Abstract
Fully inorganic CsPbI3 perovskite quantum dots (CsPbI3-PQDs) are known as the best-performing photovoltaic absorber in colloidal quantum dot solar cells. This is achieved by improving the cubic-phase-stabilization and electronic-coupling in CsPbI3-PQD solids. In conventional approaches, the hydrolysis of methyl acetate (MeOAc) resulting in acetic acid and methanol as intermediate substances plays a key role in replacing long-chain hydrocarbons with short-chain ligands, which improves charge transport in the CsPbI3-PQD solids. However, CsPbI3-PQDs suffer from lattice distortion and instability under acidic conditions including protons and polar media, leading to CsPbI3-PQD fusion and poor photovoltaic performance. Herein, we report that electronic coupling and photovoltaic performance of CsPbI3-PQD solids are improved by efficient removal of long-chain oleate ligands using a solution of sodium acetate (NaOAc) in MeOAc, which results in the direct generation of OAc ions without forming protons and methanol. NaOAc-based ligand exchange of CsPbI3-PQDs enables preservation of their nanocrystal size without fusion and minimization of surface trap states originating from metal hydroxide formation on their surfaces. Consequently, the best solar cell comprising NaOAc-treated CsPbI3-PQDs shows an improved device performance with a power conversion efficiency (PCE) of 13.3%, as compared with a lead nitrate-treated control device (12.4% PCE).
Original language | English |
---|---|
Article number | 104130 |
Journal | Nano Energy |
Volume | 66 |
DOIs | |
State | Published - Dec 2019 |
Externally published | Yes |
Keywords
- Colloidal quantum dots
- CsPbI perovskites
- Sodium acetate
- Solar cells
- Solids-state ligand exchange