A Multifunctional Molecular Bridging Layer for High Efficiency, Hysteresis‐Free, and Stable Perovskite Solar Cells

Abstract

At present, the dominating electron transport material (ETL) and hole transport material (HTL) used in the state-of-the-art perovskite solar cells (PSCs) are tin oxide and 2,2′,7,7′-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (Spiro-OMeTAD). However, the surface hydroxyl groups of the SnO 2 layer and the Li + ions within the Spiro-OMeTAD HTL layer generally cause surface charge recombination and Li + migration, significantly reducing the devices' performance and stability. Here, a molecule bridging layer of 3,5-bis(fluorosulfonyl)benzoic acid (FBA) is introduced onto the SnO 2 surface, which provides appropriate surface energy, reduces interfacial traps, forms a better energy level alignment, and, most importantly, anchors (immobilizes) Li + ions in the ETL, and consequently improves the device power conversion efficiency (PCE) up to 24.26% without hysteresis. Moreover, the device with the FBA passivation layer shows excellent moisture and operational stability, maintaining over 80% of the initial PCE after 1000 h under both aging conditions. The current work provides a comprehensive understanding of the influence of the extrinsic Li + ion migration within the cell on the device's performance and stability, which helps design and fabricate high-performance and hysteresis-free PSCs.

Molecule-bridged electron-selective contact for high-efficiency halide-based perovskite solar cells

“…After the introduction of H 2 Mi, we found that the characteristic peaks of Pb 4f 7/4 and Pb 4f 5/4 shifted 0.12 eV to the high binding energy, indicating that there is a strong chemical reaction between H 2 Mi and Pb 2+ to coordinate the uncoordinated Pb 2+ so that the defects of lead ions on the perovskite surface can be effectively passivated. 26 Similarly, the two characteristic peaks attributed to I 3d 5/2 and I 3d 3/2 in the perovskite film also increase from the initial 619.24 eV and 630.71 eV to 619.37 eV and 630.91 eV (Fig. 2e).…”

Quantitative Surface Passivation Through Drop‐on‐Demand Inkjet Printing Enables Highly Efficient Perovskite Solar Cells

“…As shown in Figure 4e, the 2.5 µg cm −2 2‐ADAHCl‐treated device maintained 92% of its original PCE after 1041 h of MPP tracking, whereas the control device showed a degradation to 80% of its original PCE after 158 h. The significantly improved operational stability can be attributed to greatly suppressed defects and ion migration after incorporating an appropriate amount of the passivator. [ 62,65,72 ] In addition, the thermal stability tests were performed by heating the unencapsulated devices at 85 °C in a nitrogen‐filled glove box. As shown in Figure S21 (Supporting Information), the efficiency of the control device dropped dramatically after heating for 3000 min.…”

Small molecule-incorporated SnO2 layer for efficient perovskite solar cells

“…This indicates additional chemically adsorbed oxygen on the surface of the SnO 2 :SSB film, which reduces the surface hydroxyl groups of SnO 2 and leads to ion recombination. 39…”