Metal halide perovskite solar cells have demonstrated a high power conversion efficiency (PCE), and further enhancement of the PCE requires a reduction of the bandgap-voltage offset (WOC) and the ...non-radiative recombination photovoltage loss (ΔVOC,nr). Here, we report an effective approach for reducing the photovoltage loss through the simultaneous passivation of internal bulk defects and dimensionally graded two-dimensional perovskite interface defects. Through this dimensionally graded perovskite formation approach, an open-circuit voltage (VOC) of 1.24 V was obtained with a champion PCE of 21.54% in a 1.63 eV perovskite system (maximum VOC = 1.25 V, WOC = 0.38 V and ΔVOC,nr = 0.10 V); we further decreased the WOC to 0.326 V in a 1.53 eV perovskite system with a VOC of 1.21 V and a PCE of 23.78% (certified 23.09%). This approach is equally effective in achieving a low WOC (ΔVOC,nr) in 1.56 eV and 1.73 eV perovskite solar cell systems, and further leads to the substantially improved operational stability of perovskite solar cells.The use of a dimensionally graded 2D perovskite interface and passivation results in perovskite solar cells with very low photovoltage loss.
Epitaxial growth gives the highest‐quality crystalline semiconductor thin films for optoelectronic devices. Here, a universal solution‐processed bottom‐up quasi‐epitaxial growth of highly oriented ...α‐formamidinium lead triiodide (α‐FAPbI3) perovskite film via a two‐step method is reported, in which the crystal orientation of α‐FAPbI3 film is precisely controlled through the synergetic effect of methylammonium chloride and the large‐organic cation butylammonium bromide. In situ GIWAXS visualizes the BA‐related intermediate phase formation at the bottom of film, which serves as a guiding template for the bottom‐up quasi‐epitaxial growth in the subsequent annealing process. The template‐guided epitaxially grown BAFAMA perovskite film exhibits increased crystallinity, preferred crystallographic orientation, and reduced defects. Moreover, the BAFAMA perovskite solar cells demonstrate decent stability, maintaining 95% of their initial power conversion efficiency after 2600 h ambient storage, and 4‐time operation condition lifetime enhancement.
A universal solution‐processed bottom‐up quasi‐epitaxial growth of highly oriented α‐FAPbI3 perovskite film is achieved through the synergetic effect of methylammonium chloride and a large‐organic cation. In situ GIWAXS visualizes the BA‐related intermediate phase formation at the bottom, which serves as a guiding template for the bottom‐up quasi‐epitaxial growth in the subsequent annealing process.
Interstitial iodides are the most critical type of defects in perovskite solar cells that limits efficiency and stability. They can be generated during solution, film, and device processing, further ...accelerating degradation. Herein, we find that introducing a small amount of a zinc salt- zinc trifluoromethane sulfonate (Zn(OOSCF
)
) in the perovskite solution can control the iodide defects in resultant perovskites ink and films. CF
SOO
vigorously suppresses molecular iodine formation in the perovskites by reducing it to iodide. At the same time, zinc cations can precipitate excess iodide by forming a Zn-Amine complex so that the iodide interstitials in the resultant perovskite films can be suppressed. The perovskite films using these additives show improved photoluminescence quantum efficiency and reduce deep trap density, despite zinc cations reducing the perovskite grain size and iodide interstitials. The zinc additives facilitate the formation of more uniform perovskite films on large-area substrates (78-108 cm
) in the blade-coating process. Fabricated minimodules show power conversion efficiencies of 19.60% and 19.21% with aperture areas of 84 and 108 cm
, respectively, as certified by National Renewable Energy Laboratory (NREL), the highest efficiency certified for minimodules of these sizes.
Boolean satisfiability problems (SAT) have very rich generic and domain-specific structures. How to capture these structural features in the embedding space and feed them to deep learning models is ...an important factor influencing the use of neural networks to solve SAT problems. Graph neural networks have achieved good results, especially for message-passing models. These capture the displacement-invariant architecture well, whether building end-to-end models or improving heuristic algorithms for traditional solvers. We present the first framework for predicting the satisfiability of domain-specific SAT problems using graph attention networks, GAT-SAT. Our model can learn satisfiability features in a weakly supervised setting, i.e., in the absence of problem-specific feature engineering. We test the model to predict the satisfiability of randomly generated SAT instances SR(N) and random 3-SAT problems. Experiments demonstrate that our model improves the prediction accuracy of random 3-SAT problems by 1–4% and significantly outperforms other graph neural network approaches on random SR(N). Compared to NeuroSAT, our model can almost always achieve the same or even higher accuracy with half the amount of iterations. At the end of the paper, we also try to explain the role played by the graph attention mechanism in the model.
Perovskite solar cells (PSCs) with a light‐harvesting three‐dimensional perovskite bulk layer as backbone component have achieved great progress in performance. Nonradiative recombination is one ...major place to improve efficiency and stability as they cause significant energy loss in PSCs. Additionally, an imperfection in grain boundaries will initiate device degradation. One of the most successful strategies to decrease nonradiative recombination in PSCs is the introduction of reduced dimensional perovskite (e.g., perovskite quantum wells), benefiting the device's efficiency and stability tremendously. Here, instead of quantum wells, mixed‐cation perovskites with ligand‐contained CsPbBrxI3 − x quantum dots (QDs) are prepared, which is shown to function as perovskite healing “surface patches.” Benefiting from the “surface patches” effect, the QDs‐film shows reduced defects and enhancing film quality which lead to the excellent performance of solar cells (enhancing the power conversion efficiency from 19.21% of the control device to 21.71% 22.1% in reverse scan).
Perovskite‐healing “surface patches” are developed by ligand‐contained CsPbIxBr3 − x quantum dots (QDs). Benefiting from the “surface patches” effect, the QDs‐film shows reduced defects and enhancing film quality which lead to the excellent performance of the solar cell.
The ligand-tailored SnO2 QDs ETL with multi-functional terminal groups in situ refines the buried interfaces with both the perovskite and transparent electrode via enhanced interface binding and ...perovskite passivation.
Abstract
The benchmark tin oxide (SnO
2
) electron transporting layers (ETLs) have enabled remarkable progress in planar perovskite solar cell (PSCs). However, the energy loss is still a challenge ...due to the lack of “hidden interface” control. We report a novel ligand-tailored ultrafine SnO
2
quantum dots (QDs)
via
a facile rapid room temperature synthesis. Importantly, the ligand-tailored SnO
2
QDs ETL with multi-functional terminal groups in situ refines the buried interfaces with both the perovskite and transparent electrode
via
enhanced interface binding and perovskite passivation. These novel ETLs induce synergistic effects of physical and chemical interfacial modulation and preferred perovskite crystallization-directing, delivering reduced interface defects, suppressed non-radiative recombination and elongated charge carrier lifetime. Power conversion efficiency (PCE) of 23.02% (0.04 cm
2
) and 21.6% (0.98 cm
2
,
V
OC
loss: 0.336 V) have been achieved for the blade-coated PSCs (1.54 eV
E
g
) with our new ETLs, representing a record for SnO
2
based blade-coated PSCs. Moreover, a substantially enhanced PCE (
V
OC
) from 20.4% (1.15 V) to 22.8% (1.24 V, 90 mV higher
V
OC
, 0.04 cm
2
device) in the blade-coated 1.61 eV PSCs system, via replacing the benchmark commercial colloidal SnO
2
with our new ETLs.
Formamidinium lead iodide (FAPbI3) perovskite is a front-runner material for efficient perovskite solar cells (PSCs) due to its high light-absorption coefficient, narrow band gap, and superior ...photostability and thermostability. High-quality FAPbI3 perovskite formation typically requires an >160°C annealing process to induce phase transition from the photoinactive yellow phase (δ-FAPbI3) to the photoactive black phase (α-FAPbI3). However, this high-temperature annealing can induce defects in the films and hinders application in flexible solar cells. Here, we report a facile method to fabricate high-quality α-FAPbI3 perovskite films at room temperature, without thermal annealing or vacuum-assisted processes. Combined computational and experimental results reveal the crystallization mechanism of α-FAPbI3 formation at room temperature. We demonstrate PSCs with a power-conversion efficiency of 19.09%, which is the highest efficiency for room temperature PSCs to the best of our knowledge. This study may offer a cost-effective way to fabricate highly efficient PSCs at room temperature.
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Method for fabricating α-FAPbI3 at room temperatureMechanism of the formation of α-FAPbI3 at room temperatureHighly efficient room temperature perovskite solar cellsUnique trend of PCE evolution in stability test
α-FAPbI3 is a front-runner perovskite material for highly efficient solar cells, although its preparation typically requires high-temperature annealing. Chen et al. report a facile method for fabricating high-quality α-FAPbI3 films at room temperature and reveal the mechanism of the formation of α-FAPbI3 through theoretical and experimental methods.
The best reported state-of-the-art perovskite solar cells (PSCs) show record power conversion efficiency (PCE) over 23%, where sequentially deposited formamidinium (FA)-dominated perovskites were ...adopted. Here, we develop a stabilizer-assisted growth method involving two stabilizers (MAPbBr3 and MACl) to fabricate phase-pure formamidinium lead iodide (α-FAPbI3) perovskite and substantially improve its opto-electronic properties. The high crystalline and large crystal grains within the α-FAPbI3 perovskite film as well as the reduced defects contribute to the enhanced PCE up to 22.51% in planar PSCs. More importantly, the stability of phase-stabilized FAPbI3 PSC is also significantly improved and the corresponding device exhibits an impressive 97% retention after 2600 h storage under ambient conditions. This work paves a way to further improve the photovoltaic performance and stability of FA-based planar PSCs.
We develop a stabilizer-assisted growth method involving two stabilizers (MAPbBr3and MACl) to fabricate phase-pure formamidinium lead iodide (α-FAPbI3) perovskite and substantially improve its opto-electronic properties. High-crystallized and enlarged crystal grains within the obtained α-FAPbI3 perovskite film as well as reduced defects contribute to boost the PCE up to 22.51% for the low-temperature processed planar PSCs. More importantly, the stability of phase-stabilized FAPbI3 PSC is also significantly improved and the corresponding device exhibits an impressive 97% retention after 2600-h storage under ambient conditions. Display omitted
•Our fabricated planar perovskite device show a high efficiency of 22.51% and a high stabilized PCE of 22.1%.•Significantly enhanced phase stability and long-term stability of FA-based PSCs.•Systematic investigation on the device performance and stability properties are performed.
Flexible photovoltaic devices are promising candidates for triggering the Internet of Things (IoT). However, the power conversion efficiencies (PCEs) of flexible organic photovoltaic (OPV) devices ...with high conductivity poly(3,4‐ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes on plastic are lagging behind the rigid devices due to the low transmittance of polyethylene terephthalate (PET)/PEDOT:PSS. Moreover, the poor stretchability of the commonly used plastic substrates largely hinders the practical application of wearable devices. Herein, a novel stretchable indium tin oxide (ITO)‐free OPV device with a surface‐texturing polydimethylsiloxane (PDMS) substrate for outdoor strong‐ and indoor dim‐light energy harvesting is reported. The high diffuse transmittance and haze effect of the substrate enable stretchable ITO‐free devices, yielding a high PCE of 15.3% under 1 sun illumination. More excitingly, the stretchable device based on textured PDMS/PEDOT:PSS maintains a comparable PCE of 20.5% (20.8% for the rigid device) under indoor light illumination. Notably, the stretchable device is much more insensitive to the light direction, maintaining 38.5% of the initial PCE at an extremely small incident angle of 10° (16.3% for glass/ITO‐based counterpart). The texturing stretchable substrate provides a new direction for achieving high performance and enhanced light utilization for the stretchable light‐harvesting device, suitable for indoor and outdoor applications.
A simple, generic, and effective approach toward high‐performance, stretchable outdoor and indoor organic photovoltaic is reported, and a high power conversion efficiency (PCE) of 15.3% under 1 sun illumination is achieved. Under indoor illumination, the stretchable device shows a comparable performance (20.5% vs 20.8%) to glass/indium tin oxide (ITO)‐based devices. The stretchable device shows a PCE 1.5–2 times larger than that of rigid devices at a large incident angle.
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