The purity of tin (Sn) sources is vital in terms of Sn‐based perovskite solar cells’ fabrication. In article no. 1800136, Zhiwei Liu, Zuqiang Bian, and co‐workers propose a simple purification method to reduce the detrimental Sn4+ existing in the precursor solutions by adding Sn powder. Aft er purification, the efficiency of FASnI3‐based solar cells prepared from 99% SnI2 is elevated from 0.09% to a maximum value of 6.75% due to the improved morphology and lessened recombination loss.
Unbiased biocatalytic solar-to-chemical conversion by FeOOH/BiVO4/perovskite tandem structure
Unbiased biocatalytic solar-to-chemical conversion by FeOOH/BiVO<sub>4</sub>/perovskite tandem structure, Published online: 11 October 2018; doi:10.1038/s41467-018-06687-z
Photoelectrochemical (PEC) cell platforms typically need an electrical bias that drives the electron transfer from the photoanode to the photocathode. Here, the authors report a bias-free PEC tandem device for solar-driven redox biocatalysis.
An effective strategy of promoting grain growth and defects passivation simultaneously for perovskite film by using Ni2+ addition is demonstrated. An appreciated efficiency of 20.6% can be achieved for an inverted planar perovskite solar cells device based on a CH3NH3PbI3 (Ni2+) film.
Today's state‐of‐the‐art perovskite solar cells (PSCs) are utilizing polycrystalline perovskite thin films via solution‐processing at low temperature (<150 °C). It is extremely significant to enlarge grain size and passivate trap states for perovskite thin films to achieve high power conversion efficiency. Herein, a strategy for defect passivation of perovskite films via metal ion Ni2+ is for the first time reported. It is found that addition of Ni2+ can significantly generate polyporous PbI2 films due to a different solubility between NiCl2 and PbI2 which benefits penetration of MAI and thus formation of large grain perovskite films eventually. It further demonstrated that Ni2+ ions can effectively passivate PbI3 − antisite defects and restrain the generation of Pb0 by interacting with the under‐coordinated halide anions and halide‐rich antisites. Therefore, introducing moderate Ni2+ ions result in a significant increase in photoluminescence lifetime from 285 to 732 ns. Accordingly, a power conversion efficiency of 20.61% can be achieved for the 3% Ni2+ addition‐based PSCs with an enhanced cell stability under ambient conditions. This work provides a promising route toward perovskite films featuring with high crystallinity and low trap‐density.
Highly efficient perovskite quantum‐dot light‐emitting diodes (QLEDs) through organic–inorganic hybrid ligand (OIHL) passivation strategy are reported. The OIHL‐passivated films exhibit enhanced radiative recombination and effective electrical transportation features, which make QLEDs have a maximum peak external quantum efficiency (EQE) of 16.48%, which is the most efficient in the field of perovskite‐based LEDs up to now.
Perovskite quantum dots (QDs) with high photoluminescence quantum yields (PLQYs) and narrow emission peak hold promise for next‐generation flexible and high‐definition displays. However, perovskite QD films often suffer from low PLQYs due to the dynamic characteristics between the QD's surface and organic ligands and inefficient electrical transportation resulting from long hydrocarbon organic ligands as highly insulating barrier, which impair the ensuing device performance. Here, a general organic–inorganic hybrid ligand (OIHL) strategy is reported on to passivate perovskite QDs for highly efficient electroluminescent devices. Films based on QDs through OIHLs exhibit enhanced radiative recombination and effective electrical transportation properties compared to the primal QDs. After the OIHL passivation, QD‐based light‐emitting diodes (QLEDs) exhibit a maximum peak external quantum efficiency (EQE) of 16.48%, which is the most efficient electroluminescent device in the field of perovskite‐based LEDs up to date. The proposed OIHL passivation strategy positions perovskite QDs as an extremely promising prospect in future applications of high‐definition displays, high‐quality lightings, as well as solar cells.
A balanced crystallinity of donor and acceptor is finely controlled by combining blade‐coating and ternary strategies in a PBDB‐T:PTB7‐Th:FOIC‐based organic solar cell, resulting in well‐matched hole and electron mobilities with a power conversion efficiency of 12.02%.
As a prototype tool for slot‐die coating, blade‐coating exhibits excellent compatibility with large‐area roll‐to‐roll coating. A ternary organic solar cell based on PBDB‐T:PTB7‐Th:FOIC blends is fabricated by blade‐coating and exhibits a power conversion efficiency of 12.02%, which is one of the highest values for the printed organic solar cells in ambient environment. It is demonstrated that blade‐coating can enhance crystallization of these three materials, but the degree of induction is different (FOIC > PBDB‐T > PTB7‐Th). Thus, the blade‐coated PBDB‐T:FOIC device presents much higher electron mobility than hole mobility due to the very high crystallinity of FOIC. Upon the addition of PTB7‐Th into the blade‐coated PBDB‐T:FOIC blends, the crystallinity of FOIC decreases together with the corresponding electron mobility, due to the better miscibility between PTB7‐Th and FOIC. The ternary strategy not only maintains the well‐matched crystallinity and mobilities, but also increases the photocurrent with complementary light absorption as well as the Förster resonant energy transfer. Furthermore, small domains with homogeneously distributed nanofibers are observed in favor of the exciton dissociation and charge transport. This combination of blade‐coating and ternary strategies exhibits excellent synergistic effect in optimizing morphology, showing great potential in the large‐area fabrication of highly efficient organic solar cells.
By applying anisole, a one‐step antisolvent assistant spin‐coating method with an ultrawide process window to fabricate perovskite thin films is developed. The application of these films in n–i–p structured perovskite solar cells leads to a maximum PCE of 19.76% for a small area (0.14 cm2), 17.39% for a large area (1.08 cm2), and a large‐sized perovskite thin film of 196 cm2.
Photovoltaic technologies based on perovskite absorber materials have led this optoelectronic field into a brand‐new horizon. However, the present antisolvents used in the one‐step spin‐coating method always encounter problems with the very narrow process window. Herein, anisole is introduced into the one‐step spin‐coating method, and the technology is developed to fabricate perovskite thin films with ultrawide processing window with a dimethylformamide (DMF):dimethyl sulfoxide (DMSO) ratio varying from 6:4 to 9:1 in the precursor solution, anisole dripping time ranging from 5 to 25 s, and an antisolvent volume varying from 0.1 to 0.9 mL. Perovskite thin films as large as 100 cm2 are successfully fabricated using this method. Maximum photoelectric conversion efficiencies of 19.76% for small‐area (0.14 cm2) and 17.39% for large‐area (1.08 cm2) perovskite solar cell devices are obtained. It is also found that there are intermolecular hydrogen‐bonding forces between anisole and DMF/DMSO that play critical roles in the wide process window. These results provide a deeper understanding of the crystallizing procedure of perovskite during the one‐step spin‐coating process.
In article no. 1800132, Jin‐Peng Yang, Nobuo Ueno, Satoshi Kera, and co‐workers perform observations of the top valence band structure of CH3NH3PbI3 single crystals using angle‐resolved ultraviolet photoelectron spectroscopy of the cleaved single‐crystal surfaces. The combination of freshly cleaved crystal surfaces and determination of the exact orientation of the crystal axes using diffraction techniques successfully measures well‐determined crystal directions.
High‐performance air‐stable perovskite solar cells are obtained after embedding carbon nanodots and urea into the perovskite. The best device performance features a power conversion efficiency of 20.2%, with negligible hysteresis. The devices displays excellent air‐stability for over 500 h without any encapsulation under 40% humidity (25 °C).
Carbonized bamboo‐derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid‐ and hydroxyl‐rich CNDs interact with the perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high‐performance p–i–n PSCs having the structure indium tin oxide/NiO x /CH3NH3PbI3 (MAPbI3)/PC61BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% ± 0.39% to 16.47% ± 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%—the result of a significant increase in the crystal size and a lower content of grain boundary defects and, therefore, longer carrier lifetimes. Cells containing these two additives (without encapsulation) exhibit excellent shelf‐life and air‐stability, maintaining their high PCEs after storage in air—at a temperature of 25 °C and a humidity of 40%—for over 500 h. This performance is among of the best ever reported for p–i–n PSC devices incorporating carbon‐based additives.
Nanotwinned grain structures in the TiO2 nanotube walls can be induced for “single‐walled” nanotubes via high‐temperature treatment in pure oxygen atmosphere. Such twinned nanotubes show a strongly enhanced conductivity and photogenerated charge transport compared to classical nanotubes and can lead to efficiencies of up to 10.23% in dye‐sensitized solar cells.
Titania is one of the key materials used in 1D, 2D, and 3D nanostructures as electron transport media in energy conversion devices. In the present study, it is shown that the electronic properties of TiO2 nanotubes can be drastically improved by inducing a nanotwinned grain structure in the nanotube wall. This structure can be exclusively induced for “single‐walled” nanotubes with a high‐temperature treatment in pure oxygen atmospheres. Nanotubes with a twinned grain structure within the tube wall show a strongly enhanced conductivity and photogenerated charge transport compared to classic nanotubes. This remarkable improvement is exemplified in the electronic properties by using nanotwinned TiO2 nanotubes in dye‐sensitized solar cells where a significant increase in efficiency of up to 10.2% is achieved.
Herein, the authors use PEACl treatment to significantly improve the moisture‐resistance of the CsPbI2Br film. It is found that hydrophobic PEA+ forms on the CsPbI2Br surface, meanwhile, chlorine doped into the CsPbI2Br lattice leading to smaller lattice structure and improved crystallization quality. As a result, the present device achieves a high power conversion efficiency of 14.05% and much improved moisture resistance.
CsPbI2Br has been recognized as a promising material for photovoltaic applications due to its excellent optoelectronic properties and compositional stability. Unfortunately, its desired perovskite phase is not stable in humid environments as it is spontaneously transformed into a yellow non‐perovskite phase. Herein, we present our strategy to use phenylethylammonium chlorine (PEACl) treatment to significantly improve the moisture‐resistance of the CsPbI2Br film without compromising its high solar cell efficiency. It is found that: 1) small‐sized hydrophobic aromatic group PEA+ forms in the edge‐on orientation on the CsPbI2Br surface and 2) smaller halide Cl− is doped into the CsPbI2Br lattice during post‐annealing, leading to a smaller lattice structure with beneficial crystallization quality. Compared with the reference sample without the PEACl treatment, the present device achieves a comparable power‐conversion efficiency of 14.05% and much improved moisture resistance.
SrCl2 is introduced as a co‐precursor in the synthesis of CsPbI3 perovskite nanocrystals to realize their simultaneous Sr2+ cation doping and surface Cl− anion passivation. The stability of the nanocrystals is improved, and light‐emitting devices with a high external quantum efficiency of 13.5% are realized.
A method is proposed to improve the photo/electroluminescence efficiency and stability of CsPbI3 perovskite nanocrystals (NCs) by using SrCl2 as a co‐precursor. The SrCl2 is chosen as the dopant to synthesize the CsPbI3 NCs. Because the ion radius of Sr2+ (1.18 Å) is slightly smaller than that of Pb2+ (1.19 Å) ions, divalent Sr2+ cations can partly replace the Pb2+ ions in the lattice structure of perovskite NCs and cause a slight lattice contraction. At the same time, Cl− anions from SrCl2 are able to efficiently passivate surface defect states of CsPbI3 nanocrystals, thus converting nonradiative trap states to radiative states. The simultaneous Sr2+ ion doping and surface Cl− ion passivation result in the enhanced photoluminescence quantum yield (up to 84%), elongated emission lifetime, and improved stability. Sr2+‐doped CsPbI3 NCs are employed to produce light‐emitting devices with a high external quantum yield of 13.5%.
A diboron‐assisted strategy for tuning interfacial defects in formamidinium‐iodide‐based perovskite solar cells is demonstrated to decompose the unreacted organic‐halide species at the surface by coating B2Cat2 on top of the perovskite films, which can suppress the nonradiative recombination loss and boost power conversion efficiency. This approach paves a new way for mitigating defects and improving device performance.
Metal halide perovskite films are endowed with the nature of ions and polycrystallinity. Formamidinium iodide (FAI)‐based perovskite films, which include large cations (FA) incorporated into the crystal lattice, are most likely to induce local defects due to the presence of the unreacted FAI species. Here, a diboron‐assisted strategy is demonstrated to control the defects induced by the unreacted FAI both inside the grain boundaries and at the surface regions. The diboron compound (C12H10B2O4) can selectively react with unreacted FAI, leading to reduced defect densities. Nonradiative recombination between a perovskite film and a hole‐extraction layer is mitigated considerably after the introduction of the proposed approach and charge‐carrier extraction is improved as well. A champion power conversion efficiency of 21.11% is therefore obtained with a stabilized power output of 20.83% at the maximum power point for planar perovskite solar cells. The optimized device also delivers negligible hysteresis effect under various scanning conditions. This approach paves a new way for mitigating defects and improving device performance.
This study investigates the impact of chloride, bromide, or diiodooctane on the perovskite ink wetting properties, as well as the storage of the substrates. All of the inner layer is inkjet‐printed and annealed at low temperature. This leads to the successful demonstration of 10.7% efficient chlorine‐doped methylammonium lead iodide solar cells.
Considering the recent advances in the fundamental understanding of perovskite devices as well as in the demonstration of larger stability under working conditions, specific attention has still to be paid for their processing for low‐cost applications. Here, the successful demonstration of 10.7% efficient chlorine‐doped methylammonium lead iodide (CH3NH3PbI3‐xClx) solar cells based on a fully inkjet‐printed processed under ambient conditions and at low temperature (<90 °C) is reported. A huge hysteresis is observed and the efficiency drops down to 6.4% for the forward scan. The Owens–Wendt–Rabel and Kaelble model is applied to investigate the impact of chloride, bromide, or diiodooctane on the perovskite ink wetting properties. A low surface energy of the substrate provokes dewetting during the perovskite printing. The use of chlorine or bromide tends to increase the wettability of the perovskite ink, improving the impregnation of the ink in porous materials. This work shows the critical importance of properly storing these substrates prior to active layer deposition, in order to produce homogenous layers by inkjet‐printing. The successful printing of all inner layers, excluding bottom and top electrodes, in ambient atmosphere is an additional step toward their expected development at a larger scale by the printed electronic industry.
Single material organic solar cells (SMOSCs) based on ambivalent donor acceptor materials are the ultimate stage of simplification of organic solar cells and a possible solution to the instability of multicomponent cells. Impressive progress in both polymeric and molecular SMOSCs has been recently reported and the related perspectives and fundamental issues are critically discussed here.
Single material organic solar cells (SMOSCs) are based on ambivalent materials containing electron donor (D) and acceptor (A) units capable to ensure the basic functions of light absorption, exciton dissociation, and charge transport. Compared to bicomponent bulk heterojunctions, SMOSCs present several major advantages such as considerable simplification of cell fabrication and a strong stabilization of the morphology of the D/A interface, and thus of the cell lifetime. In addition to these technical issues, SMOSCs pose fundamental questions regarding the possible formation, and dissociation of excitons on the same molecular D–A architecture. SMOSCs are developed with various approaches, namely “double‐cable” polymers, block copolymers, oligomers, and molecules that differ by the donor platform: polymer or molecule, the nature of A, the D–A connection, and the intra‐ and intermolecular interactions of D and A. Although for several years the maximum efficiency of SMOSCs has remained limited to 1.0–1.5%, impressive progress has been recently accomplished leading to SMOSCs with 4.0–5.0% efficiency. Here, recent advances in the synthesis of D–A materials for SMOSCs are presented in the broader context of the chemistry of organic photovoltaic materials in order to discuss possible directions for future research.
The 2D Ti3C2T x additive can enlarge the grain size of the perovskite film due to the weak interactions between the termination groups (F and OH) and CH3NH3I. Due to these interactions, the perovskite nuclei generate around the additive and the number of nuclei is suppressed. Fewer nuclei make the grain size larger than that of the pristine film.
MXenes, a newly intriguing family of 2D materials, have recently attracted considerable attention owing to their excellent properties such as high electrical conductivity and mobility, tunable structure, and termination groups. Here, the Ti3C2T x MXene is incorporated into the perovskite absorber layer for the first time, which aims for efficiency enhancement. Results show that the termination groups of Ti3C2T x can retard the crystallization rate, thereby increasing the crystal size of CH3NH3PbI3. It is found that the high electrical conductivity and mobility of MXene can accelerate the charge transfer. After optimizing the key parameters, 12% enhancement in device performance is achieved by 0.03 wt% amount of MXene additive. This work unlocks opportunities for the use of MXene as potential materials in perovskite solar cell applications.
Optimized ternary organic solar cells (OSCs) exhibit a power conversion efficiency of 12.55% with simultaneously improved J SC and fill factor due to the complementary absorption spectra and good compatibility of MeIC and MeIC2. The two acceptors with good compatibility and similar lowest unoccupied molecular orbital levels may prefer to form one alloyed state for efficient electron transport in ternary OSCs.
Efficient ternary organic solar cells (OSCs) are fabricated by employing a polymer PBT1‐C as the donor and two non‐fullerene materials, MeIC and MeIC2, as one alloyed acceptor. The optimized ternary OSCs with 30 wt% MeIC2 in acceptors achieve a power conversion efficiency (PCE) of 12.55%, which is much higher than that of 11.47% for MeIC‐based binary OSCs and 11.41% for MeIC2‐based binary OSCs. The >9.4% improvement in PCE is mainly attributed to the optimized photon harvesting and morphology of ternary active layers, resulting in the simultaneously improved short‐circuit current and fill factor. Furthermore, good compatibility and similar lowest unoccupied molecular orbital energy levels of MeIC and MeIC2 are beneficial to form one alloyed acceptor for efficient electron transport in the ternary active layers. This work may provide new insight when selecting the third component for preparing efficient ternary OSCs.
Stable α‐CsPbI3 is synthesized by incorporating cation 2‐(naphthalene‐1‐yl)ethanamine (NEA) for perovskite‐based light‐emitting diodes (PeLED). A high external quantum (EQE) of 8.65% is successfully demonstrated for the characteristic red emission ≈682 nm representing the highest value among Cs‐based red PeLEDs up to now. More importantly, corresponding PeLEDs exhibit outstanding stability with EQE retaining 90% after 3 months storage.
Recently, inorganic cesium–lead halide perovskites with high thermal stability have attracted much attention as promising light‐emitting material for research of perovskite‐based light‐emitting diodes (PeLEDs) toward high‐definition displays. However, the CsPbI3‐based red PeLEDs still suffer low external quantum efficiency (EQE) and poor device stability due to the spontaneous phase transition from cubic CsPbI3 (α‐CsPbI3) to nonradiative orthorhombic phase (δ‐CsPbI3) under ambient conditions. Here, a feasible approach is reported on phase engineering by incorporating the long‐chain cation (e.g., 2‐(naphthalene‐1‐yl)ethanamine (NEA)) in CsPbI3 for stable and high‐performance CsPbI3‐based red light‐emitting diodes (LEDs). A high EQE of 8.65% is successfully achieved for the characteristic red emission at ≈682 nm representing the highest value among Cs‐based red PeLEDs up to now. More importantly, the corresponding PeLEDs exhibit outstanding stability with EQE retaining 90% after 3 months of storage. These results verify the potential of using cesium‐based inorganic perovskite as viable alternatives to methylammonium (MA)‐ or formamidinium (FA)‐based perovskite for desirable practical applications.
Perovskite solar cells produced by roll‐to‐roll (R2R) slot die coating on flexible substrates at ambient atmosphere from nontoxic solvents demonstrate an average stabilized efficiency of 12%, with the best value of 13.5%. This study is the first public demonstration of R2R slot die coating of perovskites on 30 cm wide substrates with the deposition and drying speed of 3–5 m min−1.
The feasibility of upscaling the perovskite solar cells technologies to high volume production using roll‐to‐roll (R2R) slot die coating is demonstrated in this study. Perovskite solar cells are produced by R2R slot die coating on flexible substrates with a width of 30 cm and the web speed of 3–5 m min−1. R2R deposition of the electron transport layer and perovskite is performed at ambient atmosphere from nontoxic solvents compatible with industrial manufacturing. The average stabilized power conversion efficiency of the devices made on different areas of the foil is 12%, with the best value of 13.5%. The demonstrated achievement is an important milestone and a big solid step toward future commercialization of perovskite‐based solar cells technologies.
