Blade-coating Perovskite Films with Diverse Compositions for Efficient Photovoltaics

In this research highlight,recent significant advances with hot-assisted blade-coating or air knife-assisted blade-coating of different perovskite compositions with bandgaps ranging from 1.3 eV to 1.9 eV(i.e.widebandgap or small-bandgap perovskites with mixed cations and anions,2D/3D perovskites,Pb/Sn binary perovskites,and all-inorganic perovskites)for single-junction or tandem PSCs are discussed,with an emphasis on elucidating the distinct ink formulation engineering strategies,crystal growth mechanisms,crystallization kinetics,and optoelectronic properties of the different perovskite compositions.

Layered-stacking of titania films for solar energy conversion:Toward tailored optical,electronic and photovoltaic performance

Nanostructured TiO2 with differentiate morphologies has attracted tremendous attention due to its wide band-gap nature as well as outstanding optical and electric properties for solar-driven light-toelectricity conversion application. Layered-stacking TiO2 film such as double-layer, tri-layer, quadrupleor quintuplicate-layer, is highly desirable to the design of high-performance semiconductor material photoanodes and the development of advanced photovoltaic devices. In this minireview, we will summarize the recent progress and achievements on proof-of-concept of layered-stacking TiO2 films（LTFs） for solar cells with emphasis on the tailored properties and synergistic functionalization of LTFs, such as optimized sensitizer adsorption, broadened light confinement as well as facilitated electron transport characteristics.Various demonstrations of LTFs photovoltaic systems provide lots of possibilities and flexibilities for more efficient solar energy utilization that a wide variety of TiO2 with distinguished morphologies can be integrated into differently structured photoanodes with synergistic and complementary advantages. This key structure engineering technology will also pave the way for the development of next generation state-ofthe-art electronics and optoelectronics. Finally, from our point of view, we conclude the future research interest and efforts for constructing more efficient LTFs as photoelectrode, which will be highly warranted to advance the solar energy conversion process.

Can the efficiencies of simplified perovskite solar cells go higher?

In recent years, metal halide perovskites have emerged as star semiconducting materials in the field of optoelectronic devices owing to their fascinating optoelectronic properties. Of particular interest are perovskite solar cells (PSCs), which have witnessed skyrocketing power conversion efficiencies (PCEs) within a short period of time, and were recently certified to reach 25.5%, which is already higher than other thin film photovoltaic technologies[1]. Nevertheless, multiple layers are still needed for state-of-theart PSCs to achieve high PCEs over 21%.

Intermarriage between amorphous and polycrystalline materials in perovskite solar cells:positive or not?

In recent few years,the research field of perovskite solar cells(PSCs)has witnessed an unprecedentedly rapid advancement in terms of skyrocketed power conversion efficiencies(PCEs)owing to the appealing optoelectronic properties of magic metal halide perovskite(MHP)materials,such as high absorption coefficient.

Amines modulation and passivation yields record perovskite optoelectronic devices

Perovskite-based optoelectronic devices using organic–inorganic, metal halide, hybrid thin films have revolutionized the pathway towards constructing more efficient and stable photovoltaics and light-emitting electronics [1,2]. Nevertheless, solutionprocessed polycrystalline perovskite films inevitably contain a high density of crystallographic or ionic defects.

Perovskite films with gradient bandgap for self-powered multiband photodetectors and spectrometers

Bandgap-graded materials present varying spectral responses at different positions,making them possible to be used as an alternative to photoactive materials array in multi-spectral responsive devices,thus miniaturizing the apparatus.However,the preparation of bandgap-graded materials usually requires complicated deposition process.Here we report a facile lowtemperature solution process to make films with lateral bandgap gradients,which form spontaneously via self-spreading and interdiffusion of solutions.We show lead halide perovskite films with MAPbCl_(3)-MAPbBr_(3)and MAPbBr_(3)-MAPbI_(3)gradients,which exhibit light absorption onsets ranging from 410 to 781 nm.The bandgap-graded films were used to make self-powered multiband photodetectors,which show different spectral responses at different positions without applying bias voltage.Furthermore,self-powered spectrometers were made by using the multiband photodetectors.

Chemical Linkage and Passivation at Buried Interface for Thermally Stable Inverted Perovskite Solar Cells with Efficiency over 22%

Poly[bis(4-phenyl)-(2,4,6-trimethylphenyl)amine](PTAA)has been developed as one of the most popular hole transport layer(HTL)materials in inverted perovskite solar cells(PSCs).However,the efficiency,thermal stability,and reproducibility of PTAA-based devices are still largely limited by underoptimized chemical interaction,energy level alignment,and contact affinity at the PTAA/perovskite interface.To this end,we introduced a bilateral chemical linker to simultaneously achieve favorable chemical interaction with the PTAA underlayer and form robust coordination bonding with the buried perovskite bottom layer,which beneficially improved the contact affinity,facilitated the hole extraction,well-passivated the interfacial defects,and relieved the nonradiative charge recombination at the HTL/perovskite buried interface.The inverted PSCs modified with interfacial chemical linker exhibited consistently higher power conversion efficiencies and performance reproducibility than that of the PTAA-only devices.Combined with the blade-coated FA0.4MA0.6PbI3 perovskite layer,a champion efficiency of 22.23%has been achieved,which is one of the highest reported values for the inverted PSCs based on the bilayer HTL.The targeted device showed enhanced thermal stability under continuous heating at 85℃ owing to suppressed composition segregation with robust interfacial linkage and consolidation.This work offers a new insight towards making efficient,thermally stable,and reproducible perovskite photovoltaics.

Perovskite-based tandem solar cells

The power conversion efficiency for single-junction solar cells is limited by the Shockley-Quiesser limit.An effective approach to realize high efficiency is to develop multi-junction cells.These years have witnessed the rapid development of organic–inorganic perovskite solar cells.The excellent optoelectronic properties and tunable bandgaps of perovskite materials make them potential candidates for developing tandem solar cells,by combining with silicon,Cu(In,Ga)Se_(2)and organic solar cells.In this review,we present the recent progress of perovskite-based tandem solar cells,including perovskite/silicon,perovskite/perovskite,perovskite/Cu(In,Ga)Se_(2),and perovskite/organic cells.Finally,the challenges and opportunities for perovskite-based tandem solar cells are discussed.

Air-stable Sn-based perovskite solar modules

All-perovskite tandem integrated photovoltaics (APTI-PVs),which maximize the light-harvesting in full-wavelength spectral range and combine the fascinating advantages of low-cost, solution-processability, and high-performance, are regarded as one of the most promising solutions for new-generation PV technology[1]. Encouragingly, the power conversion efficiency (PCE) of twoterminal APTI-PV device now has been surpassed the single-junction PSCs and reached a high level of exceeding 28%[2].

Custom Molecular Design of Ligands for Perovskite Photovoltaics

CONSPECTUS:Perovskite photovoltaics have witnessed overwhelming success owing to their high power conversion efficiency,low voltage deficit,sensitive photoelectric response and good operational stability.However,solution-processed,polycrystalline perovskite films inevitably contain a high density of crystallographic defects,such as uncoordinated ions and dangling bonds at the surfaces and grain boundaries,which can result in charge recombination,thus causing energy loss and impaired device performance.These intrinsic imperfections can be remedied through a chemically induced intermarriage between halide perovskites of soft crystallographic nature and judiciously designed exotic ligand molecules.Utilizing rational molecular design of the component moieties,i.e.,the core and tail functional groups,the ligand molecules can be endowed with both more comprehensive and salient advantages to further boost device performance,thus setting perovskite photovoltaics on course for a more prosperous future.