Kaneka establishes perovskite/heterojunction crystalline silicon tandem solar cells with 29.2% effectiveness

• Japan-based chemicals business, Kaneka, has actually reported the design of a two-terminal (2T) perovskite-crystalline tandem solar cell making use of a 145 μm thick commercial Czochralski (CZ) silicon wafer.

The cell has an anti-reflection intermediate layer depending on what Kaneka calls "gentle textured structures" that were used on the front side of the bottom, which apparently makes it possible for a significant improvement in the typical light arrest effects in perovskite-silicon tandem devices.

" Light management technology is mandatory to fully utilize the vast array of the solar spectrum in a solar cell, particularly for a 2T tandem structure, because its top and lower cells are electrically attached in series and called for to satisfy the restrictions of current matching where the corresponding currents at the operating factor are straightened to some extent," the researchers claimed in their work. "Due to the big distinction in the refractive indices in between perovskite and crystalline silicon (c-Si) materials, the maximized intermediate layer as revealed work as an anti-reflection coating to suppress the reflection loss of the infrared light that is utilized in the bottom cell."

Kaneka controlled the morphology of the texture on both sides of the wafer by utilizing chemical etching. Via atomic force microscopy (AFM), it compared the performance of both absorbers with the gentle structure with that said of similar devices without the structure. "By using the gentle texture, the photocurrent thickness of silicon bottom cell boosts by over 2% from the recommendation," the business described.

The group fabricated a top cell with a substrate made from indium tin oxide (ITO), an electron transportation layer constructed from buckminsterfullerene (C60), a passivation layer, the perovskite absorber, a self-assembled monolayer, an intermediate layer based upon ITO and microcrystalline silicon oxide (μc-SiOx). It then fabricated the bottom cell with n-doped amorphous silicon (a-n: Si) layer, numerous silicon layers treated with different processes, as well as a bottom contact made of ITO and silver (Ag).

"The passivation layer was presented between C60 as well as perovskite layer and the densities of c-Si wafer as well as top ITO layer were lowered in this work," the scientists described. "After coating the passivation layer, C 60 was thermally evaporated together on the perovskite film".

The tandem device achieved a power conversion efficiency of 29.2%, an open-circuit voltage of 1.929 V, a short-circuit current thickness of 19.5 mA centimeters − 2, and also a fill variable of 77.55%. The result, which was reportedly verified by Fraunhofer ISE Callab, improves the 28.3% performance Kaneka had actually formerly accomplished for a device with the exact same style, with the main differences being the passivation layer and also wafer thickness.

"This is the highest licensed power conversion performance of 2T perovskite-silicon tandem solar cells utilizing CZ wafer to our knowledge," the firm claimed, keeping in mind that they are currently taking into consideration relocating to a four-terminal (T4) configuration for the more development of the device.