25%-Efficiency flexible perovskite solar cells via controllable growth of SnO_(2)

High power conversion efficiency(PCE)flexible perovskite solar cells(FPSCs)are highly desired power sources for aerospace crafts and flexible electronics.However,their PCEs still lag far behind their rigid counterparts.Herein,we report a high PCE FPSC by controllable growth of a SnO_(2)electron transport layer through constant pH chemical bath deposition(CBD).The application of SnSO_(4)as tin source enables us to perform CBD without strong acid,which in turn makes it applicable to acid-sensitive flexible indium tin oxide.Furthermore,a mild and controllable growth environment leads to uniform particle growth and dense SnO_(2)deposition with full coverage and reproducibility,resulting in a record PCE of up to 25.09%(certified 24.90%)for FPSCs to date.The as-fabricated FPSCs exhibited high durability,maintaining over 90% of their initial PCE after 10000 bending cycles.

Banana-shaped electron acceptors with an electron-rich core fragment and 3D packing capability

The emergence of Y6-type nonfullerene acceptors has greatly enhanced the power conversion efficiency(PCE)of organic solar cells(OSCs).However,which structural feature is responsible for the excellent photovoltaic performance is still under debate.In this study,two Y6-like acceptors BDOTP-1 and BDOTP-2 were designed.Different from previous Y6-type acceptors featuring an A–D–Aʹ–D–A structure,BDOTP-1,and BDOTP-2 have no electron-deficient Aʹfragment in the core unit.Instead,there is an electron-rich dibenzodioxine fragment in the core.Although this modification leads to a marked change in the molecular dipole moment,electrostatic potential,frontier orbitals,and energy levels,BDOTP acceptors retain similar three-dimensional packing capability as Y6-type acceptors due to the similar banana-shaped molecular configuration.BDOTP acceptors show good performance in OSCs.High PCEs of up to 18.51%(certified 17.9%)are achieved.This study suggests that the banana-shaped configuration instead of the A–D–Aʹ–D–A structure is likely to be the determining factor in realizing high photovoltaic performance.

Crystallization and Orientation Modulation Enable Highly Efficient Doctor-Bladed Perovskite Solar Cells

With the rapid rise in perovskite solar cells(PSCs)performance,it is imperative to develop scalable fabrication techniques to accelerate potential commercialization.However,the power conversion efficiencies(PCEs)of PSCs fabricated via scalable two-step sequential deposition lag far behind the state-of-the-art spin-coated ones.Herein,the additive methylammonium chloride(MACl)is introduced to modulate the crystallization and orientation of a two-step sequential doctorbladed perovskite film in ambient conditions.MACl can significantly improve perovskite film quality and increase grain size and crystallinity,thus decreasing trap density and suppressing nonradiative recombination.Meanwhile,MACl also promotes the preferred face-up orientation of the(100)plane of perovskite film,which is more conducive to the transport and collection of carriers,thereby significantly improving the fill factor.As a result,a champion PCE of 23.14%and excellent longterm stability are achieved for PSCs based on the structure of ITO/SnO_(2)/FA_(1-x)MA_xPb(I_(1-y)Br_y)_3/Spiro-OMeTAD/Ag.The superior PCEs of 21.20%and 17.54%are achieved for 1.03 cm~2 PSC and 10.93 cm~2 mini-module,respectively.These results represent substantial progress in large-scale two-step sequential deposition of high-performance PSCs for practical applications.

Double Layer Composite Electrode Strategy for Efficient Perovskite Solar Cells with Excellent Reverse-Bias Stability

Perovskite solar cells(PSCs)have become the represent-atives of next generation of photovoltaics;nevertheless,their stability is insufficient for large scale deployment,particularly the reverse bias stability.Here,we propose a transparent conducting oxide(TCO)and low-cost metal composite electrode to improve the stability of PSCs without sacrificing the efficiency.The TCO can block ion migrations and chemical reactions between the metal and perovskite,while the metal greatly enhances the conductivity of the composite electrode.As a result,composite electrode-PSCs achieved a power conversion efficiency(PCE)of 23.7%(certified 23.2%)and exhibited excellent stability,maintaining 95%of the initial PCE when applying a reverse bias of 4.0 V for 60 s and over 92%of the initial PCE after 1000 h continuous light soaking.This composite electrode strategy can be extended to different combinations of TCOs and metals.It opens a new avenue for improving the stability of PSCs.

4‑Terminal Inorganic Perovskite/Organic Tandem Solar Cells Offer 22%Efficiency

After fast developing of single-junction perovskite solar cells and organic solar cells in the past 10 years,it is becoming harder and harder to improve their power conversion efficiencies.Tandem solar cells are receiving more and more attention because they have much higher theoretical efficiency than single-junction solar cells.Good device performance has been achieved for perovskite/silicon and perovskite/perovskite tandem solar cells,including 2-terminal and 4-terminal structures.However,very few studies have been done about 4-terminal inorganic perovskite/organic tandem solar cells.In this work,semi-transparent inorganic perovskite solar cells and organic solar cells are used to fabricate 4-terminal inorganic perovskite/organic tandem solar cells,achieving a power conversion efficiency of 21.25%for the tandem cells with spin-coated perovskite layer.By using drop-coating instead of spin-coating to make the inorganic perovskite films,4-terminal tandem cells with an efficiency of 22.34%are made.The efficiency is higher than the reported 2-terminal and 4-terminal inorganic perovskite/organic tandem solar cells.In addition,equivalent 2-terminal tandem solar cells were fabricated by connecting the sub-cells in series.The stability of organic solar cells under continuous illumination is improved by using semi-transparent perovskite solar cells as filter.

A chlorinated lactone polymer donor featuring high performance and low cost

The development of low-bandgap nonfullerene acceptors and wide-bandgap polymer donors speeds up the advance of organic solar cells(OSCs)[1-17]. Wide-bandgap copolymers based on fused-ring acceptor units are ideal donor materials due to their low-lying HOMO levels, high hole mobilities and complementary light absorption to nonfullerene acceptors[18-25]. Currently, high-performance donors with 18%power conversion efficiencies(PCEs) belong to this type.

Applications of vacuum vapor deposition for perovskite solar cells:A progress review

Metal halide perovskite solar cells(PSCs)have made substantial progress in power conversion efficiency(PCE)and stability in the past decade thanks to the advancements in perovskite deposition methodology,charge transport layer(CTL)optimization,and encapsulation technology.Solution-based methods have been intensively investigated and a 25.7% certified efficiency has been achieved.Vacuum vapor deposition protocols were less studied,but have nevertheless received increasing attention from industry and academia due to the great potential for large-area module fabrication,facile integration with tandem solar cell architectures,and compatibility with industrial manufacturing approaches.In this article,we systematically discuss the applications of several promising vacuum vapor deposition techniques,namely thermal evaporation,chemical vapor deposition(CVD),atomic layer deposition(ALD),magnetron sputtering,pulsed laser deposition(PLD),and electron beam evaporation(e-beam evaporation)in the fabrication of CTLs,perovskite absorbers,encapsulants,and connection layers for monolithic tandem solar cells.

Major strategies for improving the performance of perovskite solar cells

Metal halide perovskite solar cell(PSC)has successfully distinguished itself in optoelectronic field by virtue of the sharp rise in power conversion efficiency over the past decade.The remarkable efficiency breakthrough at such a fast speed can be mainly attributed to the comprehensive study on film deposition techniques,especially the effective management of surface and interfacial defects in recent works.Herein,we summarized the current trends in performance enhancement for PSCs,with a focus on the generally applicable strategies in high-performance works,involving deposition methods,compositional engineering,additive engineering,crystallization manipulation,charge transport material selection,interfacial passivation,optical coupling effect and constructing tandem solar cells.Promising directions and perspectives are also provided.

Brominated PEAI as Multi-Functional Passivator for High-Efficiency Perovskite Solar Cell

The interfaces of perovskite solar cells(PSCs)are well known to be rich in deep-level carrier traps,which serve as non-radiative recombination centers and limit the open-circuit voltage(Voc)and power conversion efficiency(PCE)of PSCs.Defect chemistry and surface passivators have been researched extensively and mainly focused on the neutralization of uncoordinated lead or anion defects.Herein,a novel brominated passivator 2-bromophenethylammonium iodide(2-Br-PEAI)is introduced for a multi-functional passivation effect at the perovskite interface.The brominated species readily form 2D perovskite on top of the 3D perovskite and multi-interact with the 3D perovskite surface.Apart from the halide vacancy filling and anion bonding ability,the Br atoms on the benzene ring can interact with the FA cations via strong hydrogen bonding N-H…Br and interact with the[PbI_(6)]^(4−)inorganic framework.The interface defects in the PSCs are well passivated,minimizing non-radiative recombination and enhancing device performance.As a result,a champion PCE of 24.22%was achieved with high V_(oc)and fill factor.In addition,modified devices also showed enhanced operational stability(retention of>95%initial PCE after 400 h)and humidity resistance(>90%initial PCE maintained after 1500 h under~50%RH).

有机太阳电池关键材料研究进展

有机太阳电池具有质量轻、柔性、印刷制备等优点,有巨大的应用潜力,从其诞生那一刻起便引起了学术界和工业界的广泛研究兴趣.历经25年的发展,有机太阳电池效率已突破18%,其快速进步得益于不断涌现的高性能新材料和器件制备技术,以及对电池活性层形貌、分子堆积和器件机理的深入理解.基于有机共轭结构的电子给体和电子受体材料是决定有机太阳电池性能的关键材料.本文将以给、受体材料的发展历程为主线,聚焦那些明星材料和里程碑工作,阐述高性能关键材料的分子结构演变和进化过程,最后展望其面临的挑战和未来发展方向.

Progress of the key materials for organic solar cells

Organic solar cells have attracted academic and industrial interests due to the advantages like lightweight,flexibility and roll-to-roll fabrication.Nowadays,18%power conversion efficiency has been achieved in the state-of-the-art organic solar cells.The recent rapid progress in organic solar cells relies on the continuously emerging new materials and device fabrication technologies,and the deep understanding on film morphology,molecular packing and device physics.Donor and acceptor materials are the key materials for organic solar cells since they determine the device performance.The past 25 years have witnessed an odyssey in developing high-performance donors and acceptors.In this review,we focus on those star materials and milestone work,and introduce the molecular structure evolution of key materials.These key materials include homopolymer donors,D-A copolymer donors,A-D-A small molecular donors,fullerene acceptors and nonfullerene acceptors.At last,we outlook the challenges and very important directions in key materials development.

Over 16% efficiency from thick-film organic solar cells

近年来有机太阳电池效率突飞猛进,单结电池效率已经突破18%,然而这些高效率电池的活性层厚度通常只有100 nm左右,随着厚度增加,电池效率下降明显.为了实现有机太阳电池的产业化,发展对厚度不敏感,且可适用于卷对卷印刷制备的高性能厚膜电池势在必行.本文通过在D18:Y6二元活性层中加入少量富勒烯受体PC61BM,使得电池对厚度的敏感性显著降低. PC61BM的加入使厚膜活性层的电子和空穴迁移率明显提高,载流子传输更加平衡,并且显著降低了陷阱辅助复合.D18:Y6:PC61BM(1:1.6:0.2)三元电池在活性层厚度超过300 nm时,还能保持16%以上的效率,是目前性能最优异的厚膜有机太阳电池之一.

Interface engineering gifts CsPbI2.25Br0.75 solar cells high performance

Organic-inorganic halide perovskite (ABX3) solar cells (PSCs)have made great progress in recent years [1]. The power conversion efficiency (PCE) has increased up to 25.2%(NREL Best Research-Cell Efficiency Chart, https://www.nrel.gov/pv/cell-efficiency.html, Accessed August 2019). However, they suffer from poor thermal stability due to the volatile A-site organic cations.

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.

Multifunctional succinate additive for flexible perovskite solar cells with more than 23%power-conversion efficiency

Flexible perovskite solar cells(FPSCs)have emerged as power sources in versatile applications owing to their high-efficiency characteristics,excellent flexibility,and relatively lowcost.Nevertheless,undesired strain in perovskite films greatly impacts the power-conversion efficiency(PCE)and stability of PSCs,particularly in FPSCs.Herein,a novel multifunctional organic salt,methylammonium succinate,which can alleviate strain and reinforce grain boundaries,was incorporated into the perovskite film,leading to relaxed microstrain and a lower defect concentration.As a result,a PCE of 25.4%for rigid PSCs and a record PCE of 23.6%(certified 22.5%)for FPSCs have been achieved.In addition,the corresponding FPSCs exhibited excellent bending durability,maintaining
85%of their initial efficiency after bending at a 6 mm radius for 10000 cycles.