Conceived by Chinese scientists, the cell was built with new surface reconstruction strategy based on the use of 1,4-butanediamine (BDA) and ethylenediammonium diiodide (EDAI2) as surface modifiers. The device was able to retain 79.7% of its initial efficiency after 550 h.A group of researchers from the Huazhong University of Science and Technology in China has fabricated an all-perovskite tandem solar cell with a wide-bandgap tin-lead (Pb-Sn) perovskite top cell based treated with a novel surface reconstruction strategy aimed at reducing Sn defects.
The proposed strategy is reportedly able to create high-quality Sn–Pb mixed perovskite films that can help reduce non-radiative energy losses at the perovskite-electron transport layer interface. It consists of using 1,4-butanediamine (BDA) and ethylenediammonium diiodide (EDAI2) as surface modifiers, which reportedly yields a close-to-ideal stoichiometric ratio and uniform surface potential, as well as well-aligned Femi-levels.
The group built a 0.0871 cm2 cell with the treated Sn-Pb perovskite absorber, an electron transport layer (ETL) based on buckminsterfullerene (C60), a hole transport layer (HTL) based on PEDOT-PSS, and a gold (Au) metal contact.
The best-performing BDA-EDAI2 modified device achieved a power conversion efficiency of 28.80%, an open-circuit voltage of 2.13 V (2.13 V), a short-circuit current density of 16.06 mA cm−2, and a fill factor of 84.19%. “We also verified the effectiveness of the surface reconstruction in module-level devices and obtained a champion PCE of 23.39% with an aperture area of 11.3 cm2,” the academics stated.
Furthermore, they found that the encapsulated tandem cells retained 79.7% of their initial efficiency after continuous operation under maximum power point tracking (MPPT) in ambient air for 550 h.
An unspecified third-party organization also certified that the best-performing devices achieved an efficiency of 28.49%, which the research group described as one of the highest efficiencies ever reported for all-perovskite solar cells.
“Impressively, our Sn–Pb mixed PSCs with BDA-EDAI2 modification showed PCEs of 22.65% and 23.32% for 1.32 and 1.25 eV bandgap, respectively, and with largely increased open-circuit voltage and fill factor,” the academics concluded.
The new cell concept was introduced in the study “Surface chemical polishing and passivation minimize non-radiative recombination for all-perovskite tandem solar cells,” published in nature communications.