Tin dioxide buffer layer-assisted efficiency and stability of wide-bandgap inverted perovskite solar cells

Inverted perovskite solar cells(IPSCs) have attracted tremendous research interest in recent years due to their applications in perovskite/silicon tandem solar cells. However, further performance improvements and long-term stability issues are the main obstacles that deeply hinder the development of devices. Herein, we demonstrate a facile atomic layer deposition(ALD) processed tin dioxide(SnO2) as an additional buffer layer for efficient and stable wide-bandgap IPSCs. The additional buffer layer increases the shunt resistance and reduces the reverse current saturation density, resulting in the enhancement of efficiency from 19.23% to 21.13%. The target device with a bandgap of 1.63 eV obtains open-circuit voltage of 1.19 V, short circuit current density of 21.86 mA/cm^(2), and fill factor of 81.07%. More importantly, the compact and stable SnO_(2) film invests the IPSCs with superhydrophobicity, thus significantly enhancing the moisture resistance. Eventually, the target device can maintain 90% of its initial efficiency after 600 h storage in ambient conditions with relative humidity of 20%–40% without encapsulation. The ALD-processed SnO_(2) provides a promising way to boost the efficiency and stability of IPSCs, and a great potential for perovskite-based tandem solar cells in the near future.

Enhanced efficiency and stability of triple-cation perovskite solar cells with CsPbI_(x)Br_(3−x)QDs“surface patches”

Perovskite solar cells(PSCs)with a light-harvesting three-dimensional perovskite bulk layer as backbone component have achieved great progress in performance.Nonradiative recombination is one major place to improve efficiency and stability as they cause significant energy loss in PSCs.Additionally,an imperfection in grain boundaries will initiate device degradation.One of the most successful strategies to decrease nonradiative recombination in PSCs is the introduction of reduced dimensional perovskite(e.g.,perovskite quantum wells),benefiting the device's efficiency and stability tremendously.Here,instead of quantum wells,mixed-cation perovskites with ligand-contained CsPbBr_(x)I_(3−x)quantum dots(QDs)are prepared,which is shown to function as perovskite healing“surface patches.”Benefiting from the“surface patches”effect,the QDs-film shows reduced defects and enhancing film quality which lead to the excellent performance of solar cells(enhancing the power conversion efficiency from 19.21%of the control device to 21.71%[22.1%in reverse scan]).

Recent Progress of Layered Perovskite Solar Cells Incorporating Aromatic Spacers

Layered two dimensional(2D) or quasi-2D perovskites are emerging photovoltaic materials due to their superior environment and structure stability in comparison with their 3D counterparts. The typical 2D perovskites can be obtained by cutting 3D perovskites along < 100 > orientation by incorporation of bulky organic spacers, which play a key role in the performance of 2D perovskite solar cells(PSCs). Compared with aliphatic spacers, aromatic spacers with high dielectric constant have the potential to decrease the dielectric and quantum confinement effect of 2D perovskites, promote efficient charge transport and reduce the exciton binding energy, all of which are beneficial for the photovoltaic performance of 2D PSCs. In this review, we aim to provide useful guidelines for the design of aromatic spacers for 2D perovskites. We systematically reviewed the recent progress of aromatic spacers used in 2D PSCs. Finally, we propose the possible design strategies for aromatic spacers that may lead to more efficient and stable 2D PSCs.

Homogeneous permeation and oriented crystallization in nanostructured mesopores for efficient and stable printable mesoscopic perovskite solar cells

The low-cost and scalable printable mesoporous perovskite solar cells(p-MPSCs) face significant challenges in regulating perovskite crystal growth due to their nanoscale mesoporous scaffold structure, which limits the improvement of device power conversion efficiency(PCE). In particular, the most commonly used solvents, N,N-dimethylformamide(DMF) and dimethyl sulfoxide(DMSO), have a single chemical interaction with the precursor components and high volatility, which is insufficient to self-regulate the perovskite crystallization process, leading to explosive nucleation and limited growth within mesoporous scaffolds. Here, we report a mixed solvent system composed of methylamine formaldehyde(MAFa)-based ionic liquid and acetonitrile(ACN) with the strong C=O–Pb coordination and N–H···I hydrogen bonding with perovskite components. We found that the mixed solvent system is beneficial for the precursor solution to homogeneously penetrate into the mesoporous scaffold,and the strong C=O–Pb coordination and N–H···I hydrogen bonding interaction can promote the oriented growth of perovskite crystals. This synergistic effect increased the PCE of the p-MPSCs from 17.50% to 19.21%, which is one of the highest records for p-MPSC in recent years. Additionally, the devices exhibit positive environmental stability, retaining over 90% of the original PCE after 1,200 h of aging under AM 1.5 illumination conditions at 55 ℃ and 55% humidity.

Rolling Partial Rescheduling with Dual Objectives for Single Machine Subject to Disruptions

This paper discusses the single-machine rescheduling problem with efficiency and stability as criteria, where more than one disruption arises in large-scale dynamic circumstances. Partial rescheduling (PR) strategy is adopted after each disruption and a rolling mechanism is driven by events in response to disruptions. Two kinds of objective functions are designed respectively for PR sub-problem involving in the interim and the terminal of unfinished jobs. The analytical result demonstrates that each local objective is consistent with the global one. Extensive computational experiment was performed and the computational results show that the rolling PR strategy with dual objectives can greatly improve schedule stability with little sacrifice in efficiency and provide a reasonable trade-off between solution quality and computational efforts.

Dual interfacial engineering for efficient Cs_(2)AgBiBr_(6) based solar cells

The emerging lead-free halide double perovskite solar cells have attracted widespread attentions due to their long-term stability and non-toxicity, but suffer from the low device performance. One efficiencylimiting factor is the improper contacts between the halide double perovskite and anode/cathode electrodes. Here, we improve the efficiency and stability of the bismuth-halide double perovskite based solar cells by a synergistic interface design for both electron and hole transport layers(ETL/HTL). The results show that the modification of the TiO_2 ETL with a thin hydrophobic C60 layer and replacement of the lithium-doped small molecule HTL with an un-doped conjugated polymer lead to higher surface quality of perovskite film and better energy-level alignment at the contacts. As a result, the optimized device shows reduced trap density, suppressed charge recombination and enhanced charge extraction, leading to an increase of 69% in device efficiency. In addition, the device also exhibits superior stability in ambient environment, heat stress and light bias after interface optimization. This work provides an efficient strategy for the device optimization of the emerging lead-free perovskite solar cells.

Reducing surficial and interfacial defects by thiocyanate ionic liquid additive and ammonium formate passivator for efficient and stable perovskite solar cells

Organic–inorganic metal halide perovskites have attained extensive attention owing to their outstanding photovoltaic performances,but the existence of numerous defects in crystalline perovskites is still a serious constraint for the further development of perovskite solar cells(PSCs).In particular,the rapid crystallization guided by anti-solvents leads to plenty of surficial and interfacial defects in perovskite films.Herein,we report the adoption of a pseudo-halide anion based ionic liquid additive,1-butyl-3-methylimidazolium thiocyanate(BMIMSCN)for growing ternary cation(CsFAMA,where FA=formamidinium and MA=methylammonium)perovskites with large-scale crystal grains and strong preferential orientation via the enhanced Ostwald ripening.Meanwhile,a novel halide-free passivator,benzylammonium formate(BAFa),was employed as a buffering layer on the perovskite films to suppress surface-dominated charge recombination.As a result,the cooperative effects of BMIMSCN additive and BAFa passivator lead to significant enhancements on fluorescence lifetime(from 79.41 to 201.01 ns),open-circuit voltage(from 1.13 to 1.19 V),photoelectric conversion efficiency(from 18.90%to 22.33%).Moreover,the BMIMSCN/BAFa-CsFAMA PSCs demonstrated greatly improved stability against moisture and heat.This work suggests a promising strategy to improve the quality of perovskite materials via reducing the surficial and interfacial defects by the synergistic effects of lattice doping and interface engineering.