Search

A solvent-free solid-phase technique was developed for the targeted defect passivation of perovskite films, resulting in an ultra-high PCE of 25.2%.

A pre-embedding mixed A-cation halide strategy is developed to eliminate the residual unstable PbI2 and lattice strain near the buried interface of the perovskite layer for the stability improvement of formamidinium-based perovskite solar cells.

Amines are widely employed as additives for improving the performance of metal halide perovskite optoelectronic devices. However, amines are well-known for their high chemical reactivity, the impact of which has yet to receive enough attention from the perovskite light-emitting diode community. Here, by investigating an unusual positive aging effect of CH3NH3I/CsI/PbI2 precursor solutions as an example, we reveal that amines gradually undergo N-formylation in perovskite precursors over time. This reaction is initialized by hydrolysis of dimethylformamide in the acidic chemical environment. Further investigations suggest that the reaction products collectively impact perovskite crystallization and eventually lead to significantly enhanced external quantum efficiency values, increasing from similar to 2% for fresh solutions to greater than or similar to 12% for aged ones. While this case study provides a positive aging effect, a negative aging effect is possible in other perovksite systems. Our findings pave the way for more reliable and reproducible device fabrication and call for further attention to underlying chemical reactions within the perovskite inks once amine additives are included. Funding Agencies|ERCEuropean Research Council (ERC)European Commission [717026]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [51472164, 62005126]; 1000 Talents Program for Young Scientists of China; Shenzhen Peacock Plan [KQTD2016053112042971]; Educational Commission of Guangdong Province [2015KGJHZ006]; Research Foundation-Flanders (FWO)FWO [12Y7221N]

Electron acceptors with a chemical structure of A–DA′D–A (in which A denotes an acceptor moiety and D a donor moiety) are rapidly gaining prominence in organic solar cells (OSCs). In OSCs containing these acceptors, record power conversion efficiencies (PCEs) exceeding 16% are now widely reported. Despite encouraging advances related to new material designs and PCEs, the fundamental interplay between molecular structure and device performance still requires further understanding. Here, we choose two model A–DA′D–A type acceptors, Y3 and Y18, that have almost identical structures, and examine how the presence of two extra alkyl chains (attached to the periphery of the DA′D core) in Y18 impacts on its solid state properties and device performance. These properties include: (i) charge transport; (ii) heat transfer; and (iii) electronic disorder. We found that bulk-heterojunction (BHJ) OSCs that use Y3 and Y18 have markedly different PCEs of ∼13 and 16%, respectively. Correspondingly, the BHJ containing Y18 possesses more efficient phonon transfer and charge transport and suppressed electronic disorder. Among these properties, the extremely low Urbach energy (EU) of 23 meV in Y18 stands out because this is even below the thermal energy (∼26 meV), which sets the electronic disorder limit at room temperature. With all these contrasting results, a simple molecular model can be rationalized in which the extra alkyl chains in Y18 help to suppress the formation of rotamers, endowing it with a disorder free molecular conformation and remarkable solid state properties. This work provides not only a new physical understanding of the effect of alkyl chains in organic semiconductors, but also new ideas for the synthesis of novel materials that can be adopted for use in high-performance OSCs.

Defects play an important role in the degradation processes of hybrid halide perovskite absorbers, impeding their application for solar cells. Among all defects, halide anion and organic cation vacancies are ubiquitous, promoting ion diffusion and leading to thin-film decomposition at surfaces and grain boundaries. Here, we employ fluoride to simultaneously passivate both anion and cation vacancies, by taking advantage of the extremely high electronegativity of fluoride. We obtain a power conversion efficiency of 21.46% (and a certified 21.3%-efficient cell) in a device based on the caesium, methylammonium (MA) and formamidinium (FA) triple-cation perovskite (Cs0.05FA0.54MA0.41)Pb(I0.98Br0.02)3 treated with sodium fluoride. The device retains 90% of its original power conversion efficiency after 1,000 h of operation at the maximum power point. With the help of first-principles density functional theory calculations, we argue that the fluoride ions suppress the formation of halide anion and organic cation vacancies, through a unique strengthening of the chemical bonds with the surrounding lead and organic cations. Defects and defect migration are detrimental for perovskite solar cell efficiency and long-term stability. Li et al. show that fluoride is able to suppress the formation of halide anion and organic cation vacancy defects by restraining the relative ions via ionic and hydrogen bonds.

Blending perovskite with different cations has been successful in improving performance of perovskite solar cells, but the complex pathway of perovskite crystal formation remains a mystery, hindering its further development. In this paper, the detailed crystallization process of formamidinium lead iodide (FAPbI3) perovskite films doped by methylammonium lead bromide (MAPbBr3) additive was investigated by in situ grazing incident wide-angle X-ray scattering measurements during both spin coating and annealing. During spin-coating, it was found that the FAPbI3 perovskite precursor easily formed a mixture of black perovskite phase (α phase) and non-perovskite yellow phase (δ phase) after the addition of MAPbBr3, whereas only δ phase formed without MAPbBr3. The δ phase gradually converted to α phase during annealing and there was only α phase left in both films with and without MAPbBr3. However, the doped films presented high film quality without PbI2 residue in contrast to the undoped films. These findings imply that the MAPbBr3 additive can effectively suppress the formation of the unfavorable δ phase and trigger the formation of the optically active α phase even during spin-coating, which enhances the film quality possibly by removing the energy barriers from δ phase to α phase at room temperature. Finally, PSCs based on MAPbBr3-doped FAPbI3 were fabricated with a champion efficiency as high as 19.4% from 14.2% for the PSCs based on undoped FAPbI3.

MgAl2O4:Cr3+ far-red emitting ceramic phosphors were prepared by the solid-state reaction method. The photoluminescence characteristics, especially the luminescence thermal stability, thermal conductivity, and its application in phosphor-converted LEDs were studied. Under 450 nm excitation, the ceramic phosphors exhibited an emission range of 650-750 nm and showed a narrow-band emission peaked at 688 nm. It also shows 708 nm and 718 nm far-red emission, which matches well with the absorption peak of the plant phytochrome PFR. The luminescence thermal stability of MgAl1.99O4:0.01Cr3+ was excellent. The integral intensity of the two emissions peaked at 708 nm and 718 nm at 500 K can maintain 98.27% and 98.24% of the counterparts measured at room temperature, respectively, showing zero thermal quenching behavior up to 500 K. The thermal conductivity of the MgAl1.99O4:0.01Cr3+ ceramic was 10.3 W·m-1·K-1. These results indicate that MgAl2O4:Cr3+ ceramic phosphors can be applied in plant lighting when packaged onto 450 nm blue LED chips.

Although perovskite light-emitting diodes (PeLEDs) have recently experienced significant progress, there are only scattered reports of PeLEDs with both high efficiency and long operational stability, calling for additional strategies to address this challenge. Here, we develop perovskite-molecule composite thin films for efficient and stable PeLEDs. The perovskite-molecule composite thin films consist of in-situ formed high-quality perovskite nanocrystals embedded in the electron-transport molecular matrix, which controls nucleation process of perovskites, leading to PeLEDs with a peak external quantum efficiency of 17.3% and half-lifetime of approximately 100 h. In addition, we find that the device degradation mechanism at high driving voltages is different from that at low driving voltages. This work provides an effective strategy and deep understanding for achieving efficient and stable PeLEDs from both material and device perspectives., The field of perovskite light-emitting diodes witnesses rapid development in both device processing strategies and performances. Here Wang et al. develop high-quality perovskite-molecule composite thin films and achieve high quantum efficiency of 17.3% and half-lifetime of 100 h.

Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. However, mixed halide perovskites usually suffer from phase segregation under electrical biases. Herein, we obtain high-performance and color-stable blue perovskite LEDs (PeLEDs) based on mixed bromide/ chloride three-dimensional (3D) structures. We demonstrate that the color instability of CsPb(Br1-xClx)(3) PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br1-xClx)(3) PeLEDs, with maximum external quantum efficiencies of up to 4.5% and high luminance of up to 5351 cd m(-2) in the sky-blue region (489 nm). Our work provides new insights into the color instability issue of mixed halide perovskites and can spur new development of high-performance and color-stable blue PeLEDs. Funding Agencies|ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1, 44651-1]; Swedish Foundation for International Cooperation in Research and Higher Education [CH2018-7736]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; China Scholarship CouncilChina Scholarship Council

Bright and efficient blue emission is key to further development of metal halide perovskite light-emitting diodes. Although modifying bromide/chloride composition is straightforward to achieve blue emission, practical implementation of this strategy has been challenging due to poor colour stability and severe photoluminescence quenching. Both detrimental effects become increasingly prominent in perovskites with the high chloride content that is desired to produce blue emission. Here, we solve these critical challenges in mixed halide perovskites and demonstrate spectrally stable blue perovskite light-emitting diodes (PeLEDs) over a wide range of emission wavelengths from 490 to 451 nanometres. The emission colour is directly tuned by modifying the halide composition. Particularly, our blue and deep-blue PeLEDs based on three-dimensional perovskites show high EQE values of 11.0% and 5.5% with emission peaks at 477 and 467 nm, respectively. These achievements are enabled by a vapour-assisted crystallization technique, which largely mitigates local compositional heterogeneity and ion migration.

The hole transport layer (HTL) plays a key role in determining the performance of planar perovskite solar cells (PSCs). Poly[bis(4-phenyl)(2,4, 6-triMethylphenyl)aMine] (PTAA), a polymer with good stability, is one of the promising HTL candidates for PSCs. However, notable interfacial carrier recombination limits the performance of PSCs based on PTAA HTL, due to the large gap between the highest-occupied molecular orbital (HOMO) of PTAA and the valance band maximum (VBM) of MAPbI3 perovskite as well as the low intrinsic hole mobility of PTAA. Herein, PTAA was doped by 3 wt% of molybdenum oxide (MoO3) to move down its HOMO by 0.16 eV, leading to a better matching with the MAPbI3 perovskite. Meanwhile, the MoO3 dopant was demonstrated to improve the hole transport in PTAA and hole extraction at the PTAA/perovskite interface. Eventually, the fabricated inverted planar PSCs using PTAA HTL with 3 wt% MoO3 achieved the PCE of 20.06% as compared to that of 17.71% by using pristine PTAA HTL. The present work thus proposes a simple approach to utilize MoO3 as a dopant to substantially improve the molecular HTLs for high-performance PSCs and other perovskite-based optoelectronics.

Halide perovskites with reduced-dimensionality (e.g., quasi-2D, Q-2D) have promising stability while retaining their high performance as compared to their three-dimensional counterpart. Generally, they are obtained in (A1)2(A2)n−1PbnI3n+1 thin films by adjusting A site cations, however, the underlying crystallization kinetics mechanism is less explored. In this manuscript, we employed ternary cations halides perovskite (BA)2(MA,FA)3Pb4I13 Q-2D perovskites as an archetypal model, to understand the principles that link the crystal orientation to the carrier behavior in the polycrystalline film. We reveal that appropriate FA+ incorporation can effectively control the perovskite crystallization kinetics, which reduces nonradiative recombination centers to acquire high-quality films with a limited nonorientated phase. We further developed an in situ photoluminescence technique to observe that the Q-2D phase (n = 2, 3, 4) was formed first followed by the generation of n = ∞ perovskite in Q-2D perovskites. These...

We design and synthesize an amino-functionalized conjugated polymer (PPDI-F3N) based on perylene diimide and use it as a multifunctional interfacial layer of TiO2/perovskite in conventional planar perovskite solar cells. The work function of TiO2 is modulated by PPDI-F3N to better align with the conduction band of the perovskite, leading to efficient charge extraction. PPDI-F3N can passivate the TiO2 surface to reduce the severe recombination loss and rapid degradation caused by oxygen vacancies on the UV-sensitive TiO2 surface. Moreover, modulated polarity of PPDI-F3N is beneficial to optimal perovskite crystallization and morphology. All these features contribute to a higher efficiency (18.3%) of the PSCs with the PPDI-F3N interlayer relative to the control devices without the interlayer (16.7%) as well as improved stability and a reduced hysteresis effect.

Pulsed laser deposition (PLD) is a powerful growth technique for thin films, where in situ doping and post-thermal annealing are the most effective ways to tune the crystalline and physical properties of the deposited films. This paper demonstrates that the crystallinity, transparency, and electrical properties of NiO films are well controlled by PLD, which determines the photovoltaic performance of CH3NH3PbI3−xClx-based perovskite solar cells with NiO films as the hole transport layers (HTLs). After post-annealing, the NiO films exhibit enhanced in-plane crystal orientation, high transmittance, and uniform surface morphology, and, accordingly, the power conversion efficiency (PCE) of the perovskite solar cell improves from 5.38% to 12.59%. Moreover, by doping the ablated target with lithium (Li), PLD can produce doped NiO:Li films with significantly enhanced electrical conductivity, which further improves the perovskite cell PCE from 12.59% to 15.51%. These results highlight the importance of optimizing the transporting layer properties toward high-performance inverted perovskite planar solar cells.

The electronic structures of rubrene films deposited on CH3NH3PbI3 perovskite have been investigated using in situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). It was found that rubrene molecules interacted weakly with the perovskite substrate. Due to charge redistribution at their interface, a downward ‘band bending’-like energy shift of ∼0.3 eV and an upward band bending of ∼0.1 eV were identified at the upper rubrene side and the CH3NH3PbI3 substrate side, respectively. After the energy level alignment was established at the rubrene/CH3NH3PbI3 interface, its highest occupied molecular orbital (HOMO)–valence band maximum (VBM) offset was found to be as low as ∼0.1 eV favoring the hole extraction with its lowest unoccupied molecular orbital (LUMO)–conduction band minimum (CBM) offset as large as ∼1.4 eV effectively blocking the undesired electron transfer from perovskite to rubrene. As a demonstration, simple inverted planar solar cell devices incorporating rubrene and rubrene/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layers (HTLs) were fabricated in this work and yielded a champion power conversion efficiency of 8.76% and 13.52%, respectively. Thus, the present work suggests that a rubrene thin film could serve as a promising hole transport layer for efficient perovskite-based solar cells.

Among the various methods to advance solar cell technologies, the implementation of nanoparticles with plasmonic effects is an effective way to make better use of incident light and manage carrier dynamics. Herein, for the first time we report the systematic synthesis of gold nanospheres or nanorods coated with a thin layer of titanium oxide (Au@TiO2) and use them to examine the plasmonic effect in planar heterojunction perovskite solar cells. The most efficient assembly mode is to embed the Au@TiO2 nanorods into the electron transport layer (ETL), which elevates the average power conversion efficiency (PCE) from 15.76% to 16.35%, mainly attributed to the short-circuit current enhancement. The optimized device assembled with Au@TiO2 nanorods delivers an efficiency of 20.10%. We further explored the plasmonic enhancement effect of Au@TiO2 nanorods based on the combination of UV-visible absorption spectroscopy, incident photon-to-current efficiency (IPCE), photoluminescence (PL) and transient photocurrent decay (TPC). The results indicate better charge separation/transfer as well as facilitated carrier transport in the presence of plasmonic particles. This work provides an insightful understanding of plasmonic effects in planar perovskite solar cells and also presents a promising approach for simultaneous photon and electron management.

A fused-ring electron acceptor based on indacenodithiophene (IDIC) was used to replace TiO2 and work as an electron transport layer in planar n–i–p perovskite solar cells. IDIC improves perovskite crystallinity and film quality due to its hydrophobicity and incompatible wetting surface. IDIC facilitates electron extraction and transport due to its high mobility and suitable energy levels matched with the perovskite. IDIC reduces charge recombination in the devices due to trap passivation at the perovskite surface. The IDIC-based devices exhibit a champion power conversion efficiency of 19.1%, which is higher than that of TiO2-based devices (17.4%). Moreover, the device stability is significantly improved by IDIC.

Pentacene thin film on CH3NH3PbI3 was studied by in-situ X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy to determine their interfacial energy level alignment. A 0.2 eV downward band bending together with a 0.1 eV interfacial dipole was found at the pentacene side, whereas there was no band bending found at the CH3NH3PbI3 side. The offset between CH3NH3PbI3 Valance Band Maximum (VBM) and pentacene Highest Occupied Molecular Orbital (HOMO) and that between CH3NH3PbI3 Conduction Band Minimum (CBM) and pentacene Lowest Unoccupied Molecular Orbital (LUMO) was determined to be 0.7 and 1.35 eV, respectively. The band alignment at this interface is favor of efficient hole transfer, which suggests pentacene as a viable HTL candidate to be explored in perovskite solar cells.

Hybrid organic–inorganic perovskite materials offer a range of interesting characteristics that are suitable for optoelectronic devices, such as photovoltaics. Along with the fast rise in device performance, a current density–voltage (J–V) hysteresis originating from defects and their movement has attracted intense attention, which renders challenges regarding the stability and reliability of the novel materials. Here, we carefully probe the effects of defects in perovskite materials and across interfaces within the device, in which bistable conductive states are achieved for the next generation of nonvolatile memory. The memory device shows an operating voltage as low as 0.25 V, and a decent ON/OFF ratio. More importantly, we correlate the defect density and hysteresis-index of different perovskite films with the corresponding memory device performance. The findings enrich our understanding of the working mechanism of perovskite memory devices, which will also benefit other organic–inorganic hybrid perovskite optoelectronics.

Crystal orientation has a great impact on the properties of perovskite films and the resultant device performance. Up to now, the exquisite control of crystal orientation (the preferred crystallographic planes and the crystal stacking mode with respect to the particular planes) in mixed-cation perovskites has received limited success, and the underlying mechanism that governs device performance is still not clear. Here, a thermodynamically favored crystal orientation in formamidinium/methylammonium (FA/MA) mixed-cation perovskites is finely tuned by composition engineering. Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently. The preferable growth along the (001) crystal plane, when lying parallel to the substrates, affects their charge transportation and collection properties. Under the optimized condition, the mixed-cation perovskite (FA1- x MAx PbI2.87 Br0.13 (Cl)) solar cells deliver a champion power conversion efficiency over 21%, with a certified efficiency of 20.50 ± 0.50%. The present work not only provides a vital step in understanding the intrinsic properties of mixed-cation perovskites but also lays the foundation for further investigation and application in perovskite optoelectronics.

Crystal orientations in multiple orders correlate to the properties of polycrystalline materials, and it is critical to manipulate these microstructural arrangements to enhance device performance. Herein, we report a controllable approach to manipulate the facet orientation within the ABX3 hybrid perovskites polycrystalline films by cation cascade doping at A-site. Two-dimensional synchrotron radiation grazing incidence wide-angle X-ray scattering is employed to probe the crystal orientations in multiple orders in mixed perovskites thin films, revealing a general pattern to guide crystal planes stacking upon extrinsic doping during crystallization. Different from previous studies, this method enables to adjust the crystal stacking mode of certain crystallographic planes in polycrystalline perovskites. Moreover, the preferred facet orientation is found to facilitate photocarrier transport across the absorber and pertaining interface in the resultant PV device, which provides an exemplary paradigm for further explorations that relate to the microstructures of hybrid perovskite materials and relevant optoelectronics., Crystal facet orientations of the polycrystalline hybrid lead halide perovskite thin films play a crucial role in determining the device performance. Here Zheng et al. demonstrate effective control of the crystal stacking mode by cation cascade doping, which promotes the charge transport in the photovoltaic device.

We systematically investigated the impact of stoichiometric ratio variation between PbX

The design of electron transport layers (ETLs) is crucial to the performance of optoelectronic devices. A composite ETL was constructed to overcome the poor carrier extraction issue in perovskite solar cells, resulting in a maximum PCE of 19.14% with reduced hysteresis. A similar enhancement phenomenon was observed in both devices based on TiO2 and SnO2 ETLs.

Among the various building blocks beyond polycrystalline thin films, perovskite wires have attracted extensive attention for potential applications including nanolasers, waveguides, field-effect transistors, and more. In this work, millimeter-scale lead iodine-based perovskite wires employing various A-site substitutions, namely, Cs, methylammonium (MA), and formamidinium (FA), have been synthesized via a new type solution method with nearly 100% yield. All of the three millimeter scale perovskite wires (MPWs) compositions exhibit relatively high quality, and CsPbI3 is proven to be monocrystalline along its entire length. Furthermore, the growth thermodynamics of the APbI3 MPWs with respect to A-site cation effect were studied thoroughly by various characterization techniques. Finally, single MPW photodetectors have been fabricated utilizing the APbI3 MPWs for studying the photoconductive properties, which show different sensitivities under illumination. This systematic synthesis method of solution-proces...

Correction for ‘A disorder-free conformation boosts phonon and charge transfer in an electron-deficient-core-based non-fullerene acceptor’ by Chujun Zhang et al., J. Mater. Chem. A, 2020, 8, 8566–8574, DOI: 10.1039/d0ta01260b.

The electronic structures of rubrene films deposited on CH

Engineering the chemical composition of organic and inorganic hybrid perovskite materials is one of the most feasible methods to boost the efficiency of perovskite solar cells with improved device stability. Among the diverse hybrid perovskite family of ABX

Recently, perovskite/Si devices have attracted enormous interest as an ideal technology for tandem cells, particularly due to the attributes from perovskite cell including low temperature processibility, tunable optical bandgap, and high open circuit voltage. Although solution process is considered to be cost effective and more widely adoptable for perovskite subcell, to the best of our knowledge, there has been no successful demonstration for the resulting high performance two-terminal perovskite/Si cells. In this manuscript, solution process is employed to fabricate the key components in the two-terminal perovskite/Si tandem solar cell, including tunneling junction and the perovskite absorber. The current density match between both cells is thoroughly studied by varing the perovskite bandgap from ≈1.55 to 1.69 eV. It was also revealed that the photovoltage modulation in the device is primarily associated to the band alignment over the perovskite and the tunneling materials. Therefore, a reverse scanned power conversion efficiency over 20% is demonstrated, the most efficient two-terminal perovskite/Si device based on solution processed perovskite subcells.

Engineering the chemical composition of organic and inorganic hybrid perovskite materials is one of the most feasible methods to boost the efficiency of perovskite solar cells with improved device stability. Among the diverse hybrid perovskite family of ABX3 , formamidinium (FA)-based mixed perovskite (e.g., FA1-x Csx PbI3 ) possesses optimum bandgaps, superior optoelectronic property, as well as thermal- and photostability, which is proven to be the most promising candidate for advanced solar cell. Here, FA0.9 Cs0.1 PbI3 (Cl) is implemented as the light-harvesting layer in planar devices, whereas a low temperature, two-step solution deposition method is employed for the first time in this materials system. This paper comprehensively exploits the role of Cs+ in the FA0.9 Cs0.1 PbI3 (Cl) perovskite that affects the precursor chemistry, film nucleation and grain growth, and defect property via pre-intercalation of CsI in the inorganic framework. In addition, the resultant FA0.9 Cs0.1 PbI3 (Cl) films are demonstrated to exhibit an improved optoelectronic property with an elevated device power conversion efficiency (PCE) of 18.6%, as well as a stable phase with substantial enhancement in humidity and thermal stability, as compared to that of FAPbI3 (Cl). The present method is able to be further extended to a more complicated (FA,MA,Cs)PbX3 material system by delivering a PCE of 19.8%.

A high‐mobility p‐type organic semiconductor based on benzodithiophene and diketopyrrolopyrrole with linear alkylthio substituents (BDTS‐2DPP) is used as a dual function interfacial layer to modify the interface of perovskite/2,2′,7,7′‐tetrakis(N,N′‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene in planar perovskite solar cells. The BDTS‐2DPP layer can remarkably passivate the surface defects of perovskite through the formation of Lewis adduct between the under‐coordinated Pb atoms in perovskite and S atoms in BDTS‐2DPP, and also shows efficient hole extraction and transfer properties. The devices with BDTS‐2DPP interlayer show a peak power conversion efficiency of 18.2%, which is higher than that of reference devices without the BDTS‐2DPP interlayer (16.9%). Moreover, the hydrophobic BDTS‐2DPP interlayer effectively protects the perovskite against moisture, leading to enhanced device stability.

Minimization of defects in absorber materials is essential for hybrid perovskite solar cells, especially when constructing thick polycrystalline layers in a planar configuration. Here, a simple methylamine solution-based additive is reported to improve film quality with nearly an order of magnitude reduction in intrinsic defect concentration. In the resultant film, an increase in carrier lifetime as a result of a decrease in shallow electronic disorder is observed. This superior crystalline film quality is further evidenced via a doubled spin relaxation time as compared with other reports. Bearing sufficient carrier diffusion length, a thick absorber layer (≈650 nm) is implemented in planar devices to achieve a champion power conversion efficiency of 20.02% with a stabilized output efficiency of 19.01% under one sun illumination. This work demonstrates a simple approach to improve hybrid perovskite film quality by substantial reduction of intrinsic defects for wide applications in optoelectronics.

Here, we introduced acetamidine (C2H3N2H3, Aa)-based salt as an additive in the fabrication of perovskite (CH3NH3PbI3) layer for perovskite solar cells. It was found that as an amidine-based salt, this additive successfully enhanced the crystallinity of CH3NH3PbI3 and helped to form smooth and uniform films with comparable grain size and full coverage. Besides, perovskite film with additive showed a much longer carrier lifetime and an obviously enhanced open-circuit voltage in the corresponding devices, indicating that the acetamidine-based salt can reduce the carrier recombination in both the film and device. We further demonstrate a promising perovskite device based on acetamidine salt by using a configuration of ITO/TiO2/Perovskite/Spiro-OMeTAD/Au under < 150℃ fabrication condition. A power conversion efficiency (PCE) of 16.54% was achieved, which is much higher than the control device without acetamidine salt. These results present a simple method for film quality optimization of perovskite to further improve photovoltaic performances of perovskite solar cells, which may also benefit the exploration of A cation in perovskite materials.

Organic–inorganic halide perovskite has received extensive attention as a light harvester for next-generation low-cost and high-performance photovoltaics. Its superior optoelectronic properties are attractive among most thin film absorber materials, such as an extremely high absorption coefficient, optimal band gap, ambipolar carrier transport property, and high defects tolerance. However, it requires suitable electrodes and carrier transport materials to fulfill efficient photovoltaic process within an entire device. Thus, the interfaces along the device play a crucial role in determining device photovoltaic performance. Here, the progress of understanding interfaces in perovskite photovoltaics is reviewed from the perspective of processing chemistry and photophysics of carriers, which are the key parameters for the corresponding device photovoltaic behavior. This study is mainly focused on the relevant working mechanism, interface design fundamentals, and the resulting carrier dynamic control over the entire architecture. The study of the interfaces with appropriate materials design provides a fundamental understanding of the photocarrier behavior, including separation, transportation, and collection. The accumulative efforts will contribute to the construction of high-efficiency perovskite-based single junction and multijunction photovoltaic devices. It also affects other properties of perovskite solar cells, including J–V hysteresis phenomenon, and long-term stability. Suggestions with respect to required improvements and future research directions are provided based on the current field of available literature.