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The two-step spin coating process produces rough perovskite surfaces in ambient condition with high humidity, which are unfavorable for the contact between the perovskite film and the low temperature carbon electrode. To tackle this problem, multi-walled carbon nanotubes (MWCNTs) are embedded into the perovskite layer. The MWCNTs can act as charge transport high way between individual perovskite nanoparticles and facilitate the collection of the photo-generated holes by the carbon electrode. Longer carrier lifetime is confirmed in the perovskite solar cells with addition of MWCNTs using open circuit voltage decay measurement. Under optimized concentration of MWCNT, average power conversion efficiency of 11.6% is obtained in hole transport material free perovskite solar cells, which is boosted by ∼15% compared to solar cells without MWCNT.

A mesoporous SiO2 layer is successfully introduced into the hole transport material free perovskite solar cells by spin-coating a SiO2 paste onto the TiO2 scaffold layer. This SiO2 layer can act as an insulating layer and effectively inhibit the charge recombination between the TiO2 layer and carbon electrode. The variation of power conversion efficiencies with the thickness of SiO2 layer is studied here. Under optimized SiO2 thickness, perovskite solar cell fabricated on the TiO2/SiO2 film shows a superior power conversion efficiency of ∼12% and exhibits excellent long time stability for 30 days.

Two dimensional materials have promising benefits in photoelectronic devices, including facilitating charge transport and reducing defects in perovskite solar cells (PSCs) and photodetectors (PDs) through interface engineering. Herein, a two dimension polymeric material of graphitic carbon nitride quantum dots (g-CNQDs) interlayer is used to modify the SnO2/perovskite interface in both ambient PSCs and PDs to improve the overall performance. The introduction of g-CNQD layer improves the crystalline quality of sequential perovskite absorber with high phase purity, less grain boundaries, low trap states and suppressed carrier recombination due to the intrinsic cross-linkable feature and relatively smooth surface of g-CNQD. As a result, with optimal modification, fully air-processed PSC reached a champion power conversion efficiency of 21.23% with negligible hysteresis, and the PDs had remarkable performance enhancement. Moreover, our PSCs have good stability in ambient air, keeping over 90% of the initial efficiency after 30 days’ exposure.

Stable hosts containing pre-stored metallic lithium (Li) are typically used to tackle irregular dendrite formation and infinite relative volume changes of lithium metal anodes. In this sense, oversimplified molten Li infusion strategies have been widely proposed to build lithiophilic architectures with uncontrollable amount and configuration of metallic Li in obtained hosts. In this work, tin oxide (SnO2) deposited Ni foam (SNF) with superior molten Li wettability is employed to construct two distinct lithiophilic architectures namely, Li coated SNF skeletons and Li infiltrated SNF frameworks. The cycling stability and dendritic behavior of these lithiophilic architectures are systematically compared. Both of these lithiophilic architectures significantly outperformed bare Li foils in terms of cycling performance and electrode dimension stability. The fully covered lithiophilic host with Li infiltrated SNF frameworks shows much better cycling stability and lower hysteresis than the porous lithiophilic host with Li coated skeletons, especially at high current densities and large stripping/plating capacities. In full-cell configurations, the batteries based on Li infiltrated SNF frameworks also show significantly higher rate capabilities than Li coated SNF skeletons counterpart. Our results provide a better understanding to design stable lithiophilic hosts for high-rate and high-capacity lithium metal anodes.

Liquid electrolytes employing fluorescent perylene are prepared and applied in dye sensitized solar cells (DSSCs). Due to the excellent down-shifting property of perylene, photons with short wavelength (from about 350 to 440 nm) can be absorbed and then converted to ones with longer wavelength (from 450 nm to 550 nm) which can be more efficiently utilized by DSSCs. As a result, device with optimal concentration of 0.05 M perylene presents an efficient improvement in the short-circuit current density ( J sc ), leading to an increase of 11.6% in the power conversion efficiency (PCE) compared with the reference DSSC based on control electrolyte.