Pyridine-Functionalized Fullerene Electron Transport Layer for Efficient Planar Perovskite Solar Cells

Abstract

In regular perovskite solar cells (PSCs), the commonly used electron transport layer (ETL) is titanium oxide (TiO2). Nevertheless, the preparation of a high-quality TiO2 ETL demands an elevated-temperature sintering procedure, unfavorable for fabrication of PSCs on flexible substrates. Besides, TiO2-based devices often suffer from notorious photocurrent hysteresis and serious light soaking instability, limiting their potential commercialization. Herein, a novel pyridine-functionalized fullerene derivative [6,6]-(4-pyridinyl)-C61-ethyl acid ethyl ester (PyCEE) was synthesized and applied as an ETL to replace TiO2 in n–i–p PSCs. PyCEE-based devices achieved a champion power conversion efficiency (PCE) of 18.27% with significantly suppressed hysteresis, superior to that of TiO2-based devices. PyCEE has suitable energy levels and high electron mobility, which facilitate electron extraction/transport. Besides, the pyridine moiety within PyCEE affords coordination interactions with the Pb2+ ion within CH3NH3PbI3, passivating the trap states of CH3NH3PbI3 and thus improving the device performance and suppressing hysteresis greatly. Moreover, PyCEE ETLs were applied in flexible PSCs, achieving a PCE of 15.25%. Our results demonstrated the applicability of PyCEE ETLs in flexible devices and provided new opportunity for the commercialization of PSCs.

Room-temperature multiple ligands-tailored SnO2 quantum dots endow in situ dual-interface binding for upscaling efficient perovskite photovoltaics with high VOC

“…It is noted that the Pb 4 f 7/2 and Pb 4 f 5/2 of the 2AT-SnO 2 QDs/perovskite sample show lower binding energies of 138.57 and 143.47 eV, respectively. This is probably due to the fact that Pb ion accepts electron pairs from the functional groups within 2AT via coordination bonding 61 . These chemical interactions significantly passivate the trap states, resulting in a long carrier lifetime and suppressed hysteresis.…”

Progress in Materials Development for Flexible Perovskite Solar Cells and Future Prospects

“…[82] Other than metal oxide ETLs, organic materials have also been used as ETL largely because of their ease of lowtemperature solution processing. These include materials such as 6,6-phenyl-C 61 -butyric acid methyl ester (PCBM), [83][84][85][86][87] C 60 , [88][89][90] N,N-bis3-(dimethylamino)propyl-N',N'-dimethylpropane-1,3-diamine (CDIN), [91] [6,6]-(4-pyridinyl)-C 61 -ethyl acid ethyl ester (PyCEE), [92] and 1-benzyl-3-methylimidazolium chloride. [93] The fullerene derivative PCBM is widely used because of its solution processability and matching energy levels with the perovskite layer.…”

Pyridine‐functionalized fullerene derivative as an independent electron transport layer enabling efficient and hysteresis‐free regular perovskite solar cells

“…C 60 -3-BPy was synthesized via a facile one-step Prato reaction at 80 o C as reported previously. [26,27] C 60 -3-BPy was dissolved in chlorobenzene with concentrations of 5 mg ml :MABr = 1:0.2) was spin-coated onto the substrates with a two-step procedure. [17] The first step was 2000 rpm for 10 seconds with an acceleration of 200 rpm s −1 .…”

“…Recently, we reported a novel pyridine-functionalized fullerene derivative (C 60 -3-BPy) by a facile one-step method, which was applied as the ETL of inverted (p-i-n) MAPbI 3 -based PSCs, exhibiting a higher efficiency and stability than that of the control devices with conventional PCBM as ETL. [25][26][27][28] Whether such a pyridine-functionalized fullerene derivative can be applied as an independent ETL in n-i-p PSCs affording improved PCE remains an open question.…”