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.

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.

Brazing diamond grits onto AA7075 aluminium alloy substrate with Ag–Cu–Ti filler alloy by laser heating

The brazing of diamond is a promising way to fabricate grinding wheels for efficient machining and precision grinding.This work investigated the feasibility of bonding diamond grits onto Aluminium Alloy 7075(AA7075)substrate with a Ag–Cu–Ti filler alloy via laser fusion brazing.The interfacial microstructures and the strength of the brazed diamond joints were studied.The cross-section of the brazed diamond joint consists of a molten filler alloy layer,a molten pool,a heat effect zone,a columnar crystal zone and an equiaxed crystal zone.Within the interface of the filler alloy/substrate metal,microstructures observed possibly were Ag(s.s),Al(s.s),Tix Al,Al2 Cu and Mg intermetallic compounds.A layer of Ti C with a thickness of about 30–50 nm was found at the bonding interface of the diamond/filler alloy.The averaged peak shear force of the brazed joints was found to be approximately 39.8 N.The abrasion grinding test indicated that the diamond/AA7075 brazed joint was adequate for grinding.However,the pulled-off of grit was found to be the primary failure of this type of brazed joint.This work broadened the brazing diamond technique and the range of applications of brazed diamond wheels for efficient grinding.