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CSEM, EPFL reveal technical details of 31.25%-efficient tandem perovskite-silicon solar cell – pv magazine International


A yr after attaining what was a world document effectivity for a tandem perovskite-silicon photo voltaic cell on the time, scientists from EPFL and CSEM printed a paper displaying the technical options of the gadget and the way the outcome was made potential. The secret’s to manage the perovskite crystallization course of utilizing an additive within the processing sequence.

the The Swiss Middle for Electronics and Microtechnology (CSEM) and the École polytechnique fédérale de Lausanne (EPFL) introduced in June 2022 that they’d achieved an influence conversion effectivity of 31.25% for a 1 cm2 tandem perovskite-silicon photo voltaic cell, which they are saying represents, on the time, a world document for a PV gadget of this kind.

The 2 scientific establishments, nonetheless, didn’t launch many particulars in regards to the cell know-how and the way the brand new document was achieved. Now, greater than a yr later, they introduced the cell and associated manufacturing processes within the paper “Interface passivation for 31.25%-efficient perovskite/silicon tandem photo voltaic cells,” printed final week. on Science.

“Our staff took a pioneering method by designing a tandem photo voltaic cell with a perovskite layer conformally coated on a silicon backside cell,” the lead writer of the analysis, Xin-Yu Chin, mentioned. pv journal. “The silicon backside cell has micrometric pyramids, an industry-standard innovation that enhances its photocurrent era.

One of many key challenges in perovskite/silicon tandem cells is the recombination losses that happen on the perovskite prime floor interfacing within the electron selective contact. Recombination is a course of during which photogenerated cost carriers – electrons and holes – recombine earlier than they are often collected and used to supply electrical energy, resulting in a lack of effectivity. “To handle this concern, we included an additive within the processing sequence, which has confirmed instrumental in regulating the crystallization means of perovskite,” defined Chin. “This step effectively passes the interface, which successfully reduces the recombination losses that hinder the general efficiency of the cell.”

The scientists used a phosphonic acid referred to as 2,3,4,5,6-Pentafluorobenzylphosphonic acid (FBPAc) to passivate the perovskite absorber and one other phosphonic acid known as methyl-substituted carbazole (Me-4PACz) to take away passivated interfacial defects within the gap transport layer (HTL).

The cell relies on a substrate fabricated from glass and indium tin oxide (ITO), a Me-4PACz HTL, an absorber fabricated from FABr:FAI perovskite with an vitality bandgap of 1.70 eV, a buckminsterfullerene (C60) electron transport layer, a bathocuproine (BCP) buffer layer, and a prime electrode based mostly on copper (Cu).

Examined underneath normal lighting situations, the gadget confirmed an effectivity of 31.25%, an open-circuit voltage of 1.91 V, a short-circuit present of 20.47 mA/cm2, and a fill issue of 79.8%, all of that are licensed by the US Division of Vitality’s Nationwide Renewable Vitality Laboratory (NREL).

“Using Me-4PACz reduces the voltage loss on the perovskite / HTL interface, whereas the inclusion of FBPAc within the perovskite deposition sequence reduces the voltage loss on the perovskite / C 60 ETL interface and results in extra favorable perovskite microstructures with bigger domains,” the researchers emphasised, including that the The outcome additionally exhibits that the know-how is able to advance to the subsequent stage of its improvement, which requires a central give attention to stability and scalability points.

“It’s potential that the know-how will take one other 5 to 10 years to enter the market. Present industrial options are already relevant to all thin-film supplies utilized in tandem photo voltaic cells, as demonstrated by the brand new Oxford PV outcomes,” added Chin. “The primary concern that the scientific neighborhood wants to handle is the sturdiness of the perovskite materials. Can these supplies be sturdy sufficient to outlive for greater than 20 years in sensible purposes? That is what issues. that query will decide the business success and influence of this know-how.”

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