2022 Advanced Materials (IF30.849 ): How Ternary Tin (II) Alloy can be used as tin-lead perovskite solar cells Hole transport layer to achieve high efficiency and stability?

Tin-lead (Sn-Pb) narrow bandgap (NBG) perovskites show great potential in both single-junction and all-perovskite tandem solar cells. Sn-Pb perovskite solar cells (PSCs) are still limited by low charge collection efficiency and poor stability.

Advanced Materials published a study in September 2022: its reported a ternary Sn (II) alloy of SnOCl as the hole-transport material (HTM) with a work function of 4.95 eV for Sn-Pb PSCs. The solution processed SnOCl layer has a texture structure which not only reduces the optical loss of the devices but also changes grain growth of Sn-Pb perovskites and boosts the carrier diffusion length to 3.63 μm. The formation of small perovskite grains at the HTM/perovskite interface is suppressed. These result in an almost constant internal quantum efficiency of 96 ± 2% across the absorption spectrum of Sn-Pb perovskites. The SnOCl HTM significantly enhances the stability of Sn-Pb PSCs with 87% of its initial efficiency retained after 1-sun illumination for 1,200 h, and keep 85% efficiency under 85°C thermal stress for 1,500 h.

The hybrid HTM further improve the stabilized efficiencies of single-junction Sn-Pb PSCs and all-perovskite tandem solar cells to 23.2% and 25.9%, respectively. This discovery opens an avenue to the multi-component metal alloys as HTM in PSCs.

Figure 1. Fabrication of the SnOCl hole-transport layer (HTM). (a) Current density-voltage (J-V) curves for Sn-Pb perovskite solar cells (PSCs) using SnOCl fabricated from SnCl² precursor solutions with varied PH values. The PH value of SnCl² solution is controlled by adding NaOH with different percentage. (b) J-V curves for Sn-Pb PSCs using SnOCl annealed at varied temperature from RT (~27 °C) to 150 °C in a N₂ -filled glovebox. The photovoltaic (PV) parameters for all the Sn-Pb PSCs (8 mm² device area with a 5.9 mm² photomask) were determined by the J-V measurements under reverse scanning at 0.05 V s-1.

Fig. 2. Optimization of the thickness for SnOCl as HTM in Sn-Pb PSCs. PV parameter statistic for Sn-Pb PSCs using SnOCl as HTMs fabricated from SnCl2 solutions with different concentrations. 12 devices for each concertation are fabricated for statistic. The PV parameters for all the Sn-Pb PSCs (8 mm² device area with a 5.9 mm² photomask) were determined by the J-V measurements under reverse scanning at 0.05 V s-1 .

Fig. 3. J-V curves for the champion all-perovskite tandem solar cells using PEDOT:PSS and only SnOCl as HTMs for the NBG sub-cells under reverse scanning, respectively.

Key word: perovskite solar cell, Stability, all-perovskite tandem solar cells

Article link: https://onlinelibrary.wiley.com/doi/epdf/10.1002/adma.202205769