All-inorganic α-CsPbI 3 perovskite quantum dots (QDs) are attracting high interest as solar cell absorbers due to their appealing light harvesting properties and enhanced stability due to the absence of volatile organic constituents. Moreover, ex situ synthesized QDs significantly reduce the variability of the perovskite layer deposition process. However, it is highly challenging to incorporate α-CsPbI 3 QDs into mesoporous TiO 2 (m-TiO 2), which constitutes the best performing electron transport material in state-of-the-art perovskite solar cells. Herein, the m-TiO 2 surface is engineered using an electron-rich cesium-ion containing methyl acetate solution. As one effect of this treatment, the solid-liquid interfacial tension at the TiO 2 surface is reduced and the wettability is improved, facilitating the migration of the QDs into m-TiO 2. As a second effect Cs + ions passivate the QD surface and promote the charge transfer at the m-TiO 2 /QD interface, leading to an enhancement of the electron injection rate by a factor of three. In combination with an ethanol-environment smoothing route significantly reducing the surface roughness of the m-TiO 2 /QD layer, optimized devices exhibit highly reproducible power conversion efficiencies exceeding 13%. The best cell with an efficiency of 14.32% (reverse scan) reaches a short-circuit current density of 17.77 mA cm −2 , which is an outstanding value for QD-based perovskite solar cells.
Perovskite solar cells (PSCs) have developed rapidly in the past 10 years. However, they are faced with a huge challenge for stability improvement because of the volatile organic components in the light absorption and hole transporting layer. Herein, we fabricate all-inorganic PSCs with the structure of FTO/c-TiO 2 /m-TiO 2 /CsPbI 3 quantum dots (QDs)/Cu 12 Sb 4 S 13 QDs/Au to improve device stability. To enhance the photovoltaic performance of PSCs, the surface oleylamine ligands of Cu 12 Sb 4 S 13 QDs with 3-mercaptopropionic acid are exchanged, as the enhanced electronic coupling and reduced band gap are realized after the ligands exchange. Cu 12 Sb 4 S 13 QD based PSCs exhibit a PCE of 10.02%, approaching that of the spiro-MeOTAD based PSCs (12.14%). A high shortcircuit current density of 18.28 mA cm −2 is achieved because of the enhanced light absorption and excellent hole extraction ability of Cu 12 Sb 4 S 13 QDs. Moreover, Cu 12 Sb 4 S 13 QD based PSCs exhibit the improved long-term stability and retain 94% of their initial PCE after storage in ambient air for 360 h.
All-inorganic
CsPbI3 perovskite quantum dots (QDs) have
attracted great attention since emerging as a new class of materials
with superior light-harvesting properties and enhanced thermal stability
compared to organic–inorganic hybrid perovskites. However,
poor phase stability remains a bottleneck for practical applications.
In the present work, CsPb(I1–x
Br
x
)3 perovskite QDs are synthesized
by Br doping to increase the tolerance factor for the improvement
of phase stability, and the balance between the stability of solar
cells and the power conversion efficiency (PCE) is considered by adjusting
the Br doping content. It is found that the phase stability of CsPb(I1–x
Br
x
)3 QDs is much improved, while their band gap increases from
1.77 to 1.89 eV when the Br doping content increases from 0 to 30%.
CsPbI2.4Br0.6 QD-based perovskite solar cells
(PSCs) achieve a proper balance between high PCE and stability; the
PCE is 12.31%, approaching that of the CsPbI3-based PSCs
(14.13%), and may retain 87% of the initial efficiency after 15 days
of storage in ambient air.
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