JIALINGBO

Nature Energy, Published online: 17 April 2023; doi:10.1038/s41560-023-01249-0

The researchers developed a novel in situ passivation of SnO₂ with optimized SnO₂/perovskite interfacial carrier extraction and transport for efficient and stable perovskite solar cells (PSCs). A champion power conversion efficiency (PCE) of 24.91 % and a champion fill factor (FF) up to 0.852 were obtained.

Abstract

Perovskite solar cells (PSCs) based on SnO₂ electron transport layers have attracted extensive research due to their compelling photovoltaic performance. Herein, we presented an in situ passivation of SnO₂ with low-cost hydroxyacid potassium synergist during deposition to optimize the interface carrier extraction and transport for high power conversion efficiency (PCE) and stabilities of PSCs. The orbital overlap of the carboxyl oxygen with the Sn atom alongwith the homogenous nano-particle deposition effectively suppresses the interfacial defects and releases the internal residual strains in the perovskite. Accordingly, a PCE of 24.91 % with a fill factor (FF) up to 0.852 is obtained for in situ passivated devices, which is one of the highest values for SnO₂-based PSCs. Moreover, the unencapsulated device maintained 80 % of its initial PCE at 80 °C over 600 h, 100 % PCE at ambient conditions for 1300 h, and 98 % after one week maximum power point tracking (MPPT) under continuous AM1.5G illumination.

Alkyl-chain length in amine tethered fullerenes has a large effect on electron transport layer (ETL) passivation in perovskite solar cells, with longer chains improving charge collection, power conversion efficiency (PCE), and stability. The amine binds to the underlying tin oxide and templates perovskite crystallization.

Abstract

Efficient surface passivation of perovskite solar cells (PSC) using treatment with ammonium salts is demonstrated as an efficient method to enhance the device performance, owing to the affinity between the amine group and [PbI₆]⁴⁻ octahedron. However, due to their high solubility in polar solvents (DMF/DMSO), ammonium salts are more difficult to use in passivation of the interface between the electron transport layer and perovskite thin film in n-i-p structured PSCs. In this report, this work successfully links the amine group with a fullerene through a series of increasing carbon chain length, from two to twelve methylene units (FC-X, X = 2, 6, 12), and then introduce the synthesized molecules as interface passivation layers into SnO₂-based planar n-i-p PSCs. Results show that the interface passivation effect is highly dependent on the side-chain length, and the longer chain length amine-functionalized fullerene is more beneficial for the device performance. A power conversion efficiency as high as 21.2% is achieved by using FC-12. The surface energy, perovskite crystallite size and electron transfer capacity correlate with the linker chain length. This work develops an amine-induced anchored crystallization of perovskite to unravel the mechanism of this passivation effect. As expected, enhanced device stability is also observed in the FC-12 passivated PSCs.

Publication date: June 2023

Source: Nano Today, Volume 50

Author(s): Dan Wang, Xihong Guo, Guikai Zhang, Yunpeng Liu, Shuhu Liu, Zhongying Zhang, Yuru Chai, Yu Chen, Jing Zhang, Baoyun Sun

A new understanding and architecture enabling efficient and stable perovskite solar cells built on metal substrates is presented. The efficiency and fill-factor losses due to area upscaling are remarkably reduced by one order of magnitude relative to the counterparts on conventional transparent conductive oxide (TCO) glass, highlighting an alternative pathway for upscaling and module design.

Abstract

Conventional perovskite solar cells (PSC) built on transparent conductive oxide (TCO) glass face a fundamental challenge to retain fill factor (FF) for large-area upscaling due to series resistance loss. Building a perovskite solar cell on metal has the potential to reduce this FF loss and is promising for flexible applications. However, their efficiency and stability lag far behind their TCO counterparts. Herein, findings on the complex chemical reactions and degradation-promoting processes at different perovskite/metal (Cu, Au, Ag, and Mo) interfaces, which are closely linked with the inherent stability; and the interlayer engineering for perovskite/metal interface's band alignment, which plays an essential role in achieving high efficiency, are reported. Leveraging these findings, 21% power conversion efficiency (PCE) is achieved for 1 cm² perovskite solar cells using a p–i–n top-illumination structure on a molybdenum substrate, the highest reported for a PSC built on metal. Notably, the FF and PCE losses due to area upscaling are remarkably reduced by one order of magnitude relative to the counterparts on conventional TCO glass, highlighting an alternative pathway for PSC upscaling and module design.

A simple, facile, and versatile strategy of pre-grafted halides is developed for strengthening the SnO₂–perovskite buried interface, in which precise manipulation of perovskite defects and carrier dynamics has been realized by altering halide electronegativity (χ).

Abstract

The perovskite buried interfaces have demonstrated pivotal roles in determining both the efficiency and stability of perovskite solar cells (PSCs); however, challenges remain in understanding and managing the interfaces due to their non-exposed feature. Here, we proposed a versatile strategy of pre-grafted halides to strengthen the SnO₂–perovskite buried interface by precisely manipulating perovskite defects and carrier dynamics through alteration of halide electronegativity (χ), thereby resulting in both favorable perovskite crystallization and minimized interfacial carrier losses. Specifically, the implementation of fluoride with the highest χ induces the strongest binding affinity to uncoordinated SnO₂ defects and perovskite cations, leading to retarded perovskite crystallization and high-quality perovskite films with reduced residual stress. These improved properties enable champion efficiencies of 24.2% (the control: 20.5%) and 22.1% (the control: 18.7%) in rigid and flexible devices with extremely low voltage deficit down to 386 mV, all of which are among the highest reported values for PSCs with a similar device architecture. In addition, the resulting devices exhibit marked improvements in the device longevity under various stressors of humidity (>5000 h), light (1000 h), heat (180 h), and bending test (10 000 times). This method provides an effective way to improve the quality of buried interfaces toward high-performance PSCs.

Antisolvent engineering is proposed to realize high-quality dominantly oriented perovskite film by the antisolvent of isopropyl alcohol (IPA). The interaction between IPA and PbI₂ leads to the direct crystallization of (111)-α-FAPbI₃ at room temperature, sidestepping the intermediates of PbI₂•DMSO, FA₂Pb₃I₈•4DMSO, and δ-FAPbI₃. Solar cells based on (111)-α-FAPbI₃ demonstrate improved performance compared to the randomly oriented perovskite films treated by other antisolvents.

Abstract

Fabricating perovskite films with a dominant crystal orientation is an effective path to realizing quasi-single-crystal perovskite film, which can eliminate the fluctuation of the electrical properties in films arising from grain-to-grain variations, and improve the performance of perovskite solar cells (PSCs). Perovskite (FAPbI₃) films based on one-step antisolvent methods usually suffer from chaotic orientations due to the inevitable intermediate phase conversion from intermediates of PbI₂•DMSO, FA₂Pb₃I₈•4DMSO, and δ-FAPbI₃ to α-FAPbI₃. Here, a high-quality perovskite film with (111) preferred orientation ((111)-α-FAPbI₃) using a short-chain isomeric alcohol antisolvent, isopropanol (IPA) or isobutanol (IBA), is reported. The interaction between IPA and PbI₂ leads to a corner-sharing structure instead of an edge-sharing PbI₂ octahedron, sidestepping the formation of these intermediates. With the volatilization of IPA, FA⁺ can replace IPA in situ to form α-FAPbI₃ along the (111) direction. Compared to randomly orientated perovskites, the dominantly (111) orientated perovskite ((111)-perovskite) exhibits improved carrier mobility, uniform surface potential, suppressed film defects and enhanced photostability. PSCs based on the (111)-perovskite films show 22% power conversion efficiency and excellent stability, which remains unchanged after 600 h continuous working at maximum power point, and 95% after 2000 h of storage in atmosphere environment.

A BF₄ ⁻ anion–assisted molecular doping (AMD) strategy is proposed to enhance the doping level of both poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] and poly[N,N′-bis(4-butilphenyl)-N,N′-bis(phenyl)-benzidine] films and induce the formation of p–n homojunctions in the perovskite film, which results in a highest power conversion efficiency of 24.26% due to the reduced energy loss at the buried interface.

Abstract

The energy loss (E _loss) aroused by inefficient charge transfer and large energy level offset at the buried interface of p-i-n perovskite solar cells (PVSCs) limits their development. In this work, a BF₄ ⁻ anion-assisted molecular doping (AMD) strategy is first proposed to improve the charge transfer capability of hole transport layers (HTLs) and reduce the energy level offset at the buried interface of PVSCs. The AMD strategy improves the carrier mobility and density of poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and poly[N,N′-bis(4-butilphenyl)-N,N′-bis(phenyl)-benzidine] (Poly-TPD) HTLs while lowering their Fermi levels. Meanwhile, BF4− anions regulate the crystallization and reduce donor-type iodine vacancies, resulting in the energetics transformation from n-type to p-type on the bottom surface of perovskite film. The faster charge transfer and formed p–n homojunction reduce charge recombination and E _loss at the HTL/perovskite buried interface. The PVSCs utilizing AMD treated PTAA and Poly-TPD as HTLs demonstrate a highest power conversion efficiency (PCE) of 24.26% and 22.65%, along with retaining 90.97% and 85.95% of the initial PCE after maximum power point tracking for 400 h. This work provides an effective way to minimize the E _loss at the buried interface of p-i-n PVSCs by accelerating charge transfer and forming p–n homojunctions.

An effective interfacial defect and carrier management strategy is developed by synergistically modulating organic functional groups and spatial conformation of organic ammonium salt modification molecules. The 3-ammonium propionic acid iodide-modified device based on vacuum flash technology achieves an alluring peak efficiency of 24.72% (certified 23.68%), which is among highly efficient devices fabricated without antisolvents.

Abstract

Interfacial nonradiative recombination loss is a huge barrier to advance the photovoltaic performance. Here, one effective interfacial defect and carrier dynamics management strategy by synergistic modulation of functional groups and spatial conformation of ammonium salt molecules is proposed. The surface treatment with 3-ammonium propionic acid iodide (3-APAI) does not form 2D perovskite passivation layer while the propylammonium ions and 5-aminopentanoic acid hydroiodide post-treatment lead to the formation of 2D perovskite passivation layers. Due to appropriate alkyl chain length, theoretical and experimental results manifest that COOH and NH₃ ⁺ groups in 3-APAI molecules can form coordination bonding with undercoordinated Pb²⁺ and ionic bonding and hydrogen bonding with octahedron PbI₆ ⁴⁻, respectively, which makes both groups be simultaneously firmly anchored on the surface of perovskite films. This will strengthen defect passivation effect and improve interfacial carrier transport and transfer. The synergistic effect of functional groups and spatial conformation confers 3-APAI better defect passivation effect than 2D perovskite layers. The 3-APAI-modified device based on vacuum flash technology achieves an alluring peak efficiency of 24.72% (certified 23.68%), which is among highly efficient devices fabricated without antisolvents. Furthermore, the encapsulated 3-APAI-modified device degrades by less than 4% after 1400 h of continuous one sun illumination.

By the passivation of 12-aminolauric acid, the efficiency of the perovskite solar cells (PSCs) can increase from 18.42% to 19.96%. The treatments of the passivation agents also increase the hydrophobicity of the perovskite films, improving the stability of the PSCs.

Defects in perovskite film are sources of charge recombination centers, which are detrimental to the performance of perovskite solar cells (PSCs). To decrease the density of defects, dodecylamine (DAM), dodecylic acid (DAC), and 12-aminolauric acid (ALA) are utilized as additives to prepare methyl ammonium lead iodide (MAPbI₃) perovskite films. Herein, the passivation effects of these molecules on the properties of the MAPbI₃ films and the performances of the corresponding PSCs are studied. The results show that DAM and DAC which contain –NH₂ and –COOH groups, respectively, can increase the PCEs of the devices. This result implies that both groups serve as the Lewis base, passivating the defects of undercoordinated Pb²⁺. For the ALA molecules, the –NH₂ and –COOH groups are present simultaneously at the two ends of the molecule; the passivation ability is more significant than the others, which is attributable to the synergistic effects of the two groups. By the passivation of ALA, the PCE of the PSC can increase from 18.42% to 19.96% under one sun illumination. Furthermore, the treatments of the passivation agents also increase the hydrophobicity of the perovskite films, improving the stability of the PSCs.

Publication date: 15 June 2023

Source: Nano Energy, Volume 111

Author(s): Daquan Zhang, Yudong Zhu, Rui Jiao, Jinming Zhou, Qianpeng Zhang, Swapnadeep Poddar, Beitao Ren, Xiao Qiu, Bryan Cao, Yu Zhou, Chen Wang, Ke-Fan Wang, Yunlong Zi, Haibo Zeng, Mitch Guijun Li, Hongyu Yu, Qingfeng Zhou, Zhiyong Fan

A fully wrapped structure is proposed to passivate the surface of the free-standing CsPbBr₃ single-crystal films in light-emitting diode device, which can achieve high color purity (FWHM = 15.8 nm) and realize a large luminescent area (>2 mm²). This study represents remarkable advancement in single-crystal perovskite materials and feasibility of free-standing film-based device.

Abstract

High color purity is one of the important features for single-crystal metal halide perovskite light-emitting diode (LED). Despite single-crystal perovskite showing low bulk defect concentration, single-crystal perovskite LEDs do not exhibit high color purity advantage due to the absence of effective surface defect passivation. Herein, one fully wrapped structure is proposed to passivate the surface of the free-standing CsPbBr₃ single-crystal films. The surface of CsPbBr₃ single-crystal films is wrapped by ultra-thin polymethyl methacrylate, precisely controlling the thickness. The single-crystal perovskite film device can achieve high color purity with a full width at half maximum (FWHM) of 15.8 nm) and a large luminescent area of 2.25 mm². It is observed that surface passivation is due to interaction of CO bond in polymer chains with the Lewis acid PbBr₂. The passivated perovskite single-crystal films significantly improve carrier lifetime and suppress surface defects. It is noteworthy that the passivated free-standing single-crystal perovskite films are feasible to build up a vertical LED device structure, avoiding the edge glowing and short-circuiting of the LED device. This study demonstrates the large luminescent area of the high-quality millimetre-scale free-standing single-crystal films for wide color gamut display and vertical optoelectronic devices.

An additive-assisted two-step annealing process was developed for high-performance CsSnI₃ perovskite solar cells (PSCs). The carbazide (CBZ) can slow down crystallization for dense coverage at 80 °C. After further annealing at 150 °C, the uncoordinated CBZ reduces Sn⁴⁺ to Sn²⁺ with few deep traps. The efficiency of CsSnI₃:CBZ is 11.21%, which is the highest performance for CsSnI₃-based PSCs to date.

Abstract

Inorganic CsSnI₃ with low toxicity and a narrow bandgap is a promising photovoltaic material. However, the performance of CsSnI₃ perovskite solar cells (PSCs) is much lower than that of Pb-based and hybrid Sn-based (e.g., CsPbX₃ and CH(NH₂)₂SnX₃) PSCs, which may be attributed to its poor film-forming property and the deep traps induced by Sn⁴⁺. Here, a bifunctional additive carbazide (CBZ) is adapted to deposit a pinhole-free film and remove the deep traps via two-step annealing. The lone electrons of the NH₂ and CO units in CBZ can coordinate with Sn²⁺ to form a dense film with large grains during the phase transition at 80 °C. The decomposition of CBZ can reduce Sn⁴⁺ to Sn²⁺ during annealing at 150 °C to remove the deep traps. Compared with the control device (4.12%), the maximum efficiency of the CsSnI₃:CBZ PSC reaches 11.21%, which is the highest efficiency of CsSnI₃ PSC reported to date. A certified efficiency of 10.90% is obtained by an independent photovoltaic testing laboratory. In addition, the unsealed CsSnI₃:CBZ devices maintain initial efficiencies of ≈100%, 90%, and 80% under an inert atmosphere (60 days), standard maximum power point tracking (650 h at 65 °C), and ambient air (100 h), respectively.

Nature, Published online: 29 March 2023; doi:10.1038/s41586-023-05992-y

A novel nickel oxide hole transport layer top-down synthesis route via electrochemical anodization is developed. A-NiO shows outstanding optoelectrical properties such as uniform film thickness, enhanced transmittance, low trap density, and high hole extraction ability. The A-NiO-based inverted perovskite solar cell shows improved power conversion efficiency of 21.9% and long-term stability.

The hole transport layer (HTL) plays a key role in inverted perovskite solar cells (PSCs), and nickel oxide has been widely adopted for HTL. However, a conventional solution-processed bottom-up approach for NiO _x (S-NiO) HTL fabrication shows several drawbacks, such as poor coverage, irregular film thickness, numerous defect sites, and inefficient hole extraction from the perovskite layer. To address these issues, herein, a novel NiO _x HTL top-down synthesis route via electrochemical anodization is developed. The basicity of the electrolyte used in anodization considerably influences electrochemical reactions and results in the structure of the anodized NiO _x (A-NiO). The optimized A-NiO provides outstanding optoelectrical properties, including uniform film thickness, enhanced transmittance, deep-lying valance band, low trap density, and better hole extraction ability from the perovskite. Owing to these advantages, the A-NiO-based inverted PSC exhibits an improved power conversion efficiency of 21.9% compared with 19.1% for the S-NiO-based device. In addition, the A-NiO device shows a higher inlet and long-term ambient stability than the S-NiO device due to the superior hole transfer ability of A-NiO, which suppresses charge accumulation between NiO _x and the perovskite interface.

Herein, the role of ionic liquids in perovskite solar cells as additives, solvents, interface engineering, and charge transport layer is discussed. This review guides the researchers in understanding bulk doping and interface engineering for fabricating efficient, stable, and eco-friendly perovskite solar cells.

Although the power conversion efficiency of perovskite solar cells (PSCs) has reached 25.7%, there is still great potential for improvement in their performance and stability. In the past few years, ionic liquids (ILs) have been extensively investigated and demonstrated to enhance the efficiency and stability of devices substantially. Herein, the role of ILs in PSCs as additives, solvents, interface engineering, and charge transport layer is reviewed. Also, this review will guide the researchers in understanding bulk doping and interface engineering for efficient and stable PSCs.

A unique intermediate phase engineering strategy is developed to overcome the incomplete and random transformation of PbI₂ film with organic ammonium salts by simultaneously introducing 2,2-azodi(2-methylbutyronitrile) to both PbI₂ precursor solution and organic ammonium salts. This helps to achieve perovskite solar cells with efficiency >25% and good stability of remaining 96% initial efficiency in the maximum power point tracking measurement after 1000 h.

Abstract

Sequential deposition has been widely employed to modulate the crystallization of perovskite solar cells because it can avoid the formation of nucleation centers and even initial crystallization in the precursor solution. However, challenges remain in overcoming the incomplete and random transformation of PbI₂ films with organic ammonium salts. Herein, a unique intermediate phase engineering strategy has been developed by simultaneously introducing 2,2-azodi(2-methylbutyronitrile) (AMBN) to both PbI₂ and ammonium salt solutions to regulate perovskite crystallization. AMBN not only coordinates with PbI₂ to form a favorably mesoporous PbI₂ film due to the coordination between Pb²⁺ and the cyano group (C≡N), but also suppresses the vigorous activity of FA⁺ ions by interacting with FAI, leading to the full PbI₂ transformation with the preferred orientation. Therefore, perovskites with favorable facet orientations are obtained, and the defects are largely suppressed owing to the passivation of uncoordinated Pb²⁺ and FA⁺. As a result, a champion power conversion efficiency over 25% with a stabilized efficiency of 24.8% is achieved. Moreover, the device exhibits an improved operational stability, retaining 96% of initial power conversion efficiency under 1000 h continuous white-light illumination with an intensity of 100 mW cm⁻² at ≈55 °C in N₂ atmosphere.

The researchers introduce a multifunctional potassium 4-chlorophenyltrifluoroborate salt as additives for perovskite precursor to improve the performance perovskite solar cells by passivating defects, promoting crystallization process of the perovskite film and suppressing non-radiative recombination in the film. The optimal devices show an enhanced efficiency of 24.50% with remarkable thermal and long-term stability.

Abstract

Despite the rapid developments are achieved for perovskite solar cells (PSCs), the existence of various defects in the devices still limits the further enhancement of the power conversion efficiency (PCE) and the long-term stability of devices. Herein, the efficient organic potassium salt (OPS) of para-halogenated phenyl trifluoroborates is presented as the precursor additives to improve the performance of PSCs. Studies have shown that the 4-chlorophenyltrifluoroborate potassium salt (4-ClPTFBK) exhibits the most effective interaction with the perovskite lattice. Strong coordination between BF₃ ⁻/halogen in anion and uncoordinated Pb²⁺/halide vacancies, along with the hydrogen bond between F in BF₃ ⁻ and H in FA⁺ are observed. Thus, due to the synergistic contribution of the potassium and anionic groups, the high-quality perovskite film with large grain size and low defect density is achieved. As a result, the optimal devices show an enhanced efficiency of 24.50%, much higher than that of the control device (22.63%). Furthermore, the unencapsulated devices present remarkable thermal and long-term stability, maintaining 86% of the initial PCE after thermal test at 80 °C for 1000 h and 95% after storage in the air for 2460 h.

With tailored conjugated ligand design, the 2D/3D heterostructure built in perovskite solar cells enhances the interface adhesion between the polymeric hole-transporting layer—PTAA and perovskite, and at the same time, realizes a uniform growth of 2D structure on top of 3D perovskite. Therefore, the as-fabricated device yields a 23.7% power conversion efficiency, along with excellent stability.

Abstract

Perovskite solar cells (PSCs) have delivered a power conversion efficiency (PCE) of more than 25% and incorporating polymers as hole-transporting layers (HTLs) can further enhance the stability of devices toward the goal of commercialization. Among the various polymeric hole-transporting materials, poly(triaryl amine) (PTAA) is one of the promising HTL candidates with good stability; however, the hydrophobicity of PTAA causes problematic interfacial contact with the perovskite, limiting the device performance. Using molecular side-chain engineering, a uniform 2D perovskite interlayer with conjugated ligands, between 3D perovskites and PTAA is successfully constructed. Further, employing conjugated ligands as cohesive elements, perovskite/PTAA interfacial adhesion is significantly improved. As a result, the thin and lateral extended 2D/3D heterostructure enables as-fabricated PTAA-based PSCs to achieve a PCE of 23.7%, improved from the 18% of reference devices. Owing to the increased ion-migration energy barrier and conformal 2D coating, unencapsulated devices with the new ligands exhibit both superior thermal stability under 60 °C heating and moisture stability in ambient conditions.

The introduction of 3-AzTca regulates the mineralization of PbI₂ and perovskite by strengthening the metallic Pb frame, thereby reducing the defects and improving the environmental stability of PbI₂ and perovskite film. The champion perovskite solar cell achieves a low voltage deficit of 0.37 V, an efficiency of 22.79%, and enhanced stability.

Abstract

Both the uncoordinated Pb²⁺ and excess PbI₂ in perovskite film will create defects and perturb carrier collection, thus leading to the open-circuit voltage (V _OC) loss and inducing rapid performance degradation of perovskite solar cells (PSCs). Herein, an additive of 3-aminothiophene-2-carboxamide (3-AzTca) that contains amide and amino and features a large molecular size is introduced to improve the quality of perovskite film. The interplay of size effect and adequate bonding strength between 3-AzTca and uncoordinated Pb²⁺ regulates the mineralization of PbI₂ and generates low-dimensional PbI₂ phase, thereby boosting the crystallization of perovskite. The decreased defect states result in suppressed nonradiative recombination and reduced V _OC loss. The power conversion efficiency (PCE) of modified PSC is improved to 22.79% with a high V _OC of 1.22 V. Moreover, the decomposition of PbI₂ and perovskite films is also retarded, yielding enhanced device stability. This study provides an effective method to minimize the concentration of uncoordinated Pb²⁺ and improve the PCE and stability of PSCs.

Potassium 1,1,2,2,3,3-hexafluoroprop-ane-1,3-disulfonimide (KHFDF) is introduced into PbI₂ precursor solution to passivate various defects and improve the crystalline quality of perovskite films. Assisted by Lewis coordination, hydrogen bonding, and ionic interaction between KHFDF and perovskite, better crystal orientation and reduced trap-state density perovskite crystallites are achieved, yielding a power conversion efficiency of 24.15% and long-term humidity stability and thermostability.

Abstract

Organic-inorganic lead halide perovskite are promising photovoltaic materials, but their intrinsic defects and crystalline quality severely deteriorate the solar cells efficiency and stability. Herein, potassium 1,1,2,2,3,3-hexafluoroprop-ane-1,3-disulfonimide (KHFDF) is introduced into PbI₂ precursor solution to passivate various defects and improve the crystalline quality of perovskite films. It is found that KHFDF can inhibit PbI₂ crystallization, thus tuning the crystal orientation and growth of perovskite films. Furthermore, KHFDF with dual-functional sulfonyl group cannot only passivate grain boundaries (GBs), but also passivate the defects at GBs via strong interaction with undercoordinated Pb²⁺ and/or hydrogen bonding with FA⁺, while the K⁺ counter cations allow ionic interaction with undercoordinated I⁻. As a result, the KHFDF-modified films exhibit high quality with a larger grain size and a reduced trap-state density, thereby suppressing the trap-state nonradiative recombination. And the devices show a champion efficiency up to 24.15%, benefiting from a sharp enhancement of open-circuit voltage (V _oc) of 1.183 V and fill factor of 81.78%. In addition, due to the enhanced humidity tolerance and chemical structure stability, the devices exhibit excellent long-term humidity and thermal stability without encapsulation.

High-quality Sn–Pb perovskites and excellent contacts at the perovskite/C₆₀ interface are developed by introducing a one-in-all modifier. The introduction of cysteine hydrochloride (CysHCl) to Sn–Pb perovskites restrains non-radiative recombination and facilitates electron transfer. Consequently, the CysHCl-processed devices achieve the highest power conversion efficiency (PCE) of 22.15% for low-bandgap (LBG) Sn–Pb perovskite solar cell (PSC) and 26.16% for all-perovskite monolithic tandem devices.

Abstract

All-perovskite tandem solar cells (TSCs) hold great promise in terms of ultrahigh efficiency, low manufacturing cost, and flexibility, stepping forward to the next-generation photovoltaics. However, their further development is hampered by the relatively low performance of low-bandgap (LBG) tin (Sn)–lead (Pb) perovskite solar cells (PSCs). Improving the carrier management, including suppressing trap-assisted non-radiative recombination and promoting carrier transfer, is of great significance to enhance the performance of Sn–Pb PSCs. Herein, a carrier management strategy is reported for using cysteine hydrochloride (CysHCl) simultaneously as a bulky passivator and a surface anchoring agent for Sn–Pb perovskite. CysHCl processing effectively reduces trap density and suppresses non-radiative recombination, enabling the growth of high-quality Sn–Pb perovskite with greatly improved carrier diffusion length of >8 µm. Furthermore, the electron transfer at the perovskite/C₆₀ interface is accelerated due to the formation of surface dipoles and favorable energy band bending. As a result, these advances enable the demonstration of champion efficiency of 22.15% for CysHCl-processed LBG Sn–Pb PSCs with remarkable enhancement in both open-circuit voltage and fill factor. When paired with a wide-bandgap (WBG) perovskite subcell, a certified 25.7%-efficient all-perovskite monolithic tandem device is further demonstrated.

A comprehensive overview of the emerging perovskite-solar-cell-based photo-electrochemical device, including the configuration design, key parameters, working principle, integration strategies, electrode materials, and their performance evaluations, is highlighted. The existing challenges and future perspectives are provided for the ongoing research in this promising field.

Abstract

Metal halide hybrid perovskite solar cells (PSCs) have received considerable attention over the past decade owing to their potential for low-cost, solution-processable, earth-abundant, and high-performance superiority, increasing power conversion efficiencies of up to 25.7%. Solar energy conversion into electricity is highly efficient and sustainable, but direct utilization, storage, and poor energy diversity are difficult to achieve, resulting in a potential waste of resources. Considering its convenience and feasibility, converting solar energy into chemical fuels is regarded as a promising pathway for boosting energy diversity and expanding its utilization. In addition, the energy conversion–storage integrated system can efficiently sequentially capture, convert, and store energy in electrochemical energy storage devices. However, a comprehensive overview focusing on PSC-self-driven integrated devices with a discussion of their development and limitations remains lacking. Here, focus is on the development of representative configurations of emerging PSC-based photo-electrochemical devices including self-charging power packs, unassisted solar water splitting/CO₂ reduction. The advanced progresses in this field, including configuration design, key parameters, working principles, integration strategies, electrode materials, and their performance evaluations are also summarized. Finally, scientific challenges and future perspectives for ongoing research in this field are presented.

A layer of D-A-D small molecule film [triphenylamine-2,1,3-benzothiadiazole-triphenylamine (TBT)] is deposited at the NiO _x /MAPbI_3–x Cl _x interface, and the interface microstructure and crystallization control are realized. The interaction of TBT with perovskite results in a better alignment of energy levels and reduced interfacial defects, a satisfactory power conversion efficiency of 21.84%, and long-term stability of over 1000 h.

Nickel oxide (NiO _x ) is one of the most widely used inorganic hole transport materials for inverted perovskite solar cells (PSCs), which has the advantages of low cost, easy preparation, and good stability. However, the energy-level mismatch and interfacial redox reactions at the NiO _x /perovskite interface limit the performance of NiO _x -based PSCs. Herein, triphenylamine-2,1,3-benzothiadiazole-triphenylamine (TBT) small-molecule material is first used as an interfacial modification layer between NiO _x and perovskite. The deposition of TBT on NiO _x helps to hinder the contact between NiO _x and perovskite, improves the electrical conductivity, passivates interfacial defects, and inhibits the recombination of interfacial carriers. TBT makes the valance band top energy level of NiO _x better match that of perovskite and promotes the hole transfer at NiO _x /perovskite interface, and the hole transfer rate increases from 2.19 × 10¹⁰ to 4.12 × 10¹⁰ s⁻¹. The TBT-based device obtains a champion power conversion efficiency (PCE) of 21.84%, much higher than the control device (18.62%). Furthermore, the optimized device which is conserved in 30 ± 5% relative humidity and 25 °C environments more than 1000 h retains 90% of the initial efficiency. A effective strategy to improve the PCE and stability of NiO _x -based PSCs is provided.