Chen Weijie

PCN-224 quantum dots (QDs) with abundant Lewis base groups are incorporated into perovskite layer and hole transport layer (HTL) of perovskite solar cells (PSCs). PCN-224 QDs enable strong coordination interaction with the under-coordinated Pb²⁺ ions in perovskite film and mobile Li⁺ ions in HTL, ultimately leading to superior humidity, thermal, light stress, and operational stabilities of PSCs.

Abstract

As the power-conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long-term ambient stability. Here, the application of PCN-224 quantum dots (QDs) is reported, a typical Zr-based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN-224 QDs with abundant Lewis-base groups (e.g., CO, C−N, CN) contribute to high-quality perovskite films with enlarged grain size and reduced defect density by interaction with under-coordinated Pb²⁺. Meanwhile, PCN-224 QDs enable the well-matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN-224 QDs-treated HTL can capture Li⁺ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li-TFSI. Moreover, PCN-224 QDs mitigated Li⁺ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs.

Publication date: January 2023

Source: Nano Energy, Volume 105

Author(s): Hua Zhong, Xudong Liu, Mingxuan Liu, Song Yin, Zhongzhong Jia, Guangsheng Fu, Shaopeng Yang, Weiguang Kong

Herein, a simple and effective oxygen atmosphere low-temperature-processed indium tin oxide (ITO-LT-O₂) cathode buffer layer was developed for fabricating efficient planar perovskite solar cells. The ITO-LT-O₂ cathode buffer layer with an appropriate energy alignment and effective defect suppression that significantly enhanced interfacial charge transfer, resulting in a power conversion efficiency of 21.13%.

Perovskite solar cells (PSCs) have demonstrated high-power conversion efficiency (PCE) and exhibit great application potential in photovoltaic systems. Generally, a typical PSC is accompanied with multiinterfaces; therefore, charge extraction and transport in PSCs are strongly affected by these interfaces. In fact, interfacial energy-level mismatch of carrier transport layer and anode/cathode is also deeply limiting the electrical performance of PSCs. Herein, a low-temperature-processed indium tin oxide (ITO-LT) cathode buffer layer is developed and used for optimizing the energy-level alignment and suppressing defects at the electron transfer layer and cathode interface. It is revealed that a 3 nm ITO-LT cathode buffer layer with an appropriate energy alignment and effective defect suppression could enhance interfacial charge transfer, resulting in a PCE of 21.13% in a planar PSC.

A simple and environmentally friendly method, through boric acid, to remove the residual amine in zinc oxide (ZnO) without decomposing ZnO is reported. Consequently, the optimized tandem organic solar cells (OSCs) output of 19.56% power conversion efficiency and long-term illumination stability of OSCs are significantly improved.

Abstract

Owing to outstanding optoelectronic properties and simple preparation, zinc oxide (ZnO) has widely been used in organic solar cells (OSCs). Although versatile cathode interface materials have been designed in past, ZnO remains indispensable owing to its excellent overall performance. Therefore, solving the persistent problem of residual amine reacting with non-fullerene acceptors will make ZnO superior over other materials, and thus improve the performance and energy budget of OSCs. Herein, a simple, effective, and economical method for removing residual amine in ZnO without distorting ZnO is reported. By accurately comparing the alkalinities of ZnO and residual amine, boric acid (BA) is selected as the amine-removing agent because of its suitable acidic dissociation constant. Moreover, the high water solubility of BA ensures that the post-cleaning process can be easily performed. The work function, electron extraction, and stability of cathode interface layer are optimized through rinsing them with BA. Consequently, the power conversion efficiency (PCE) and stability of OSCs under long-term illumination are significantly improved. The optimal 0.04 and 1.00 cm² single-junction OSCs are based on PBDB-TF:HDO-4Cl:BTP-eC9 bulk heterojunction output 18.40% and 17.42% efficiencies, respectively. Furthermore, tandem OSCs based on the BA-treated ZnO exhibit a 19.56% PCE, demonstrating the reliability of this method.

Synergistic passivation is performed in the direct synthesis of conductive lead sulfide colloidal quantum dot (PbS CQD) inks. The improved passivation effect is intactly delivered to the final photovoltaic device, leading a high open-circuit voltage (V _oc)) of 0.71 V and efficiency of 13.3%, which results in the lowest V _oc loss (0.35 eV) for the reported PbS CQD solar cells.

Abstract

The high open-circuit voltage (V _oc) loss arising from insufficient surface passivation is the main factor that limits the efficiency of current lead sulfide colloidal quantum dots (PbS CQDs) solar cell. Here, synergistic passivation is performed in the direct synthesis of conductive PbS CQD inks by introducing multifunctional ligands to well coordinate the complicated CQDs surface with the thermodynamically optimal configuration. The improved passivation effect is intactly delivered to the final photovoltaic device, leading to an order lower surface trap density and beneficial doping behavior compared to the control sample. The obtained CQD inks show the highest photoluminescence quantum yield (PLQY) of 24% for all photovoltaic PbS CQD inks, which is more than twice the reported average PLQY value of ≈10%. As a result, a high V _oc of 0.71 V and power conversion efficiency (PCE) of 13.3% is achieved, which results in the lowest V _oc loss (0.35 eV) for the reported PbS CQD solar cells with PCE >10%, comparable to that of perovskite solar cells. This work provides valuable insights into the future CQDs passivation strategies and also demonstrates the great potential for the direct-synthesis protocol of PbS CQDs.

A high-performance flexible photodetector is realized by gating an organic electrochemical transistor with a perovskite solar cell, outperforming previously reported flexible photodetectors, which can be attributed to the high transconductance of the transistor. The device can monitor photoplethysmogram signals and peripheral oxygen saturation under ambient light and even remotely. This novel device design demonstrates great potential in emerging wearable optoelectronics.

Abstract

Photodetectors (PDs) are the building block of various imaging and sensing applications. However, commercially available PDs based on crystalline inorganic semiconductors cannot meet the requirements of emerging wearable/implantable applications due to their rigidity and fragility, which creates the need for flexible devices. Here, a high-performance flexible PD is presented by gating an organic electrochemical transistor (OECT) with a perovskite solar cell. Due to the ultrahigh transconductance of the OECT, the device demonstrates a high gain of ≈10⁶, a fast response time of 67 µs and an ultrahigh detectivity of 6.7 × 10¹⁷ Jones to light signals under a low working voltage (≤0.6 V). Thanks to the ultrahigh sensitivity and fast response, the device can track photoplethysmogram signals and peripheral oxygen saturation under ambient light and even provide contactless remote sensing, offering a low-power and convenient way for continuous vital signs monitoring. This work offers a novel strategy for realizing high-performance flexible PDs that are promising for low-power, user-friendly and wearable optoelectronics.

Nature Energy, Published online: 15 November 2022; doi:10.1038/s41560-022-01158-8

Triple-cation (CsMAFA) perovskites are the most widely used absorbers in the perovskite photovoltaic family due to their high performance; however, they suffer from substantial microscale heterogeneity manifested in their photoluminscence emission. Through the careful tuning of a guanidinium iodide surface treatment, these heterogeneous features are largely resolved, thereby boosting the resulting device performance.

Use of the guanidinium iodide (GAI) cation is widely recognized as an interface engineering technique for perovskite solar cells that deliver stability improvements via defect passivation on surfaces and grain boundaries. However, a comprehensive understanding of the relationship between the structural and photophysical properties is lacking. Herein, GAI-induced perovskite structural modifications, including derivative phases and underlying transitions, are detected in GAI surface-treated Cs_0.07MA_0.14FA_0.79Pb(I_0.83Br_0.17)₃ through an analysis of X-ray and electron diffraction and microscopy data. An optimum GAI solution concentration at 10 mg mL⁻¹ can eliminate excess PbI₂, improve crystallinity, and increase grain size of the as-prepared perovskite films. However, a further increase to 20–40 mg mL⁻¹ induces new (FAPbI₃) _x (GA₂PbI₄) _x phases and a reduction in crystallinity and grain size. In addition, from confocal photoluminescence imaging, it is observed that 10 mg mL⁻¹ GAI also helps to remove the microscale spatial heterogeneities, demonstrating optimum device performance. These results show that understanding the impact on structure and microstructure of the selection and concentration of surface treatment agents is critical for the homogenization of perovskite optoelectronic properties and achieving efficient device.

PbI₂-DMSO powders are adopted as a solid additive for isostatic pressing of MAPbI₃ wafers to promote in situ crystal growth. A dense and compact MAPbI₃ wafer exhibits high mobility-lifetime product of 8.70 × 10⁻⁴ cm² V^–1. The X-ray detector shows high sensitivity of 1.58 × 10⁴ µC Gy_air ^–1 cm^–2 and low detection limit of 410 nGy_air s^–1.

Abstract

Although perovskite wafers with a scalable size and thickness are suitable for direct X-ray detection, polycrystalline perovskite wafers have drawbacks such as the high defect density, defective grain boundaries, and low crystallinity. Herein, PbI₂-DMSO powders are introduced into the MAPbI₃ wafer to facilitate crystal growth. The PbI₂ powders absorb a certain amount of DMSO to form the PbI₂-DMSO powders and PbI₂-DMSO is converted back into PbI₂ under heating while releasing DMSO vapor. During isostatic pressing of the MAPbI₃ wafer with the PbI₂-DMSO solid additive, the released DMSO vapor facilitates in situ growth in the MAPbI₃ wafer with enhanced crystallinity and reduced defect density. A dense and compact MAPbI₃ wafer with a high mobility-lifetime (µτ) product of 8.70 × 10⁻⁴ cm² V⁻¹ is produced. The MAPbI₃-based direct X-ray detector fabricated for demonstration shows a high sensitivity of 1.58 × 10⁴ µC Gyair⁻¹ cm⁻² and a low detection limit of 410 nGy_air s⁻¹.

Dimensional management for high-performance perovskite solar modules: An ultrastable imidazolium-based one-dimensional (1D) perovskite structure is developed to passivate the three-dimensional perovskite film toward the stability improvement of module. The 1D layer reduces interface defects and promotes the efficient charge transport. High efficiencies of 24.3% in 0.12 cm²-area device and 19.6% in 36 cm²-total-area module are achieved with excellent operation/damp-heat stabilities.

Abstract

Although the perovskite solar cells have been developed rapidly, the industrialization of perovskite photovoltaics is still facing challenges, especially considering their stability issues. Here, the new type of benzimidazolium salt, N,N′-dialkylbenzimidazolium iodide, is proposed and functionalized to convert the three-dimensional (3D) FACs-perovskite films into one-dimensional (1D) capping layer topped 1D/3D structure either in individual device or module levels. This conformal interface modulation demonstrates that not only can effectively stabilize FACs-based perovskite films by inhibiting the lateral and vertical iodide diffusions in devices or modules, ensuring an excellent operation and environmental stability, but also provides an excellent charge transporting channel through the well-designed 1D crystal structure. Consequently, efficient device performance with power conversion efficiency up to 24.3% is readily achieved. And the large-area perovskite solar modules with high efficiency (19.6% for the active areas of 18 cm²) and long-term stability (about 500 h in AM 1.5G illumination or about 1000 h under double-85 conditions) are also successfully verified.

Tailoring n = 1 pure 2D perovskites on 3D perovskite surface via low-temperature phenethylammonium bromide (PEABr) post-treatment strongly suppresses the defects at the grain boundaries of 3D perovskites, which enables a high open-circuit voltage of 1.284 V and a low open-circuit voltage loss of 0.486 V for highly efficient inverted 1.77-eV wide-bandgap perovskite solar cells.

Abstract

Surface post-treatment using ammonium halides effectively reduces large open-circuit voltage (V _OC) losses in bromine-rich wide-bandgap (WBG) perovskite solar cells (PSCs). However, the underlying mechanism still remains unclear and the device efficiency lags largely behind. Here, a facile strategy of precisely tailoring the phase purity of 2D perovskites on top of 3D WBG perovskite and realizing high device efficiency is reported. The transient absorption spectra, cross-sectional confocal photoluminescence mapping, and cross-sectional Kelvin probe force microscopy are combined to demonstrate optimal defect passivation effect and surface electric-field of pure n = 1 2D perovskites formed atop 3D WBG perovskites via low-temperature annealing. As a result, the inverted champion device with 1.77-eV perovskite absorber achieves a high V _OC of 1.284 V and a power conversion efficiency (PCE) of 17.72%, delivering the smallest V _OC deficit of 0.486 V among WBG PSCs with a bandgap higher than 1.75 eV. This enables one to achieve a four-terminal all-perovskite tandem solar cell with a PCE exceeding 25% by combining with a 1.25-eV low-bandgap PSC.

The PF₆ ⁻ and N-propyl-methyl piperidinium (NPMP⁺) within the CsPbTh₃ perovskite film form Lewis acid–base adducts to effectively passivate iodide vacancy defects, regulate crystal growth, and finally uniformly improve grain quality and decrease the trap density. This combinational strategy enables the CsPbTh₃ perovskite solar cells to achieve high photovoltaic performance and operational stability.

Abstract

All-inorganic cesium-lead-iodide (CsPbI₃Br_{3− x} (2 < x < 3)) perovskite presents preeminent photovoltaic performance and chemical stability. Unfortunately, this kind of material suffers from phase transition to a nonperovskite phase under oxidative chemical stresses. Herein, the introduction of a low concentration of Lewis acid–base adducts (LABAs) is reported to synergistically reduce defect density, optimize interfacial energy alignment, and improve device stability of CsPbI_2.75Br_0.24Cl_0.01 (CsPbTh₃) solar cells. Both theoretical simulations and experimental measurements reveal that the noncoordinating anions, PF₆ ⁻, as a Lewis base can more effectively bind with undercoordinated Pb²⁺ to passivate iodide vacancy defects than the BF₄ ⁻ and absorbed I⁻, and thus the point defects are well suppressed. In addition, N-propyl-methyl piperidinium (NPMP⁺) is selected to assemble with PF₆ ⁻ in CsPbTh₃ film. The NPMP⁺ can regulate the crystal growth and finally homogenize the grain size and decrease the trap density. Consequently, the LABAs strategy can improve the power conversion efficiency of CsPbTh₃ solar cells to 19.02% under 1-sun illumination (100 mW cm⁻²). Fortunately, the NPMP⁺ and PF₆ ⁻-treated CsPbTh₃ film shows great phase stability after storage in ambient air for 250 days, and the power conversion efficiency of corresponding solar cells is almost 76% of the initial value after 60 days aging under ambient conditions.

The atomic optimization is conducted by replacing sulfur in FO-2Cl with selenium, thus affording FOSe-2Cl. A systematical investigation to reveal effects of selenium on energy levels, absorption, charge transfer dynamics and photovoltaic performance performed. Ultimately, the PM6:FOSe-2Cl-based device achieved an improved power conversion efficiency of 15.94% and a reduced energy loss of 0.670 eV.

Abstract

Atomic replacement on platforms of nonfullerene acceptor (NFA) with already excellent performance is expected to further optimize the energy levels, absorptions, and even charge transfer dynamics of NFAs effectively without greatly destroying their superior molecular conformations. On the basis of high-performance F-series NFAs, the structural optimization at atomic level is performed by replacing sulfur atoms in FO-2Cl with selenium atoms, thus affording a new NFA labeled as FOSe-2Cl. FOSe-2Cl not only inherits the good planar configuration of FO-2Cl, but also exhibits more suitable energy levels, redshifted absorption, enhanced molecular packing, and accelerative charge transfer/transport dynamics compared with those of FO-2Cl. With a widely used polymer PM6 as the donor, organic solar cell (OSC) based on FOSe-2Cl affords a significantly improved power conversion efficiency (PCE) of 15.94% with a reduced energy loss (E _loss) of 0.670 eV, with respect to that of FO-2Cl-based OSC with a PCE of 14.94% and E _loss of 0.706 eV. The result represents the best performance reported to date for pyran-fused NFAs and F-series NFAs-based binary OSCs, providing another promising platform to achieve the state-of-the-art OSCs in addition to the well-known Y-series NFAs.

Two benzotriazole-based polymer acceptors, PTz-BO and PTz-C11, featuring the same molecular backbone and different side chain are synthesized. Compared to PTz-C11, PTz-BO shows slightly blueshifted absorption and a higher lowest unoccupied molecular orbitals energy level. The ternary all-polymer solar cells (all-PSCs) based on a combination of PTz-C11 and PTz-BO yield a high efficiency of 16.58%, representing the highest efficiency reported for benzotriazole-based all-PSCs thus far.

Abstract

The power conversion efficiencies (PCEs) of all-polymer solar cells (all-PSCs) have already exceeded 17%. However, the limited absorption range of an all-polymer system results in significantly reduced short-circuit current density (J _sc), which eventually influences the PCE improvement. To broaden the light absorption of polymer acceptors, herein, benzotriazole is introduced in the core unit of small molecule acceptors and thus two narrow-bandgap polymer acceptors named PTz-BO and PTz-C11 featuring the same molecular backbone and different side-chain length are synthesized. Compared with PTz-C11, the PTz-BO based-all PSCs deliver a slightly reduced J _sc, a large open-circuit voltage (V _oc) and a low voltage loss below 0.50 V. Moreover, ternary all-PSCs are constructed by introducing PTz-C11 as a guest component. Benefiting from the reduced recombination, improved exciton generation and dissociation, and balanced charge transport, a high efficiency of 16.58% is obtained for the ternary all-PSCs, with a high J _sc over 25 mA cm⁻² without sacrificing the V _oc. Such result represents the highest efficiency reported for benzotriazole-based all-PSCs in the literature thus far. This work demonstrates the great potential of benzotriazole for the synthesis of efficient narrow-bandgap polymer acceptors.

A novel multifunctional polymer, poly(methyl methacrylate-co-acrylamide), was designed and utilized to synergistically passivate the under-coordinated Pb²⁺ and anchor the I^- of the [PbI₆]⁴⁻ octahedron on the surface of a perovskite film. This passivation leads to an enhancement in the open-circuit voltage from 1.12 to 1.22 V and improved stability in solar cell devices, with the device maintaining 95 % of the initial power conversion efficiency (PCE) over 1000 h of maximum power point tracking. Additionally, a large-area solar cell device was fabricated using this approach, achieving a PCE of 20.64 %.

Abstract

Metal-cation defects and halogen-anion defects in perovskite films are critical to the efficiency and stability of perovskite solar cells (PSCs). In this work, a random polymer, poly(methyl methacrylate-co-acrylamide) (PMMA-AM), was synthesized to serve as an interfacial passivation layer for synergistically passivating the under-coordinated Pb²⁺ and anchor the I^- of the [PbI₆]⁴⁻ octahedron. Additionally, the interfacial PMMA-AM passivation layer cannot be destroyed during the hole transport layer deposition because of its low solubility in chlorobenzene. This passivation leads to an enhancement in the open-circuit voltage from 1.12 to 1.22 V and improved stability in solar cell devices, with the device maintaining 95 % of the initial power conversion efficiency (PCE) over 1000 h of maximum power point tracking. Additionally, a large-area solar cell module was fabricated using this approach, achieving a PCE of 20.64 %.

A thin film of ionic salt (NaBH₄) is deposited at the PEDOT:PSS/MAPbI_3−x Cl _x interface, simultaneously achieving interfacial modification and crystallization control. The electrostatic coupling between NaBH₄ and PEDOT:PSS/perovskite results in better energy level alignment and reduced interfacial defects. A satisfactory power conversion efficiency (PCE) of 20.21% is obtained, and the long-term stability of the device is over 1000 h.

Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) is widely used as a hole transport layer in inverted perovskite solar cells (PSCs). However, due to the serious interface defects, imperfect energy level arrangement, and low hole transfer rate between PEDOT:PSS and perovskite, the realization of efficient and stable inverted PSCs is hindered. Herein, ionic salt sodium borohydride is used as an interfacial modifier between PEDOT:PSS and MAPbI_3−x Cl _x . NaBH₄ acts as an anchor to bond Pb²⁺ to the PEDOT:PSS surface and guides the growth of the perovskite. The champion power conversion efficiency (PCE) of the device based on NaBH₄-PEDOT:PSS reaches 20.21%, which is improved by 27.5% compared with the device based on PEDOT:PSS (15.84%). This PCE is one of the highest in inverted PSCs with PEDOT:PSS as the hole transport layer and MAPbI_3−x Cl _x as the active layer. The improved device performance is mainly attributed to the reduced valence band edge of PEDOT:PSS which matches better with the HOMO of MAPbI_3−x Cl _x , and the hole transfer rate is increased from 2.65 × 10¹⁰ to 3.69 × 10¹⁰ s⁻¹. The long-term stability of the optimized device exceeds 1000 h. This work provides a simple and effective strategy to improve the PCE and stability of inverted PSCs, which is a benefit for future popularization.

Metal halide perovskites have emerged as well-suited materials for photovoltaic and optoelectronic applications. A drawback is their photo-structural–chemical instability under normal operating conditions. Herein, in situ X-ray diffraction and X-ray excited optical luminescence, applying either X-ray or sunlight stimuli under a controlled atmosphere, correlating structural and optical responses of thin films of the compounds are employed.

Metal halide perovskites are versatile materials for photovoltaic and optoelectronic applications owing to their adjustable bandgap and emission properties. Nevertheless, a drawback is their photo-structural–chemical instability. Herein, structural and optical responses of metal halide perovskite films, exploiting in situ X-ray and visible light stimuli under dry and humid atmospheres, are correlated. It shows that the interplay of the physical parameters responsible for sample evolution depends in a nontrivial way on the nature of the excitation, radiation power density, and moisture conditions. Two perovskite samples demonstrate the relevance of each composition. They are resilient under a dry atmosphere, but the presence of water or oxygen molecules in the ambient air leads to structural and optical changes under irradiation. However, the sample reaction depends on the photons’ excitation energy and power density to be effective. Under a dry atmosphere, the halide segregation involving Br and I atoms does not occur for the low-power density of X-ray and sunlight excitations. On the contrary, under the ambient air atmosphere, compound stability depends on sample composition, which relates to defects and traps, and the excitation source. Herein, the probe's relevance to perovskites’ photoinduced structural and optical responses is highlighted.

A strategy to modulate the crystal nucleation and passivate defects in scalable-coated perovskite films via natural amino acid is presented. The flexible perovskite solar modules with the addition of amino acid are fabricated, achieving excellent efficiencies of 12.1% and 11.2% with aperture areas of 185 and 333 cm², respectively.

Abstract

Upscaling large-area formamidinium (FA)-based perovskite solar cells (PSCs) has been considered as one of the most promising routes for the commercial applications of this rising photovoltaics technology. Here, a natural amino acid, phenylalanine (Phe), is introduced to regulate the nucleation and crystal growth process of the large-scale coating of FA-based perovskite films. Better film coverage and larger grain sizes are observed after adding Phe. Moreover, it is found that Phe can effectively passivate defects within perovskite films and suppress the nonradiative recombination due to the strong interaction with under-coordinated Pb²⁺ ions in the perovskite films. Rigid PSCs based on the blade-coated perovskite films containing Phe obtain a champion efficiency of 21.95%. The corresponding unencapsulated devices also exhibit excellent ambient stability, retaining 95% of their initial efficiencies after storage in the glovebox at 20 °C for 1000 h. Further, the strategy is applied to fabricate flexible PSCs and modules on polyethylene terephthalate/indium doped tin oxide substrates via slot-die coating. Phe modified flexible devices achieve outstanding efficiencies of 20.21%, 12.1%, and 11.2% with aperture areas of 0.10, 185, and 333 cm², respectively. The strategy here has paved a promising way for the large-scale production of flexible PSCs.

An oxime acid-based additive (EHA) is adopted as a multidentate-coordinate agent in perovskite solar cells. Benefitting from the crystallization modulation and defect passivation effect, a simultaneous enhancement in photovoltaic performance and device stability is attained in the EHA-modified perovskite solar cells.

Abstract

Crystal growth regulation has become an effective solution to reduce the defects at grain boundaries (GBs) and surfaces of perovskite films for better photovoltaic performances. Oxime acid materials are maturely used as selective collectors in the flotation separation of oxide minerals. Such materials, showing a strong coordination effect and high selectivity with lead, may have great potential in controlling the crystal growth and passivating the defect of perovskite film, which are rarely applied in perovskite solar cells (PerSCs). Herein, an oxime acid-based material with multi-coordination sites, ethyl 2-(2-aminothiazole-4-yl)-2-hydroxyiminoacetate (EHA), is incorporated into the PbI₂ precursor solution to fabricate high-performance PerSCs using a two-step method. The multidentate coordination effect of EHA can link and integrate the PbI₂ colloidal clusters to achieve pre-aggregation in the PbI₂ precursor solution, facilitating the sequent crystal growth progress of perovskite film. Meanwhile, EHA can connect grains and fill GBs, which is favorable for charge transfer and passivating both Pb-I anti-site and iodine vacancy defects. As a result, the optimal devices show an enhanced efficiency of 24.1% and excellent humidity and thermal stability. This work affords a promising strategy to fabricate efficient and stable PerSCs via multidentate coordination-induced crystallization control and GB passivation.

A facile surface reconfiguration methodology (SRM) is reported for the first time as a general approach to tune the coupling between hybrid FAPbI₃ perovskite QDs, which is exploited for improved charge transport for fabricating high-quality QD arrays and PV devices, leading to a record-high efficiency approaching 15 % for FAPbI₃ perovskite QD solar cell.

Abstract

For emerging perovskite quantum dots (QDs), understanding the surface features and their impact on the materials and devices is becoming increasingly urgent. In this family, hybrid FAPbI₃ QDs (FA: formamidium) exhibit higher ambient stability, near-infrared absorption and sufficient carrier lifetime. However, hybrid QDs suffer from difficulty in modulating surface ligand, which is essential for constructing conductive QD arrays for photovoltaics. Herein, assisted by an ionic liquid formamidine thiocyanate, we report a facile surface reconfiguration methodology to modulate surface and manipulate electronic coupling of FAPbI₃ QDs, which is exploited to enhance charge transport for fabricating high-quality QD arrays and photovoltaic devices. Finally, a record-high efficiency approaching 15 % is achieved for FAPbI₃ QD solar cells, and they retain over 80 % of the initial efficiency after aging in ambient environment (20–30 % humidity, 25 °C) for over 600 h.