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Solution-Processable Ionic Liquid as an Independent or Modifying Electron Transport Layer for High-Efficiency
Qiliang Wu1, Weiran Zhou1, Qing Liu1
1Hefei National Laboratory for Physical Sciences at Microscale, Key Laboratory of Materials for Energy Conversion, Chinese Academy of Sciences, Department of Materials Science and Engineering, Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China (USTC) , Hefei 230026, China.
Ionic liquid ([EMIM]PF6) interface engineering significantly boosts perovskite solar cell efficiency by improving electron transport. Using ionic liquid as a TiO2 modifier enhanced power conversion efficiency to over 18%.
Area of Science:
- Materials Science
- Renewable Energy
- Nanotechnology
Background:
- Titanium dioxide (TiO2) is a common electron transport layer (ETL) in perovskite solar cells (PSCs).
- TiO2 faces challenges like high electron recombination and poor low-temperature processability in PSCs.
- Ionic liquids (ILs) offer potential for improved interface engineering in PSCs.
Purpose of the Study:
- To investigate ionic liquid (IL) interface engineering for planar heterojunction perovskite solar cells (PHJ-PSCs).
- To evaluate the performance of 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF6) as a TiO2 modifying interlayer and as an independent ETL.
- To understand the role of ILs in enhancing electron transport and device performance.
Main Methods:
- Application of [EMIM]PF6-IL as a TiO2 modifying interlayer in CH3NH3PbI3 PHJ-PSCs.
- Utilization of [EMIM]PF6-IL as an independent ETL in CH3NH3PbI3 PHJ-PSCs.
- Systematic investigation of IL effects on perovskite film morphology, crystallinity, optical absorption, and interfacial properties.
Main Results:
- CH3NH3PbI3 PHJ-PSCs with [EMIM]PF6-IL modified TiO2 ETL achieved an average power conversion efficiency (PCE) of 18.42 ± 0.65%, significantly outperforming standard TiO2 ETLs (14.20 ± 0.43%).
- The highest PCE reached 19.59%, nearing the record for planar CH3NH3PbI3 PSCs.
- Using [EMIM]PF6-IL as an independent ETL yielded an average PCE of 13.25 ± 0.55%, comparable to independent TiO2 ETLs (14.96%).
- Both methods demonstrated effective electron transport facilitated by the IL.
Conclusions:
- Ionic liquid interface engineering, particularly using [EMIM]PF6 as a TiO2 modifier, offers a promising strategy to enhance PCE in PHJ-PSCs.
- ILs effectively promote electron transport and improve interfacial properties in perovskite solar cells.
- [EMIM]PF6 presents a viable alternative or additive for ETLs in low-temperature processed perovskite solar cells.
