Published TCIMAIL newest issue No.196
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Since the first report published by Miyasaka et al. in 2009,1) research and development of metal halide perovskite solar cells (PSCs) have been carried out as a solar cell that can achieve high performance using solution process, and the power conversion efficiency (PCE) of the solar cells has reached 26%.2) Leading research institutes and industries that promote solar cell research try to upscaling and modularization of practical PSCs. However, many challenges such as improving the stability of the devices still remain in commercializing PSCs. In order to solve the problem, development of new hole transport materials and optimizing the composition of perovskite layers are mainly conducted.
The widely used hole transport materials (HTMs), Spiro-OMeTAD and PTAA, are too expensive for the production of low cost PSCs. Also, some additives such as lithium salts and cobalt complexes, which cause deceasing of device stability, have to be used to enhance PCE of devices.
TCI has developed new HTMs TOP-HTM-α1 (Product No. B5672) and TOP-HTM-α2 (Product No. T3722). These HTMs are available at reasonable prices. MAPbI3-based PSCs based on TOP-HTM-α1 and TOP-HTM-α2 exhibit significant PCEs both with and without additives, and these devices also show superior device stability than device based on Spiro-OMeTAD (Application 1).3) In addition, PSCs based on TOP-HTM-α2 could exhibit higher PCE and superior device stability by composition engineering of perovskite layer from MAPbI3 to FAPbI3 (Application 2).4) Furthermore, TOP-HTM-α2 with additives shows superior PCE with improvement of hole transport layer (HTL) morphology by selection of solvent (Application 3).5)
Advantages
- Realize a high PCE both with and without additives.
- Realize a highly stable perovskite solar cell with low cost.
- Even higher PCE and superior device stability could be realized by tuning the compositions of perovskite layer.
Device Fabrication Process
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Preparation of HTM solution
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HTMs are dissolved in solvents at concentration of 40 mg/mL.
- With additives
Chlorobenzene is used as a solvent. LiTFSI and TBP are added to HTM solution. - Without additives
1,1,2,2-Tetrachloroethane is used as a solvent.
- With additives
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Fabrication of devices
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- In a glove box filled with nitrogen gas, hole transport layers are deposited on the perovskite layer by spin-coating (slope 5 seconds, 4000 rpm 30 seconds, slope 5 seconds).
- The resulting film is dried on a hot plate at 70 ˚C for 30 minutes.
- A metal electrode (Au, etc.) is thermally deposited on the hole transport layer.
- The solar cell devices are stored in air with ~20% relative humidity to promote oxygen doping.
*For more details, see the following reference 3 and 4.
References
- 1) Organometal halide perovskites as visible-light sensitizers for photovoltaic cells
- 2) NREL solar cell efficiency chart
- 3) Additive-free, Cost-Effective Hole-Transporting Materials for Perovskite Solar Cells Based on Vinyl Triarylamines
- 4) Experimental investigation of additive free-low-cost vinyl triarylamines based hole transport material for FAPbI3-based perovskite solar cells to enhance efficiency and stability
- 5) An Alternative to Chlorobenzene as a Hole Transport Materials Solvent for High-Performance Perovskite Solar Cells