Cross-linked gap transport layers for high-efficiency perovskite tandem solar cells

The energy conversion effectivity (PCE) of single-junction perovskite solar cells (PSCs) has elevated remarkably from 3.8% to 25.2% in only a decade. As the speedy improvement of PCE has been approaching the restrict of its theoretical effectivity, fabricating tandem solar cells by combining subcells with completely different bandgaps provides an avenue to transcend the Shockley-Queisser limits of single-junction solar cells.

The tandem gadgets make the most of completely different components of the solar spectra utilizing subcells with completely different bandgaps to scale back the thermal lack of photo-generated carriers. Due to the tunable bandgap, excessive absorption coefficient and low fabrication price, metallic halide perovskites are promising candidates for tandem gadgets.

However, the effectivity of perovskite-based tandem solar cells is basically restricted by wide-bandgap top-cells which usually possess a big open-circuit voltage (V_OC) loss. The extreme nonradiative cost recombination on the interface between perovskite and gap transport layer (HTL) is a key issue resulting in the big V_OC loss.

Recently, analysis group of Prof. Hairen Tan from Nanjing University has used the cross-linked natural small molecule VNPB because the HTL for wide-bandgap perovskite solar cells. A V_OC enhance of practically 50 mV was efficiently obtained for wide-bandgap solar cells with bandgaps of 1.6 eV, 1.7 eV and 1.8 eV. Compared with the management gadget utilizing PTAA polymeric HTL, the perovskite movies deposited on VNPB have bigger grain dimension and higher crystallinity. VNPB permits quicker cost extraction and reduces defect density on the HTL/perovskite interface.

Density useful idea (DFT) calculation reveals that the nearer contact between VNPB and perovskite will increase the defect formation vitality and reduces the defect density, thus successfully lowering the non-radiative recombination of carriers. Finally, the PCEs of perovskite/perovskite and perovskite/silicon tandem solar cells utilizing VNPB as HTL attain 24.9% and 25.4%, respectively.

This work reveals that cross-linkable small molecules are promising for high-efficiency and cost-effective perovskite tandem photovoltaic gadgets.