the substrate lifetime and will impact drastically the HHJ cell performance. A 950°C annealing is found to limit considerably the substrate degradation. However, such rather low temperature will limit the maximum doping concentration of the implanted layer and thus the maximum achievable VOC in HHJ devices.

Delfina Muñoz

Papers

Analysis of edge losses on silicon heterojunction half solar cells

Back Contact Heterojunction Solar Cells Patterned by Laser Ablation

Recent Progress on the CEA-INES Heterojunction Solar Cell Pilot Line

CEA-INES Heterojunction Solar Cell ‘LabFab’ Industrial Pilot Line: Production Capability Demonstration, Roadmap to 22% Mean Efficiency

5th International Conference on Silicon Photovoltaics, SiliconPV 2015 Silicon bulk issues during processing of homo-heterojunction solar cells