and -emitting devices.22:T51e,Light-driven H₂ generation using semiconductor nanocrystal heterostructures has attracted intense recent interest because of the ability to rationally improve their performance by tailoring their size, composition, and morphology. In zero- and one-dimensional nanomaterials, the lifetime of the photoinduced charge-separated state is still too short for H₂ evolution reaction, limiting the solar-to-H₂ conversion efficiency. Here we report that using two-dimensional (2D) CdS nanoplatelet (NPL)-Pt heterostructures, H₂ generation internal quantum efficiency (IQE) can exceed 40% at pH 8.8-13 and approach unity at pH 14.7. The near unity IQE at pH 14.7 is similar to those reported for 1D nanorods and can be attributed to the irreversible hole removal by OH^-. At pH < 13, the IQE of 2D NPL-Pt is significantly higher than those in 1D nanorods. Detailed time-resolved spectroscopic studies and modeling of the elementary charge separation and recombination processes show that, compared to 1D nanorods, 2D morphology extends charge-separated state lifetime and may play a dominant role in enhancing the H₂ generation efficiency. This work provides a new approach for designing nanostructures for efficient light-driven H₂ generation.23:T4da,CsPbI₃ perovskite quantum dots (QDs) have shown great potential in light-harvesting and light-emitting applications, which often involve the transfer of charge carriers in and out of these materials. Here, we studied size-dependent charge separation (CS) and charge recombination (CR) between CsPbI₃ QDs and rhodamine B (RhB) molecules, using transient absorption spectroscopy. When the average size decreases from 11.8 nm to 6.5 nm, the average intrinsic CS time constant decreases from 872 ± 52 ps to 40.6 ± 4.3 ps and the corresponding charge recombination time constant decreases from 3829 ± 51 ns to 1384 ± 54 ns. The observed trend of size-dependent CS and CR rates can be well explained by Marcus theory using the theoretically calculated CS and CR driving forces (ΔG_CS and ΔG_CR), molecular reorganization energy (λ_RhB), and electronic coupling strength between QD and RhB (H_CS and H_CR). Unlike the extensively studied more strongly quantum confined Cd chalcogenide QDs, the CsPbI₃ QDs are in a weak quantum confinement regime in which size-dependent coupling strength plays a dominant role in the size-dependent charge transfer properties.24:T480,CsPbI3 perovskite quantum dot (QD) solar cells are a promising device platform for further development due to their improved stability compared to bulk materials. The fabrication of these devices often involves postsynthetic washing of colloidal QDs to remove surface ligands. Herein, we investigate how this postsynthetic treatment affects the charge separation (CS) and charge recombination (CR) processes at the interface of CsPbI3 QDs and the TiO2 electron extraction layer. The CS time constant at QD/TiO2 interface decrease from 457 ± 4 ps for QDs directly deposited on TiO2 to 288 ± 1 ps for QDs that were washed twice by methyl acetate, increasing the ET efficiency from 89.9 ± 0.3% to 98.3 ± 0.01%. Interestingly, this treatment also lengthens the average charge recombination time constants from 346 ± 18 ns to 1180 ± 60 ns, which is also beneficial for reducing charge recombination loss. This result demonstrates the pronounced effect of QD washing by methyl acetate (MeOAc) on interfacial charge transfer processes, suggesting the important effect of postsynthesis modification of colloidal perovskite QDs on solar cell efficiencies.

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1	Engineering	2	2	585
2	Applied Physics	2	2	585
3	Chemistry	2	2	585
4	Materials Science	2	2	585
5	Natural Sciences	1	1	562

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