Constructing low-dimensional/three-dimensional (LD/3D) perovskite solar cells can improve efficiency and stability. However, the design and selection of LD perovskite capping materials are incredibly scarce for inverted perovskite solar cells (PSCs) because LD perovskite capping layers often favor hole extraction and impede electron extraction. Here, we develop a facile and effective strategy to modify the perovskite surface by passivating the surface defects and modulating surface electrical properties by incorporating morpholine hydriodide (MORI) and thiomorpholine hydriodide (SMORI) on the perovskite surface. Compared with the PI treatment that we previously developed, the one-dimensional (1D) perovskite capping layer derived from PI is transformed into a two-dimensional (2D) perovskite capping layer (with MORI or SMORI), achieving dimension regulation. It is shown that the 2D SMORI perovskite capping layer induces more robust surface passivation and stronger n-N homotype 2D/3D heterojunctions, achieving a p-i-n inverted solar cell with an efficiency of 24.55%, which retains 87.6% of its initial efficiency after 1500 h of operation at the maximum power point (MPP). Furthermore, 5 × 5 cm2 perovskite mini-modules are presented, achieving an active-area efficiency of 22.28%. In addition, the quantum well structure in the 2D perovskite capping layer increases the moisture resistance, suppresses ion migration, and improves PSCs' structural and environmental stability.
Dopant‐free hole transport layers (HTLs) play a crucial role in achieving high‐efficiency and stable perovskite solar cells (PSCs). However, only a limited number of these HTLs have demonstrated power conversion efficiencies (PCEs) surpassing 21%. Herein, the design and synthesis of two polymeric HTLs with a novel DA’D–A backbone are presented. The incorporation of two A units (benzothiazole and imide functionalized aromatics) in the polymer imparts a rigid backbone, high mobility, appropriate film morphology, excellent thermal stability, and a deeper highest occupied molecular orbital energy level, crucial for achieving a more suitable energy‐level alignment between HTL and perovskite layer. Notably, the champion PSC based on our HTLs exhibits a remarkable PCE of 22.02% with minimal hysteresis and excellent thermal stability, surpassing the performance of devices based on the benchmark polymeric HTL PTAA under identical conditions. These findings underscore the immense potential of our DA’D‐A backbone strategy in developing high‐performance dopant‐free polymer HTLs for enhancing the PCE of PSCs.
Inverted perovskite solar cells (PSCs) are preferred for tandem applications due to their superior compatibility with diverse bottom solar cells. However, the solution processing and low formation energy of perovskites inevitably lead to numerous defects at both the bulk and interfaces. We report a facile and effective strategy for precisely modulating the perovskite by incorporating AlOx deposited by atomic layer deposition (ALD) on the top interface. We find that Al3+ can not only infiltrate the bulk phase and interact with halide ions to suppress ion migration and phase separation but also regulate the arrangement of energy levels and passivate defects on the perovskite surface and grain boundaries. Additionally, ALD-AlOx exhibits an encapsulation effect through a dense interlayer. Consequently, the ALD-AlOx treatment can significantly improve the power conversion efficiency (PCE) to 21.80 % for 1.66 electron volt (eV) PSCs. A monolithic perovskite-silicon TSCs using AlOx-modified perovskite achieved a PCE of 28.5 % with excellent photothermal stability. More importantly, the resulting 1.55 eV PSC and module achieved a PCE of 25.08 % (0.04 cm2) and 21.01 % (aperture area of 15.5 cm2), respectively. Our study provides an effective way to efficient and stable wide-band gap perovskite for perovskite-silicon TSCs and paves the way for large-area inverted PSCs.
Dopant-free polymer hole transport materials (HTMs) exhibit high thermal stability, hydrophobicity and filmprocessing capabilities, demonstrating excellent device efficiency and stability in perovskite solar cells (PSCs). Continued innovation of wide-bandgap polymers in organic photovoltaics (OPV) provides a valuable toolbox for developing polymeric HTMs. Here, we propose an effective molecule design for selecting structurally relevant polymers (D18, D18-Cl, PBQx-TCl) available for commercialization. We discover that the highly planar conjugated backbones play a crucial role in regulating the packing orientation of the film relative to the perovskite. The moderate aggregation with face-on packing orientation is conducive to the high-quality film, which is responsible for better contact with perovskite and superior charge extraction and transport. Simultaneously, these polymers with robust passivation enhanced the open circuit voltage (V-OC) without additional passivation layers, streamlining the device process. Consequently, a PSC using dopant-free PBQx-TCl HTL demonstrated an efficiency of 24.12 % with a high VOC of 1.20 V and good operational stability (T-90 > 600 h). This work reveals transparent structure-function-performance relationships between molecules and devices, paving the way for the subsequent development of high-performance HTMs.
The hygroscopic dopants used in Spiro‐OMeTAD hole‐transport materials (HTMs) in n–i–p perovskite solar cells (PSCs) inevitably cause device degradation. Herein, two polymer interface materials based on lead anchoring groups are developed. It is found that 2D polymers 2DP‐BT and 2DP‐Por can form dense films and exhibit excellent hydrophobicity. Importantly, 2DP‐Por can passivate the surface defects through noncovalent interactions, reducing nonradiative recombination loss. After introducing these polymer interface materials between the perovskite layer and the HTM layer, the optimized devices using 2DP‐Por and 2DP‐BT achieve champion power conversion efficiency of 24.12% and 23.29%, respectively, and the stability is significantly improved. These results indicate that developing polymer interface materials containing lead anchoring groups can improve PSC efficiency and stability and elucidate critical molecular design rules for interface materials.
To maximize the power conversion efficiency (PCE) and stability of perovskite/silicon tandem solar cells (TSCs), high‐performance and stable perovskite top cells with wide‐bandgaps are required. A 2D/3D wide‐bandgap perovskite with a bandgap of 1.69 eV using 1H‐1,2,4‐triazole‐1‐carboximidamide (1‐TzFACl) as a spacer is developed. The 2D/3D wide‐bandgap perovskite shows better film quality, enhanced crystallinity, suppressed nonradiative recombination, and significantly improved phase stability. Its initial PCE (21.58%) remains above 87% after 1560 h of continuous illumination due to the insertion of Cl − in the perovskite lattice. A monolithic two‐terminal perovskite/silicon TSC achieves a PCE of 25.66% with high light stability. This work provides an ingenious strategy to restrain the phase segregation in wide‐bandgap perovskites, leading to effective and stable perovskite/silicon TSCs.
A considerable efficiency gap exists between large-area perovskite solar modules and small-area perovskite solar cells. The control of forming uniform and large-area film and perovskite crystallization is still the main obstacle restricting the efficiency of PSMs. In this work, we adopted a solid–liquid two-step film formation technique, which involved the evaporation of a lead iodide film and blade coating of an organic ammonium halide solution to prepare perovskite films. This method possesses the advantages of integrating vapor deposition and solution methods, which could apply to substrates with different roughness and avoid using toxic solvents to achieve a more uniform, large-area perovskite film. Furthermore, modification of the NiO x /perovskite buried interface and introduction of Urea additives were utilized to reduce interface recombination and regulate perovskite crystallization. As a result, a large-area perovskite film possessing larger grains, fewer pinholes, and reduced defects could be achieved. The inverted PSM with an active area of 61.56 cm 2 (10 × 10 cm 2 substrate) achieved a champion power conversion efficiency of 20.56% and significantly improved stability. This method suggests an innovative approach to resolving the uniformity issue associated with large-area film fabrication.
The dielectronic constant of organic semiconductor materials is directly related to its molecule dipole moment, which can be used to guide the design of high-performance organic photovoltaic materials. Herein, two isomeric small molecule acceptors, ANDT-2F and CNDT-2F, are designed and synthesized by using the electron localization effect of alkoxy in different positions of naphthalene. It is found that the axisymmetric ANDT-2F exhibits a larger dipole moment, which can improve exciton dissociation and charge generation efficiencies due to the strong intramolecular charge transfer effect, resulting in the higher photovoltaic performance of devices. Moreover, PBDB-T:ANDT-2F blend film exhibits larger and more balanced hole and electron mobility as well as nanoscale phase separation due to the favorable miscibility. As a result, the optimized device based on axisymmetric ANDT-2F shows a J(SC) of 21.30 mA cm(-2), an FF of 66.21%, and a power conversion energy of 12.13%, higher than that of centrosymmetric CNDT-2F-based device. This work provides important implications for designing and synthesizing efficient organic photovoltaic materials by tuning their dipole moment.
The super-white body might be defined as its reflectivity exceeding 98% at any angle in the visible light spectrum, which can be used in a variety of emerging fields including optics, energy, environment, aerospace, etc. However, elaborate synthesis of a light-weight, highly reflective super-white aerogel body remains a great challenge. In this work, fine-tuning of silica aerogel co-hydrolyzed precursor ratios, 99.7% reflectivity with angle-independence in the visible light spectrum has been successfully achieved when the areal density is only 0.129 g cm-2 , which breaks through the theoretical bandwidth limit of photonic crystals as well as the measured reflectivity limit of conventional porous materials. Furthermore, the reflectivity of super-white silica aerogel remains unchanged after various harsh deformations including compression and bending 1000 times, solar (≈800 W m-2 ), ultraviolet (≈0.68 W m-2 ), and humidity (100%) aging for 100 days, liquid nitrogen (-196 °C) and high-temperature (300 °C) thermal shock 100 times. As proofs of performance, the resulting super-white silica aerogels have been used as the novel standard white plate for better spectrum calibration, as the flexible projector curtains for optical display, as well as the transmitted light reflective layer in the photovoltaic cell for improving the relative power conversion efficiency of 5.6%.
The pursuit of efficient CO2 capture materials remains an unmet challenge. Especially, meeting both high sorption capacity and fast uptake kinetics is an ongoing effort in the development of CO2 sorbents. Here, a strategy to exploit liquid-in-aerogel porous composites (LIAPCs) that allow for highly effective CO2 capture and selective CO2 /N2 separation, is reported. Interestingly, the functional liquid tetraethylenepentamine (TEPA) is partially filled into the air pockets of SiO2 aerogel with left permanent porosity. Notably, the confined liquid thickness is 10.9-19.5 nm, which can be vividly probed by the atomic force microscope and rationalized by tailoring the liquid composition and amount. LIAPCs achieve high affinity between the functional liquid and solid porous counterpart, good structure integrity, and robust thermal stability. LIAPCs exhibit superb CO2 uptake capacity (5.44 mmol g-1 , 75 °C, and 15 vol% CO2 ), fast sorption kinetics, and high amine efficiency. Furthermore, LIAPCs ensure long-term adsorption-desorption cycle stability and offer exceptional CO2 /N2 selectivity both in dry and humid conditions, with a separation factor up to 1182.68 at a humidity of 1%. This approach offers the prospect of efficient CO2 capture and gas separation, shedding light on new possibilities to make the next-generation sorption materials for CO2 utilization.
Developing dopant‐free hole transport materials (HTMs) to replace Spiro‐OMeTAD is a challenging but urgent issue for commercialization of state‐of‐the‐art n‐i‐p structured perovskite solar cells (PSCs). Here, this work proposes an effective two‐dimensional conjugate engineering strategy to tune molecular stacking orientation and improve the hole mobility of dopant‐free small molecule HTMs. For the first time, triphenylamine (TPA) groups are incorporated as side chains of benzo [1,2‐b:4,5‐b′]dithiophene (BDT) unit to extend the longitudinal conjugate, achieving two donor‐acceptor‐acceptor type 2D small molecules, namely XF2 and XF3, which show a dominant face‐on orientation and better hole transport mobility than the linear small molecule XF1. The incorporation of alkoxy Lewis base groups makes XF3 a more effective defect passivator for perovskite surfaces. As a result, the PSCs using pristine XF3 HTM show a dramatically improved efficiency of 20.59% along with improved long‐term stability compared to that of XF1 HTM (power conversion efficiency (PCE) = 18.84%). A champion efficiency of 21.44% is achieved through device engineering for dopant‐free XF3‐based PSCs. The results show that the building block with longitudinal conjugate extension in small molecules plays an essential role in the face‐on orientation morphology and elucidates a key design rule for the dopant‐free small molecule HTMs for high‐performance PSCs.
Aerogels are ultralight solid materials with three‐dimensional interconnected porous structures that offer considerable advantages for various protective applications. Lasers have led to various technological revolutions in aerospace, medical science, and industrial manufacturing. However, shielding against high‐energy laser irradiation using aerogels has rarely been reported. A super‐white (reflectivity >98%) boron nitride (BN) aerogel constructed using BN nanoribbons is developed in this study for high‐energy laser protection. Large numbers of BN nanoribbons serve as randomized and disordered optical nanobarriers for intense backlight scattering, which contribute to high broadband reflectivity. Combined with the low thermal conductivity of the aerogel structure and the excellent high‐temperature stability of BN, the resulting BN aerogel exhibits a high protective threshold of 2.1 × 10 4 W cm −2 . Moreover, the BN aerogel possesses a soft porous network and a low thermal expansion coefficient, which is promising for tolerating the thermal stress and shock of local high‐temperature fields caused by laser irradiation. The successful laser shielding by the super‐white BN aerogel may be helpful for designing and fabricating advanced aerogel‐based lightweight anti‐laser materials.
The buried interface in perovskite solar cells (PSCs) is pivotal for achieving high efficiency and stability. However, it is challenging to study and optimize the buried interface due to its non-exposed feature. Here, a facile and effective strategy is developed to modify the SnO2/perovskite buried interface by passivating the buried defects in perovskite and modulating carrier dynamics via incorporating formamidine oxalate (FOA) in SnO2 nanoparticles. Both formamidinium and oxalate ions show a longitudinal gradient distribution in the SnO2 layer, mainly accumulating at the SnO2/perovskite buried interface, which enables high-quality upper perovskite films, minimized defects, superior interface contacts, and matched energy levels between perovskite and SnO2. Significantly, FOA can simultaneously reduce the oxygen vacancies and tin interstitial defects on the SnO2 surface and the FA(+)/Pb2+ associated defects at the perovskite buried interface. Consequently, the FOA treatment significantly improves the efficiency of the PSCs from 22.40% to 25.05% and their storage- and photo-stability. This method provides an effective target therapy of buried interface in PSCs to achieve very high efficiency and stability.
Charge carrier nonradiative recombination (NRR) caused by interface defects and nonoptimal energy level alignment is the primary factor restricting the performance improvement of perovskite solar cells (PSCs). Interfacial modification is a vital strategy to restrain NRR and enable high-performance PSCs. We report here two interfacial materials, PhI-TPA and BTZI-TPA, consisting of phthalimide and a 2,1,3-benzothiadiazole-5,6-dicarboxylicimide core, respectively. The difunctionalized BTZI-TPA with imide and thiadiazole shows higher hole mobility, better aligned energy levels, and stronger interaction with uncoordinated Pb2+ on the perovskite surface, suppressing NRR and carrier accumulation at the interface of perovskite/spiro-OMeTAD and yielding enhanced open-circuit voltage and fill factor. Consequently, the PSC based on BTZI-TPA delivers a high efficiency of 24.06% with an excellent fill factor of 83.10%, superior to that (21.47%) of the reference cell without an interfacial layer, and 21.45% efficiency for the device with a scaled-up area (1.00 cm2). These results underscore the potential of imide and thiadiazole groups in developing interfacial layers with strong passivation capability, effective charge transport property, and fine-tuned energetics for stable and efficient PSCs.
Solution-processed hole contact materials, as an indispensable component in perovskite solar cells (PSCs), have been widely studied with consistent progress achieved. One bottleneck for the commercialization of PSCs is the lack of hole contact materials with high performance, cost-effective preparation, and green-solvent processability. Therefore, the development of versatile hole contact materials is of great significance. Herein, we report two novel donor- acceptor (D-A)-type hole contact molecules (FMPA-BT-CA and 2FMPA-BT-CA) with low cost and alcohol-based processability by utilizing a fluorination strategy. We showed that the fluorine atoms lead to the lowered highest occupied molecular orbital (HOMO) energy levels and larger dipole moments for FMPA- BT-CA and 2FMPA-BT-CA. Moreover, fluorination also improves the buried interfacial interaction between hole contacts and perovskite. As a result, a remarkable power conversion efficiency (PCE) of 22.37% along with good light stability could be achieved for green-solvent-processed FMPA-BT-CA-based inverted PSC devices, demonstrating the great potential of environmentally compatible hole contacts for highly efficient PSCs.
>Bulk-heterojunction polymer solar cells(PSCs) as a clean and renewable energy resource have attracted great attention from both academia and industry [1-20] . Recently nonfullerene PSCs based on polymer donors(PDs) and small molecule acceptors(SMAs) have achieved remarkable success with the power conversion efficiencies(PCEs) over 18% [21-26] .
A bidentate ligand 1,10-phenanthroline enables a green-solvent-processable low-cost hole-transport materialM1, which efficiently passivates the Pb2+ion defects of perovskite toward high-performance inverted perovskite solar cells.
Silica aerogels with accurate building-block control are realized by adjusting the surfactant concentration during the synthesis process. The resulting silica-aerogel monolith with spherical building blocks of ≈24-40 nm, together with a deliberately created hole along the incident light direction, shows an incredibly promising application in monochromatic laser-driven lighting. The resulting coefficient of illuminance variation is as low as 8.1%, significantly outperforming commercially available ground-glass diffusers (139.0%) and polymer diffusers (249.1%); the speckle contrast is lower, as well as better, than that can be recognized by the human eye (4%), and the illuminance uniformity in the range of 0.770-0.862 is much better (higher) than that indoor workplace lighting required by the International Organization for Standardization. Lighting with any color in the visible spectrum, including white, can be obtained by using three primary color lasers (450, 532, and 638 nm) with different powers simultaneously as the light source. The resulting silica aerogel, which has excellent thermal stability, high laser-damage threshold, outstanding mechanical performance, and superhydrophobicity, can be further applied to long-distance and noncontact laser-driven lighting in rain or underwater without any additional encapsulation components.
Two-dimensional (2D) perovskites are emerging photovoltaic materials because of their highly tunable photophysical properties and improved environmental stability in comparison with 3D perovskites. Here, a thiophene-based bulky dication spacer, namely, 2,5-thiophenedimethylammonium (ThDMA), was developed and applicated in 2D Dion-Jacobson (DJ) perovskite. High-quality 2D DJ perovskite, (ThDMA)(MA)n-1PbnI3n+1 (nominal n = 5), with improved crystallinity, preferred vertical orientation, and enlarged spatially resolved carrier lifetime could be achieved by a one-step method using a mixed solvent of DMF/DMSO (v/v, 9:1). The optimized device exhibits a high efficiency of 15.75%, which is a record for aromatic spacer-based 2D DJ perovskite solar cells (PSCs). Moreover, the unencapsulated 2D DJ perovskite devices sustained over 95% of their original efficiency after storage in N2 for 1655 h. Importantly, both the light-soaking stability and thermal stability (T = 80 °C) of the 2D DJ perovksite devices are dramatically improved in comparison with their 3D counterparts. These results indicate that highly efficient and stable 2D DJ PSCs could be achieved by developing thiophene-based aromatic spacers as well as device engineering.
An efficiency of 21.31% was achieved with enhanced stability for a mixed HTM-based device because of the high hole mobility, low reorganization energy and surface passivate effect of the DRSBDT-2OT component.