Researchers Achieve 21.1% Efficiency with 20-μm Thin Monocrystalline Solar Cell


Hangzhou Dianzi University Researchers invented a 20-μm thin 21.1% efficient monocrystalline solar cell using an innovative method called layer transfer (LT). They achieved incredible improvements in short-circuit current, open-circuit voltage, fill factor, and overall cell efficiency, going from 16.5% to an exceptional 21.1%, by implementing passivation layers and utilizing distinct contact configurations. This would further improve solar cell performance, enable cost-effective use of silicon solar power, and revolutionize panel manufacturing.

Hangzhou Dianzi University researchers in China have successfully developed a thin film p-type monocrystalline solar cell with a power conversion efficiency that rivals its industrial thick counterparts.

Leonidas Palilis said, “Overall, the findings of this study present a novel way to realize high-performance thin crystalline silicon solar cells using much less silicon—for a 20-μm cell, around one eighth of the amount required for a thick 160-μm cell on a given panel size.”

The scientists in their published research paper explained that they used a method called layer transfer (LT) instead of cutting silicon ingots to produce the wafer for the solar cell. LT allows for the transfer of a layer of semiconductor material from one substrate to another.

This method involves:

  • The initial electrochemical use of hydrofluoric (HF) acid to etch pores into a thick silicon wafer, creating a porous silicon substrate.
  • This substrate is then utilized for the epitaxial growth of a monocrystalline silicon layer.
  • Finally, the epitaxial thin silicon layer is detached from the porous silicon substrate.

Using this method, the scientists successfully acquired a thin monocrystalline p-type silicon wafer that is 20μm thin. To enhance the performance of the cell, they applied a number of passivation layers, consisting of aluminum oxide (Al2O3), silicon nitride (SiO2) and silicon monoxide (SiOx), at the front of the cell using Plasma Enhanced Chemical Vapor Deposition (PECVD).

The contacts come in two distinct configurations and are said to enhance light absorption in both shorter and longer wavelengths. Consequently, this leads to a remarkable improvement in the short-circuit current and open-circuit voltage of the cell. The configurations are as follows:

  • SiO2/SiNx/SiOx
  • Al2O3/SiNx/SiOx

“Compared with a standard solar cell used as a reference, the current density increased from 34.3 mA/cm2 to 38.2 mA/cm2,” the researcher said, adding that the passivation layers also contributed to raising the cell open-circuit voltage from 632 mV to 684 mV.

Consequently, the device’s fill factor and cell efficiency witnessed remarkable growth:

  • Rising from 76.2% to an impressive 80.8%.
  • Surging from a modest 16.5% to an outstanding 21.1%.

Leonidas Palilis explained, “This advance will likely contribute to more widespread cost-effective adoption of silicon solar power technology, due to the reduced cost and the concomitant expansion of the solar panel manufacturing capacity.”

Source: Investigation on significant efficiency enhancement of thin crystalline silicon solar cells

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