2D Perovskites
In article number 2100495, Hua Yu, Xueqing Xu, and co-workers introduced the mixed organic spacer cation n-butylammonium (BA) and 1-naphthalenemethylammonium (1-NMA) in 2D perovskites to manipulate the interlayer interactions between bulky spacer cations and inorganic slabs, leading to an efficient and air-stable 2D perovskite solar cell.
Nature Communications, Published online: 06 October 2021; doi:10.1038/s41467-021-26121-1
Perovskite photovoltaics has become more competitive against silicon counterpart in reducing cost of solar energy, yet the management of toxic lead hampers it application. Here, the authors propose a cost-effective environmental-friendly approach to recycle lead and transparent conductors.
Pressure is a fascinating tool to tune structural and optical material properties and can be used to design novel, lead-free materials for perovskite solar cells.
Metal halide perovskites have drawn significant attention for their promising physical properties and their possible application in solar cells and light-emitting diodes. Research and technology have made extraordinary progress in this field, but some issues are still to be tackled. In fact, most of the used materials contain lead, which is highly toxic. For this reason, many efforts have been made on substituting lead with other elements to design more environmentally friendly solar cells. However, devices based on lead-free materials still show relatively low efficiencies. Physical properties tuning of such materials, to improve their performance, can be achieved in different ways, and among them pressure can be thought of as a green method for this aim as well as a powerful technique to systematically explore structure–property relationships. The possibility of unveiling and discovering novel and appealing optical and electronic features, resulting from the application of an external pressure, can open an effective route to design more performing materials.
Nature Materials, Published online: 04 October 2021; doi:10.1038/s41563-021-01101-4
The topological nature of the electronic structure of two-dimensional ferromagnetic SrRuO3 and its relationship to the anomalous Hall effect is explored through transport measurements, angle-resolved photoemission spectroscopy and theoretical modelling.
This study introduces an octyl-diammonium lead iodide (ODAPbI4) interlayer onto the hole-transporting layer, which significantly reduces nonradiative recombination of wide-bandgap perovskite devices, enhancing the efficiency of wide-bandgap devices beyond 21%. By coupling a semitransparent device with a Cu2ZnSn(S,Se)4 (CZTSSe) cell, a four terminal perovskite/CZTSSe tandem cell with a power conversion efficiency of 22.27% is achieved.
Wide-bandgap perovskites have attracted substantial attention due to their important role in serving as a top absorber in tandem solar cells (TSCs). However, wide-bandgap perovskite solar cells (PVSCs) typically suffer from severe non-radiative recombination loss and therefore exhibit high open-circuit voltage (V OC) deficits. To address these issues, a 2D octyl-diammonium lead iodide interlayer is adopted onto the hole-transporting layer to induce the formation of an ultrathin quasi-2D perovskite that is close to the hole-selective interface. This approach not only accelerates hole transfer and retards hole accumulation but also reduces the trap density in the perovskite layer on top, thereby efficiently suppresses non-radiative recombination pathways. Consequently, the champion wide-bandgap device (≈1.66 eV) exhibits a power conversion efficiency (PCE) of 21.05% with a V OC of 1.23 V, where the V OC deficit of 0.43 V is among the lowest values for inverted wide-bandgap PVSCs. Moreover, by stacking a semi-transparent perovskite top cell on a 1.1 eV Cu2ZnSn(S,Se)4 (CZTSSe) bottom cell, a 22.27% PCE was achieved on a perovskite/CZTSSe four-terminal tandem solar cell, paving the way for all-solution-processed, low-cost, and efficient TSCs with mitigated energy loss in the wide-bandgap top cells.
A facile strategy to achieve both proper solubility and pre-aggregation in non-halogenated solvents by selecting suitable donor/acceptor materials and subtle tuning of solvent compositions was developed. The derived solar cells achieve a high efficiency up to 18%, representing the highest value reported for non-halogenated solvent processed devices.
Using non-halogenated solvents to process organic solar cells is preferable because they are less harmful to human health. However, it is challenging to mitigate the delicate trade-offs between solubility and pre-aggregation of organic semiconductors to maintain similar high device efficiencies as those processed by chlorinated solvents. The need for rigorous control of the kinetics between processing temperature and delay time inevitably complicates device processing for achieving reproducible performance. Herein, the authors develop a facile method to achieve proper solubility and pre-aggregation in non-halogenated solvents by selecting suitable donor/acceptor materials and subtle tuning of solvent compositions. This results in films with a high degree of ordering and suitably sized phase separation. Solar cells derived from this process can achieve a high power conversion efficiency up to 18%, which is the highest value reported for non-halogenated solvent processed devices. This impressive result is achieved through synergistically reduced non-radiative loss and enhanced charge generation.
A flexible hybrid solar cell with extended photoresponse, high power conversion efficiency of 21.73%, and excellent mechanical durability is realized by incorporating a low-bandgap organic bulk heterojunction layer into perovskite solar cells. Taking advantage of these impressive device performance, the flexible solar cell–sensor integrated system is demonstrated for real-time temperature monitoring via on-body evaluation.
Lead halide perovskite and organic solar cells (PSCs and OSCs) are considered as the prime candidates currently for clean energy applications due to their solution and low-temperature processibility. Nevertheless, the substantial photon loss in near-infrared (NIR) region and relatively large photovoltage deficit need to be improved to enable their uses in high-performance solar cells. To mitigate these disadvantages, low-bandgap organic bulk-heterojunction (BHJ) layer into inverted PSCs to construct facile hybrid solar cells (HSCs) is integrated. By optimizing the BHJ components, an excellent power conversion efficiency (PCE) of 23.80%, with a decent open-circuit voltage (V oc) of 1.146 V and extended photoresponse over 950 nm for rigid HSCs is achieved. The resultant devices also exhibit superior long-term (over 1000 h) ambient- and photostability compared to those from single-component PSCs and OSCs. More importantly, a champion PCE of 21.73% and excellent mechanical durability can also be achieved in flexible HSCs, which is the highest efficiency reported for flexible solar cells to date. Taking advantage of these impressive device performances, flexible HSCs into a power source for wearable sensors to demonstrate real-time temperature monitoring are successfully integrated.
A facile one-step deposition method is developed for preparing a Sb2S3 nanoparticle film with a preferential [221]-orientation to a certain extent on a TiO2 nanoparticle film, where the thickness and trap density of the Sb2S3 film are easily controlled. The efficiency of 5.74% is achieved under AM 1.5G illumination in such Sb2S3/TiO2 planar heterojunction solar cells.
Antimony sulfide (Sb2S3) is a promising photon-harvesting material for solar cells. Herein, a facile one-step deposition method is reported for controllably preparing Sb2S3 nanoparticle films with a preferential [221]-orientation to a certain extent from a novel precursor solution, formed by dissolving antimony acetate and thiourea in acidified N,N-dimethylformamide. With titania (TiO2) nanoparticle films as substrates for in situ-growing Sb2S3 films, the high-quality Sb2S3/TiO2 planar heterojunction films are obtained for efficient solar cells. The effects of the concentration and [S]/[Sb] molar ratio in the precursor solution on the Sb2S3 film formation and the device performance are investigated. A considerable power conversion efficiency of 5.74% is achieved under AM 1.5G illumination (100 mW cm−2), which is the highest efficiency for the solar cells based on solution-processed Sb2S3 nanoparticle films by one-step deposition method without further modification. A promising solution-processing method is provided to prepare high-quality Sb2S3 films for efficient solar cells and other optoelectronics.
Very thin crystalline Si (c-Si) solar cells may open various opportunities for flexible and light-weight photovoltaic modules as well as reducing the carbon footprint of solar cell manufacture. A bendable, 56-mm-thick c-Si heterojunction cell is developed to explore the potential of very thin c-Si cells. It demonstrates a high open-circuit voltage of 754 mV and an efficiency of 23.27%.
The silicon heterojunction (SHJ) is a crystalline silicon (c-Si) solar cell device architecture capable of achieving high efficiencies due to excellent surface passivation realized by hydrogenated amorphous silicon (a-Si:H) thin layers. The SHJ architecture also allows to process thinner Si wafers due to the structural symmetry and the low processing temperature. Herein, an attempt to increase the performance of very thin c-Si solar cells is made, using an advanced SHJ architecture. By replacing the conventional a-Si:H by hydrogenated nanocrystalline silicon (nc-Si:H) in the hole contact layer, an increase in all solar cell parameters over a wide range of wafer thicknesses from 50 to 400 μm is observed. This also provides an open-circuit voltage (V OC) of 754 mV with the very thin absorber, which is the highest V OC independently confirmed under standard test conditions (STCs) among any c-Si solar cells ever reported. As a result, a notable efficiency of 23.27% is realized in a SHJ cell with an average thickness of only 56.2 μm. These results demonstrate the high potential of very thin c-Si solar cells that may open various opportunities for flexible and lightweight c-Si modules, as well as reducing the carbon footprint of solar cell manufacture.
An electron transport layer-free (ETL-free) perovskite solar cell is demonstrated by the addition of EMIMPF6 ionic liquid within the perovskite layer. The integrated EMIMPF6 assisted the internal charge collection and favored the interfacial charge transfer from perovskite to FTO glass substrate, contributing to the high performance of the ETL-free device.
Perovskite solar cells (PSCs) have achieved unprecedented power conversion efficiency improvements, and further development is stepping to industrialization. In terms of industrial manufacturing, simplifying the solar cell structure is critical in both fabrication process design and cost control. Due to the bipolar charge transport nature of perovskites, the elimination of the charge carrier transport layer is possible. Herein, EMIMPF6 ionic liquid is incorporated into the perovskite film to modulate the energy-level alignment and the charge transfer kinetics, demonstrating a high-performance electron transport layer-free (ETL-free) PSC. The integrated EMIMPF6 assisted the internal charge collection and favored the interfacial charge transfer from perovskite to FTO substrate, contributing to the high performance of ETL-free PSCs. The ETL-free PSCs showed a conversion efficiency of 16.2%, which is comparable with its conventional counterpart. This work provides a solution to simplify the PSC structure and would have an impact on designing a scalable manufacturing process for PSCs.
Power conversion efficiency of the Cs x FA1−x Pb(I0.94Br0.06)3-based perovskite solar cells (PSCs) as a function of time and a cross-sectional transmission electron microscopy (TEM) image to demonstrate stable interface of K5B active layer-based PSC after 1128 h.
Formamidinium lead iodide (FAPbI3) is ideal for highly efficient and operationally stable perovskite solar cells (PSC). However, a primary challenge for FAPbI3 PSC is to suppress the phase transition from the photoactive black phase into the yellow nonperovskite δ-phase. The preparation of Cs-containing mixed FAPbI3 perovskite by cation stoichiometric engineering is demonstrated and the influence of the Cs/FA ratio on its phase stability and device performance is discussed. By exploring the optimal ratio of Cs and FA cations in Cs x FA1−x Pb(I0.94Br0.06)3 perovskite, an inverted planar device with Cs0.17FA0.83Pb(I0.94Br0.06)3 composition shows the best power conversion efficiency (PCE) of 16.5% in an active area of 1.08 cm2. More importantly, the Cs0.17FA0.83Pb(I0.94Br0.06)3 perovskite photoactive layer showed remarkable long-term stability, maintaining 88.1% of its initial efficiency for 1128 h in the presence of moisture and oxygen and without any encapsulation. The excellent long-term stability is found to originate from the appropriate tolerance factor and low thermodynamic decomposition energy, which underpins the strong potential for the commercialization of Cs-containing mixed FAPbI3 PSCs.
High-quality (FA0.83MA0.17)0.95Cs0.05Pb(I0.83Br0.17)3 perovskite films are fabricated by solvent volatilization. This method does not need an antisolvent technique and presents significant potential for large-scale and large-area device fabrication. A high power conversion efficiency of 20.6% is obtained by the films. A large area perovskite film of 10 × 10 cm2 can be fabricated by the method.
Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA0.83MA0.17)0.95Cs0.05Pb(I0.83Br0.17)3 (CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI x Cl y Br z during annealing, leading to high-quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing-incidence wide-angle X-ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large-scale production.
A sputtered NiO x seed layer is employed to promote the adsorption of [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) self-assembled monolayers. The resulting high-density MeO-2PACz provides an increased passivation, an enhanced hole-selectivity, a favorable energy-level alignment, and a robust physical contact between perovskite and indium tin oxide. The corresponding inverted perovskite solar cell exhibits an impressive efficiency of 19.9%.
Self-assembled monolayers (SAMs) have emerged as effective carrier transport layers in perovskite (PVK) solar cells because of their unique ability to manipulate interfacial property, as well as simple processing and scalable fabrication. However, the defects and pinholes derived from their sensitive adsorption process inevitably deteriorate the final device performance. Herein, a sputtered nickel oxide (NiO x ) interlayer is used as a seed layer to promote the adsorption of the [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz) SAM on the indium tin oxide (ITO) substrate. The promoted adsorption is attributed to the enhanced tridentate binding between MeO-2PACz and NiO x relative to the conventional bidentate binding between MeO-2PACz and ITO. In addition, the NiO x modification can simultaneously improve the passivation ability and hole-selectivity of the MeO-2PACz, provide a favorable energy-level alignment at the ITO/PVK interface, and prevent a direct contact between PVK and ITO. As a consequence, this NiO x -seeded MeO-2PACz hole transport layer enables a significantly enhanced power conversion efficiency of 19.9% in comparison with 18.4% of the control device. This work provides an effective strategy to improve the performance of the SAM-based photoelectric device.
A multifunctional surface design with the dense, stable, and crystalline-like 1H,1H,2H,2H-perfluorodecanethiol array is developed and applied onto the perovskite film and metal electrode. This strategy is demonstrated to not only impart the passivation effect and hydrophobic feature but also to suppress lead leakage via a synergy effect. Consequently, it facilitates the realization of stable and eco-friendly perovskite solar cells.
Environment-related degradation and lead leakage in perovskite solar cells have posed a big challenge for their commercialization. Here, design of superhydrophobic surfaces is demonstrated as an effective strategy toward these issues, in which thiol-functionalized perfluoroalkyl molecules are employed to chemically modify the lead halide perovskite film and metal electrode via a vapor-assisted self-assembly process. Due to the van der Waals forces, the generation of self-assembly monolayer prefers to pack in a dense way, resulting in the formation of a closest-packed, crystalline-like molecular array. This dense array is endowed with a low-surface-energy chemistry that can not only enhance the water and oxygen resistance of the completed device but also reduce the defect density on the perovskite surfaces. These merits eventually boost the efficiency of inverted perovskite solar cells up to 21.79% along with a substantially improved long-term stability. More importantly, the thiol-functionalized superhydrophobic array can immobilize most of the undercoordinated lead ions on the perovskite surfaces by metal-thiol coordination effect, which results in suppressing the lead leakage from the water-soluble lead halide perovskites. Therefore, an avenue is pointed out here to fabricate stable perovskite solar cells with reducing lead leakage, representing a substantial step toward practical applications.
This study mainly focuses on using the novel additive of N-methyl-2-pyrrolidone iodide to effectively conquer the uncontrollable crystallization kinetics during the CsPbI3 film deposition process. Importantly, the morphologies, phase purity, photoproperties, and carrier behavior of CsPbI3 in different dimensions are improved. Meanwhile, a record power conversion efficiency for quasi-2D (n = 20) CsPbI3 of 14.59% is obtained with negligible hysteresis and strengthened stability.
2D perovskite (PEA)2(Cs) n −1Pb n I3 n +1 (PEA: phenylethylammonium) exhibits more strengthened phase stability than its 3D components under ambient conditions and hence gained great attention in recent years. However, uncontrollable crystallization kinetics in (PEA)2(Cs) n −1Pb n I3 n +1 leads to difficulty in controlling film morphology and phase-orientation regulation, resulting in poor power conversion efficiency (PCE). Herein, by incorporating precursor additive N-methyl-2-pyrrolidone iodide (NMPI), the crystallization rate during the deposition of (PEA)2(Cs) n −1Pb n I3 n +1 film is efficiently regulated. As a result, the 2D or quasi-2D perovskite solar cell (PSC) delivers record PCEs in all reported 2D or quasi-2D CsPbX3 families, for instance, the quasi-2D (n = 20) CsPbI3 PSC exhibits a record PCE of 14.59%, showing significantly enhanced stability. Detailed characterization reveals that the NMPI forms hydrogen bonds with dimethylammonium iodide (DMAI) in the precursor to control crystallization rate for a smooth morphology with small fluctuation, which leads to improved carrier lifetime and reduced trap-density. More importantly, femtosecond transient absorption (fs-TA) measurements confirm an improved phase purity and the suppressed nonradiative recombination in quasi-2D perovskite film. It is believed that this simple additive strategy paves a new route for solving phase transition and crystallization kinetic problems in 2D and quasi-2D CsPbX3.
Self-polymerized monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) is incorporated into perovskite films by the antisolvent additive engineering, attributing to uniform composition distribution, improved crystallinity, and phase stability. Meanwhile, the defects density and recombination is reduced due to the strong interactions with DMAEMA. Finally, the high performance and stability perovskite solar cells are achieved.
While there is promising achievement in terms of the power conversion efficiency (PCE) of perovskite solar cells (PSCs), long-term stability has been considered the main obstacle for their practical application. In this work, the authors demonstrate the small monomer 2-(dimethylamino) ethyl methacrylate (DMAEMA) with unsaturated carboxylic acid ester bond in the antisolvent for perovskite formation to improve the PCE and stability. The results show that DMAEMA is self-polymerized and uniformly distributed in the film, contributing to the improved crystallinity of the perovskites. Equally important, it is found that there are newly established interactions of Pb2+ and DMAEMA, and iodine and ternary amine between DMAEMA and perovskites, which improves the uniformity of the lead (II) iodide vertical distribution along with the films and thus phase stability, as well as largely decreases defects density in the film. Overall, the inverted PSCs with DMAEMA exhibit a open-circuit voltage of 1.10 V, short-circuit current of 23.86 mA cm−2, fill factor of 0.82, and finally PCE reaches 21.52%. Meanwhile, the PSC stability is significantly improved due to the inhibition of the formation of iodine, reduction of the uncoordinated Pb2+, and suppression of phase segregation.
A-site deficient perovskite Li0.1La0.3NbO3 is designed as the anode for Li+ storage, exhibiting high reversible capacity, safe operating potential, excellent rate, and cycling performance. The maximum volume change is only 1.17%, showing a low strain characteristic. The fast Li+ transport pathways with external → grain boundaries → lattice deficiencies are demonstrated, which leads to excellent electrochemical performance.
The oxide perovskite family holds great promise for diverse applications on account of their unique chemical and physical properties. However, owing to the inadequate Li+-storage sites, the insertion-type perovskite anodes for lithium-ion batteries (LIBs) are limited. A-site deficient perovskites with rich intrinsic vacancies and ion transport channels are believed to be the desirable hosts of superior Li+ storage. Herein, the perovskite Li0.1La0.3NbO3 (LLNO) is designed and demonstrated as the remarkable anode for LIBs with a high specific capacity, a safe operating voltage, an excellent rate performance, and a long cycling life. More importantly, the outstanding cycling stability of LLNO is originated from its low strain characteristic with a maximum volume change of only 1.17%. The exceptional rate performance can be explained by the unconventional Li+ transport pathways with external → grain boundaries → lattice deficiencies. These results not only reveal that A-site deficient perovskite LLNO is a promising anode for LIBs but also provide fundamental insights into the Li+ ions transport mechanism, facilitating the development of high-performance perovskite anodes.
The electron transport layer (ETL) plays a crucial part in extracting electrons and optimizing interfacial contact for perovskite solar cells (PVSCs). Herein, the EVA is introduced into PC61BM to promote the orderly molecular stacking of ETLs. The PC61BM:EVA-based MAPbI3 PVSCs deliver a champion efficiency of 19.32% and regain 80% of initial efficiency after storage under 52% humidity for 1500 h.
The electron transport layer (ETL) plays a crucial part in extracting electron carriers while optimizing the interfacial contact of perovskite/electrode in planar heterojunction perovskite solar cells (PVSCs). Despite various ETLs being designed for efficient PVSCs, there exists hardly any research on the effect of molecular stacking order on device performance. Herein, poly(ethylene-co-vinyl acetate) (EVA) is employed as the [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) solution additive. The strong binding energy between EVA with PC61BM promotes the molecular stacking order of ETLs, which alleviates the morphology inhomogeneity, possesses a matched energy level, blocks ion migration, and improves the water–oxygen barrier of perovskite devices. The blade-coated MAPbI3-based PVSCs achieve a power conversion efficiency (PCE) of 19.32% with positive reproducibility and negligible hysteresis, as well as maintain 90% and 80% of the initial PCE after storage under inert and ambient conditions (52% humidity) for 1500 h without encapsulation. This strategy also improves the champion PCE of CsFAMA-based PVSCs to 20.33%. These findings demonstrate that the regulation of molecular stacking order is a valid approach to optimize interfacial charge-carrier recombination in PVSCs, which meet the demand for high-performance ETL in large-area PVSCs and improve the upscaling of the fabrication technology toward practical applications.
Publication date: 15 December 2021
Source: Joule, Volume 5, Issue 12
Author(s): Yanxun Li, Jianwei Ding, Cheng Liang, Xuning Zhang, Jianqi Zhang, Devon S. Jakob, Boxin Wang, Xing Li, Hong Zhang, Lina Li, Yingguo Yang, Guangjie Zhang, Xiaoxian Zhang, Wenna Du, Xinfeng Liu, Yuan Zhang, Yong Zhang, Xiaoji Xu, Xiaohui Qiu, Huiqiong Zhou
Two novel dopant-free hole transport materials (HTMs) named Y6-T and Y-T with a large conjugated electron-deficient core are developed for efficient perovskite solar cells. The champion power conversion efficiency (PCE) reaches 20.29% for Y-T-based device. The Y-T-based devices without encapsulation retain over 90% of the initial PCE in air with a relative humidity around 30% after storing for 60 days.
Hole transport materials (HTMs) play a significant role in device efficiencies and long-term stabilities of perovskite solar cells (PSCs). In this work, two simple dopant-free HTMs are designed with a large conjugated electron-deficient core. On the one hand, a large coplanar backbone endows enhanced π–π stacking and reduced hole hopping distance. On the other hand, the incorporation of electron-deficient unit can easily tune the energy levels as well as increase hole mobilities. Combining these two advantages together, 12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro[1,2,5]thiadiazole[3,4-e]thieno[2″,3″:4,5]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole is chosen as the large electron-deficient core to construct two novel dopant-free HTMs, Y6-T and Y-T. Both Y6-T and Y-T behave suitable highest occupied molecular orbital levels, good hole mobilities, as well as strong hydrophobicities. After careful device optimization with a passivation agent, Y-T delivers an impressive power conversion efficiency of 20.29%, which is higher than that of Y6-T (18.82%) and doped spiro-OMeTAD (19.24%). Moreover, PSCs based on Y6-T and Y-T show much better long-term stabilities than spiro-OMeTAD due to the intrinsic hydrophobicity. Therefore, this work provides a promising candidate as well as a useful design strategy for exploring dopant-free HTMs, which may pave the way for the commercialization of PSCs.
Thermal-aged precursor solution (TAPS) featuring the aggregated colloidal clusters with fewer nucleation sites is applied to fabricate high-quality quasi-2D perovskite films, through which a record-high V OC of 1.24 V is achieved in (AA)2MA4Pb5I16-based quasi-2D perovskite solar cells, leading to a champion efficiency of 18.68%.
Quasi-2D perovskites have received wide attention in photovoltaics owing to their excellent materials robustness and merits in the device stability. However, the highest power conversion efficiency (PCE) reported on quasi-2D perovskite solar cells (PSCs) still lags those of the 3D counterparts, mainly caused by the relatively high voltage loss. Here, a study is presented on the mitigation of voltage loss in quasi-2D PSCs via usage of thermal-aged precursor solutions (TAPSs). Based on the (AA)2MA4Pb5I16 (n = 5) quasi-2D perovskite absorber with a bandgap of ≈1.60 eV, a record-high open-circuit voltage of 1.24 V is obtained, resulting in boosting the PCE to 18.68%. The enhanced photovoltaic performance afforded by TAPS is attributed to the thermal-aged solution processing that triggers colloidal aggregations to reduce the nucleation sites inside the solution. As a result, formation of high-quality perovskite films featuring compact morphology, preferential crystal orientation, and lowered trap density is allowed. Of importance, with the improved film quality, the corrosion of Ag electrode induced by ion migrations is effectively restrained, which leads to a satisfactory storage stability with <2% degradation after 1200 h under nitrogen environment without encapsulation.
A polyoxometalate-based material CoW12@MIL-101(Cr) is applied as an effective dopant to eliminate Pb0, passivate Pb2+ defects, and speeds up the volatilization of organic solvents during the crystallization of perovskite, resulting in a uniform and dense perovskite film. The doped device demonstrates an enhanced power conversion efficiency of 21.39% and excellent humid and thermal stability.
The high-quality perovskite film with few defects plays an important role in the power conversion efficiency (PCE) and long-term stability of perovskite solar cells. Here, an efficient strategy is proposed to eliminate Pb0 and passivate Pb2+ simultaneously by employing a stable polyoxometalate-based material CoW12@MIL-101(Cr) in the precursor solution of perovskite. The controllable oxidation ability of CoW12 is optimized through the interaction with metal–organic frameworks, resulting in a doped perovskite film with regular morphology, large grain size, and low defects density. The solvent effects and formation of intermediate materials in the precursor solution are further investigated by an in situ thermogravimetry-Fourier transform infrared spectroscopy analysis. In addition, the champion doped-device showed enhanced PCE to 21.39% and excellent stability, maintaining 85% and 89% of the original PCE after heating at 85 °C in N2 atmosphere and stored in ambient conditions (25 °C, 40% humidity) for 1000 h, respectively.
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A new morphology control approach is developed to fabricate high-performance organic solar cells by utilizing the synergistic effect of 1-chloronaphthalene (CN) and dithieno[3,2-b:2′,3′-d]thiophene (DTT) additives. This approach exhibits general application in various active layer systems to achieve well-developed morphology, enabling outstanding power-conversion efficiency over 18.8% and fill factor exceeding 80% for the device based on PTQ10:m-BTP-PhC6:PC71BM.
Controlling the self-assembling of organic semiconductors to form well-developed nanoscale phase separation in the bulk-heterojunction active layer is critical yet challenging for building high-performance organic solar cells (OSCs). Particularly, the similar anisotropic conjugated structures between nonfullerene acceptors and p-type organic semiconductor donors raise more complexity on manipulating their aggregation toward appropriate phase separation. Herein, a new approach to tune the morphology of photoactive layer is developed by utilizing the synergistic effect of dithieno[3,2-b:2′,3′-d]thiophene (DTT) and 1-chloronaphthalene (CN). The volatilizable solid additive DTT with high crystallinity can restrict the over self-assembling of nonfullerene acceptors during the film casting process, and then allowing the refining of phase separation and molecular packing with the simultaneous volatilization of DTT under thermal annealing. Consequently, the PTQ10:m-BTP-PhC6:PC71BM-based ternary OSCs processed by the dual additives of CN and DTT record a notable power-conversion efficiency of 18.89%, with a remarkable FF of 80.6%.
