High-Performance and Large-Area Inverted Perovskite Solar Cells Based on NiO_(x) Films Enabled with A Novel Microstructure-Control Technology

The improvement in the efficiency of inverted perovskite solar cells(PSCs)is significantly limited by undesirable contact at the NiO_(x)/perovskite interface.In this study,a novel microstructure-control technology is proposed for fabrication of porous NiO_(x)films using Pluronic P123 as the structure-directing agent and acetylacetone(AcAc)as the coordination agent.The synthesized porous NiO_(x)films enhanced the hole extraction efficiency and reduced recombination defects at the NiO_(x)/perovskite interface.Consequently,without any modification,the power conversion efficiency(PCE)of the PSC with MAPbl_(3)as the absorber layer improved from 16.50%to 19.08%.Moreover,the PCE of the device composed of perovskite Cs0.05(MA_(0.15)FA_(0.85))_(0.95)Pb(I_(0.85)Br_(0.15))_(3)improved from 17.49%to 21.42%.Furthermore,the application of the fabricated porous NiO_(x)on fluorine-doped tin oxide(FTO)substrates enabled the fabrication of large-area PSCs(1.2 cm^(2))with a PCE of 19.63%.This study provides a novel strategy for improving the contact at the NiO_(x)/perovskite interface for the fabrication of high-performance large-area perovskite solar cells.

Residual solvent extraction via chemical displacement for efficient and stable perovskite solar cells

Solvent residue is inevitable to occur in solution processed thin films,but its influence on the thin film quality has not been identified and addressed to date.Methylammonium acetate(MAAc)ionic liquid has recently been realized as an environmentally friendly solvent for solution processed perovskites.The specific high viscosity,low vapor pressure and strong association with perovskite precursor of the MAAc solvent is a double-edged sword,which endowed an advantageously ambient air operational and anti-solvent free perovskite deposition,but the MAAc is likely to be retained within the film and bring in detrimental effects on device performance of the corresponding solar cells.Herein,we reported a novel route to eliminate the residual solvent via a facial hydrochloric acid(HCl)annealing post-treatment(HAAP).In particular,chemical displacement reaction between the incorporated HCl and residual MAAc can be initiated to form volatile MACl and HAc,efficiently extracting MAAc residue.In the meanwhile,the stimulated mass transport via downward penetration and upward escape can trigger secondary perovskite growth with enlarged grain size and smoothened surface,leading to reduced defect state and improved interfacial contact intimacy,and also partial chloride ions are able to enter the crystal lattice to stabilize perovskite phase structure.As a result,a champion efficiency up to20.78%originating from enhanced Voc was achieved,and more than 96%of its initial efficiency can be maintained after 1000 h shelf-storage.

Stability of mixed-halide wide bandgap perovskite solar cells: Strategies and progress

Benefiting from the superior optoelectronic properties and low-cost manufacturing techniques,mixedhalide wide bandgap(WBG)perovskite solar cells(PSCs)are currently considered as ideal top cells for fabricating multi-junction or tandem solar cells,which are designed to beyond the Shockley-Queisser(S-Q)limit of single-junction solar cells.However,the poor long-term operational stability of WBG PSCs limits their further employment and hinders the marketization of multi-junction or tandem solar cells.In this review,recent progresses on improving environmental stability of mixed-halide WBG PSCs through different strategies,including compositional engineering,additive engineering,interface engineering,and other strategies,are summarized.Then,the outlook and potential direction are discussed and explored to promote the further development of WBG PSCs and their applications in multijunction or tandem solar cells.

Chiral cation promoted interfacial charge extraction for efficient tin-based perovskite solar cells

Pb-free Sn-based perovskite solar cells(PSCs) have recently made inspiring progress, and power conversion efficiency(PCE) of 14.8% has been achieved. However, due to the energy-level mismatch and poor interfacial contact between commonly used hole transport layer(i.e., poly(3,4-ethylenedioxythio phene):poly(styrene sulfonate), PEDOT:PSS) and FASnI_(3) film, it is still challenging to effectively extract holes at the interface. Owing to the p-type nature of Sn-based perovskites, the efficient hole extraction is of particular significance to improve the PCE of their solar cells. In this work, for the first time, the role of chiral cations, a-methylbenzylamine(S-/R-/rac-MBA), in promoting hole transportation of FASnI_(3)-based PSCs is demonstrated. The introduction of MBAs is found to form 2D/3D film with lowdimensional structures locating at PEDOT:PSS/FASnI_(3) interface, which facilitates the energy level alignment and efficient charge transfer at the interface. Importantly, chiral-induced spin selectivity(CISS)effect of R-MBA_(2)SnI_(4)induced by chiral R-MBA cation is found to further assist the specific interfacial transport of accumulated holes. As a result, R-MBA-based PSCs achieve decent PCE of 10.73% with much suppressed hysteresis and enhanced device stability. This work opens up a new strategy to efficiently promote the interfacial extraction of accumulated charges in working PSCs.

Stable Metal–Halide Perovskite Colloids in Protic Ionic Liquid

Obtaining long-term stable and robust perovskite colloids solution remains an important scientific challenge due to the limited interaction between solvent and perovskite solutes.Here,we unveil the formation mechanism of chemically robust perovskite precursor solutions under ambient conditions using methylammonium acetate(CH3NH3•CH3COO,MAAc)protic ionic liquid(PIL)solvent.Tens of nanometers colloids are assembled on the molecular level via regular oriented gel-like lamellae with a mean thickness of 34.69 nm,width of 56.81 nm,and distance of 91.05 nm.