Efficient Semi‑Transparent Wide‑Bandgap Perovskite Solar Cells Enabled by Pure‑Chloride 2D‑Perovskite Passivation

Wide-bandgap(WBG)perovskite solar cells suffer from severe non-radiative recombination and exhibit relatively large opencircuit voltage(V_(OC))deficits,limiting their photovoltaic performance.Here,we address these issues by in-situ forming a well-defined 2D perovskite(PMA)_(2)PbCl_(4)(phenmethylammonium is referred to as PMA)passivation layer on top of the WBG active layer.The 2D layer with highly pure dimensionality and halide components is realized by intentionally tailoring the side-chain substituent at the aryl ring of the post-treatment reagent.First-principle calculation and single-crystal X-ray diffraction results reveal that weak intermolecular interactions between bulky PMA cations and relatively low cation-halide hydrogen bonding strength are crucial in forming the well-defined 2D phase.The(PMA)_(2)PbCl_(4)forms improved type-I energy level alignment with the WBG perovskite,reducing the electron recombination at the perovskite/hole-transport-layer interface.Applying this strategy in fabricating semi-transparent WBG perovskite solar cells(indium tin oxide as the back electrode),the V_(OC)deficits can be reduced to 0.49 V,comparable with the reported state-of-the-art WBG perovskite solar cells using metal electrodes.Consequently,we obtain hysteresis-free 18.60%-efficient WBG perovskite solar cells with a high V_(OC)of 1.23 V.

Discovery of pockmarks in the Zengmu Basin,southern South China Sea and the implication

The Zengmu Basin located in the shallow water area of the southern South China Sea,is rich in oil and gas resources,within which faults and mud-diapir are developed,but it is unknown whether oil and gas migrate to the seafloor surface.The newly collected multibeam data across the Zengmu Basin reveal a large number of depressions,with depths of 2-4 m,widths of several tens of meters,large distribution range of 1.8-8 km along survey line,up to~50 km,and their backscatter intensity(-26 dB)is much greater than that of the surrounding area(-38 dB).Combined with the developed mud-diapir and fracture structures,and abundant oil and gas resources within this basin,these depressions are presumed to be pockmarks.Furthermore,more than 110 mono-sized small circular pockmarks,with a depth of less than 1 m and a width of 5 m,are observed in an area of less than 0.03 km2,which are not obliterated by sediment infilling with high sedimentation rate,implying an existence of unit-pockmarks that are or recently were active.In addition,seismic profiles across the Zengmu Basin show characterization of upward migration of hydrocarbons,expressed as mud-diapir structures,bright spots in the shallow formation with characteristics of“low frequency increase and high frequency attenuation”.The subbottom profiles show the mud-diapir structures,as well as the gas-bearing blank zones beneath the seafloor.These features suggest large gas leaking and occurrence of large amounts of carbonate nodules on the seafloor.This indicates the complex and variable substrate type in the Zengmu Basin,while the area was once thought to be mainly silty sand and find sand.This is the first report on the discovery of pockmarks in the Zengmu Basin;it will provide basic information for submarine stability and marine engineering in China’s maritime boundaries.

Sputtered SnO_(2)as an interlayer for efficient semitransparent perovskite solar cells

SnO_(2)is widely used as the electron transport layer(ETL)in perovskite solar cells(PSCs)due to its excellent electron mobility,low processing temperature,and low cost.And the most common way of preparing the SnO_(2)ETL is spincoating using the corresponding colloid solution.However,the spin-coated SnO_(2)layer is sometimes not so compact and contains pinholes,weakening the hole blocking capability.Here,a SnO_(2)thin film prepared through magnetron-sputtering was inserted between ITO and the spin-coated SnO_(2)acted as an interlayer.This strategy can combine the advantages of efficient electron extraction and hole blocking due to the high compactness of the sputtered film and the excellent electronic property of the spin-coated SnO_(2).Therefore,the recombination of photo-generated carriers at the interface is significantly reduced.As a result,the semitransparent perovskite solar cells(with a bandgap of 1.73 eV)based on this double-layered SnO_(2)demonstrate a maximum efficiency of 17.7%(stabilized at 17.04%)with negligible hysteresis.Moreover,the shelf stability of the device is also significantly improved,maintaining 95%of the initial efficiency after 800-hours of aging.

Sputtering under Mild Heating Enables High-Quality ITO for Efficient Semi-Transparent Perovskite Solar Cells

Semi-transparent perovskite solar cells(ST-PSCs)are promising in building-integrated photovoltaics(BIPVs)and tandem solar cells(TSCs).One of the keys to fabricate high-performance ST-PSCs is depositing efficient transparent electrodes.Indium tin oxide(ITO)is an excellent transparent conductive oxide with good light transmittance and high conductivity.However,the high sheet resistance of ITO sputtered at room temperature leads to the low fill factor(FF)and poor power conversion efficiency(PCE)of the ST-PSCs.Here,we study the effect of the sputtering temperature on the properties of ITO and the performance of ST-PSCs.We find that when the sputtering temperature increases from the room temperature to 70℃,the crystallinity of the sputtered ITO gradually improves.Therefore,the sheet resistance decreases and the corresponding device performance improves.However,once the sputtering temperature further increases over 70℃,the underlying hole transport layer will be damaged,leading to poor device performance.Therefore,the optimized mild heating temperature of 70℃is applied and we obtain ST-PSCs with a champion PCE of 15.21%.We believe this mild heating assisted sputtering method is applicable in fabricating BIPVs and TSCs.

Stabilizing semi-transparent perovskite solar cells with a polymer composite hole transport layer

Semi-transparent perovskite solar cells(ST-PSCs)have broad applications in building integrated photovoltaics.However,the stability of ST-PSCs needs to be improved,especially in n-i-p ST-PSCs since the doped 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene(Spiro-OMeTAD)is unstable at elevated temperatures and high humidity.In this work,aπ-conjugated polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)](PBDB-T)is selected to form a polymer composite hole transport layer(HTL)with Spiro-OMeTAD.The sulfur atom of the thiophene unit and the carbonyl group of the polymer interact with the undercoordinated Pb2+at the perovskite surface,which stabilizes the perovskite/HTL interface and passivates the interfacial defects.The incorporation of the polymer also increases the glass transition temperature and the moisture resistance of Spiro-OMeTAD.As a result,we obtain ST-PSCs with a champion efficiency of 13.71%and an average visible light transmittance of 36.04%.Therefore,a high light utilization efficiency of 4.94%can be obtained.Moreover,the encapsulated device can maintain 84%of the initial efficiency after 751 h under continuous one-sun illumination(at 30%relative humidity)at the open circuit and the unencapsulated device can maintain 80%of the initial efficiency after maximum power tracking for more than 1250 h under continuous one-sun illumination.

Electromechanical behavior of fiber-reinforced dielectric elastomer membrane

Based on its large deformation,light weight,and high energy density,dielectric elastomer(DE)has been used as driven muscle in many areas.We design the fiberreinforced DE membrane by adding fibers in the membrane.The deformation and driven force direction of the membrane can be tuned by changing the fiber arrangements.The actuation in the perpendicular direction of the DE membrane with long fibers first increases and then decreases by the increasing of the fiber spacing in the perpendicular direction.The horizontal actuation of the membrane decreases by decreasing the spacing of short fibers.In the membrane-inflating structure,the radially arranged fibers will break the axisymmetric behavior of the structure.The top area of the inflated balloon without fiber will buckle up when the voltage reaches a certain level.Finite element simulations based on nonlinear field theory are conducted to investigate the effects of fiber arrangement and verify the experimental results.This work can guide the design of fiber-reinforced DE.