Chen Weijie

This work introduces a low-temperature copper doping strategy to enhance the conductivity of atomic layer deposition NiO_x (ALD Cu:NiO_x) hole-transporting layers and suppress Ni³⁺ defects. This strategy improves the performance and scalability of textured perovskite/silicon tandems. As a result, an efficiency of 30.5% for 1-cm² tandems (certified 30.3%) and 26.4% for 8.89-cm² tandems is achieved.

Abstract

Perovskite tandem solar cells on textured silicon hold potential for surpassing single-junction limits and industrial compatibility. However, integrating hole-transporting layers (HTLs) onto textured silicon poses challenges in conformal coating, low-temperature fabrication, and perovskite solution process compatibility. Here, an atomic layer deposition (ALD) copper-doping process is introduced to fabricate low-temperature NiO_x HTLs (ALD Cu:NiO_x), tailored for textured tandems. Copper-doping reduces hydroxyl group content and Ni³⁺ defects, addressing the challenge of enhancing hole conductivity while mitigating recombination loss. This advancement enables to lower the post-annealing temperature from >300 to 200 °C, achieving compatibility with silicon heterojunction (SHJ) cells and boosting the power-conversion efficiency (PCE) of 1.65-eV p–i–n perovskite solar cells to 22.47%. Integrating ALD Cu:NiO_x beneath conventional self-assembled monolayer HTL on textured SHJ leads to notable PCE enhancements, from 28.6% to 30.5% for 1-cm² tandems (certified stabilized PCE of 30.04%) and from 23.9% to 26.4% for 8.89-cm² tandems. Following 1000 h of maximum-power-point (MPP) tracking, tandems maintain 95% of initial efficiency. Notably, losses in open-circuit voltage and PCE due to area upscaling reduced by over 20%, attributed to ALD Cu:NiO_x’s ability to enhance perovskite film wettability and minimize shunting on silicon pyramid texture, underscoring its impacts for textured tandem upscaling.

Publication date: October 2024

Source: Nano Energy, Volume 129, Part B

Author(s): Chao Gao, Haotian Zhang, Sheng Ma, Hongzhen Su, Huanpei Huang, Li He, Dezhao Zhang, Daxue Du, Hong Liu, Wenzhong Shen

Acetylcholine acts as a proficient “diver,” aiding in the reconstruction of the buried interface and significantly improving the overall quality of the top narrow-bandgap mixed tin–lead perovskite layers. As a result, single-junction narrow-bandgap perovskite solar cells and their 2-terminal tandems achieve stabilized power conversion efficiencies of 22.98% and 27.54%, respectively.

Abstract

Narrow-bandgap (NBG) mixed tin-lead (Sn-Pb) perovskite solar cells (PSCs) serve as crucial top subcells in all-perovskite tandem solar cells (TSCs). However, the prevalent use of poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) hole transport layers (HTLs) in NBG PSCs compromises device efficiency and stability. To address this, the study proposes a revitalizing strategy for the buried interface of Sn-Pb perovskites by directly immersing acetylcholine chloride (ACh) into PEDOT: PSS. ACh acts as a proficient “diver,” not only modulating the bottom PEDOT: PSS HTLs but also facilitating the reconstruction of the buried interface and significantly enhancing the quality of the top perovskite layers. This intervention with ACh prevents Sn²⁺ oxidation, mitigates buried defects, and encourages the growth of large, densely packed grains within Sn-Pb perovskites. Consequently, the optimized NBG PSCs exhibit significantly improved hole transport and reduced carrier recombination, achieving a steady-state efficiency of 22.98% with enhanced stability. Furthermore, these optimized NBG Sn-Pb cells enable highly efficient two-terminal and four-terminal all-perovskite TSCs, boasting steady-state efficiencies of 27.54% (certified at 26.41%) and 28.01%, respectively. This study emphasizes the importance of optimizing NBG PSCs through buried interface reconstruction, propelling the advancement of all-perovskite TSCs.

Ortho-, meta-, and para-isomers of fluorophenylethylammonium iodine (F-PEAI) are tested in constructing perovskite quantum wells (PQWs) for 3D perovskites. Among them, p-F-PEAI offers optimal charge distribution and minimal steric hindrance, enhancing PbI₂ interaction, as confirmed by TEM and GIWAXS. This results in improved surface passivation and charge transport. Inverted PSCs achieve a boosted PCE to 25.03% with enhanced stability.

Abstract

The photovoltaic performance of inverted perovskite solar cells (PSCs) is often hindered by trap-induced non-radiative recombination and photochemical degradation occurring at the upper interfaces and the grain boundaries of perovskite films. Herein, ortho-, meta-, and para-isomers of fluorophenylethylammonium iodine (F-PEAI) organic spacer molecules are evaluated for the construction of perovskite quantum wells (2D or quasi-2D, PQWs) to encapsulate 3D perovskites. Among the three variants, p-F-PEAI leads to the most symmetric charge distribution and the weakest steric hindrance which resulting in reinforced interactions with PbI₂ and perovskite, the enhanced out-of-plane orientation is confirmed by Grazing incidence wide-angle X-ray scattering (GIWAXS) results. Density functional theory and crystal orbital Hamilton population (COHP) calculations further confirm that p-F-PEAI engages most strongly with the perovskite structure. Moreover, transmission electron microscopy (TEM) characterization is used to illustrate that p-F-PEAI-assisted 2D PQWs effectively passivate both the grain boundaries and surfaces of perovskites. This configuration facilitates effective surface passivation, improves charge carrier transport, and significantly suppresses non-radiative recombination. The resultant inverted PSCs achieve an excellent power conversion efficiency (PCE) of 25.03% with a fill factor (FF) of 85.11%. The unencapsulated devices exhibit enhanced long-term stability under ambient environments and continuous light illumination.

A perovskite (PVSK) solar cell fracture model is developed to provide rapid screening of new candidate device layers, solar cell geometries, and processing conditions for both rigid glass and flexible substrates. This model directs research decisions to inhibit fracture-based degradation in PVSKs and provides guidance to improve the robustness of inherently fragile PVSK thin films.

Perovskite (PVSK) solar cells offer significant benefits over conventional silicon cells including low-cost solution processibility, minimal materials usage related to strong photon absorption in thin-film cell architectures, and a tunable bandgap. However, PVSK films are mechanically fragile, and fracture of PVSK layers and adjacent interfaces are a significant concern during fabrication, encapsulation, and operation. Herein, a thin-film mechanics fracture analysis tailored for p–i–n and n–i–p PVSK solar cells on both soda lime glass and polyimide substrates fabricated with three PVSK crystallization methods is presented. The role of thermal processing of each cell layer is explored to determine the maximum allowable temperature below which fracture is inhibited. In the analysis, the mechanics basis for processing and materials selection guidelines for preventing fracture in PVSK solar cells is provided.

A multiple dynamic hydrogen bonding network (i.e., dopamine-grafted polyacrylic acid (PAA-DA)) is developed. The mechanical stability of flexible perovskite solar cells (f-PSCs) is enhanced through simultaneously tuning the two essential parameters, namely Young's modulus and thermal expansion coefficient. The f-PSCs show a high efficiency of 23.02%, long-term operational stability, and superior mechanical stability.

Abstract

Flexible perovskite solar cells often experience constant or cyclic bending during their service life. Catastrophic failure of devices may occur due to the crack of polycrystalline perovskite films and delamination at the perovskite and the substrate interfaces, posing a significant stability concern. Here, a multiple dynamic hydrogen bonding polymer network is developed to enhance the mechanical strength of flexible perovskite solar cells in two ways. The main chain of poly(acrylic acid) decreases the mismatch of the coefficient of thermal expansion between the perovskite and the substrate by 16.7% through its flexibility and spatial occupation. The dopamine branch chains provide multiple dynamic hydrogen bonding sites, which contribute to increased energy dissipation upon stress deformation and reduce Young's modulus of perovskite by 54.3%. The inverted flexible perovskite solar cells achieve a champion power conversion efficiency of 23.02% and retain 81.3% of the initial PCE over 2000 h under continuous 1-sun equivalent illumination. Moreover, devices show excellent mechanical stability by remaining 90.2% of the original value after 5000 bending cycles.

A bridging molecule, (2-aminoethyl)phosphonic acid (AEP), is utilized to modify the buried SnO₂/perovskite interface in PSCs. The dual functionality of AEP with adjacent interface leads to significant benefits such as defects suppression, increased film quality, and interfacial charge extraction improvement. A power conversion efficiency (PCE) of 26.40% (certified at 25.98%) is achieved with ≈1400 h operational durability.

Abstract

The interface between the perovskite layer and electron transporting layer is a critical determinate for the performance and stability of perovskite solar cells (PSCs). The heterogeneity of the interface critically affects the carrier dynamics at the buried interface. To address this, a bridging molecule, (2-aminoethyl)phosphonic acid (AEP), is introduced for the modification of SnO₂/perovskite buried interface in n–i–p structure PSCs. The phosphonic acid group strongly bonds to the SnO₂ surface, effectively suppressing the surface carrier traps and leakage current, and uniforming the surface potential. Meanwhile, the amino group influences the growth of perovskite film, resulting in higher crystallinity, phase purity, and fewer defects. Furthermore, the bridging molecules facilitate the charge extraction at the interface, as indicated by the femtosecond transient reflection (fs-TR) spectroscopy, leading to champion power conversion efficiency (PCE) of 26.40% (certified 25.98%) for PSCs. Additionally, the strengthened interface enables improved operational durability of ≈1400 h for the unencapsulated PSCs under ISOS-L-1I protocol.

Benzaldehyde oxime is introduced into the mixed Sn−Pb perovskite precursor to inhibit the oxidation of Sn(II), which can also regulate the crystallization and improve the electronic structure of the perovskite film, ultimately resulting in enhanced long-term stability and performance of devices.

Abstract

Despite numerous studies have reported the inhibition of tin (II) oxidation in mixed tin-lead halide perovskite, there remains a dearth of mechanistic information regarding how tin (II) undergoes oxidation in the precursor solution, particularly in terms of the involvement of DMSO. We here take advantage of density functional theory (DFT) to uncover that SnI₂ can coordinate with DMSO and react with singlet oxygen, resulting in the generation of Sn (IV). Moreover, our DFT simulations reveal that benzaldehyde oxime (BZHO) competes with SnI₂ in reacting with oxygen through the Alder-ene reaction, hence effectively restraining the oxidation of tin (II), which is further verified by several experimental characterizations. Besides, the introduction of BZHO has also regulated the crystallization of the perovskite film and modified the electronic structure of the perovskite surface. As a result, the perovskite solar cells with the addition of BZHO demonstrate superior performance and operational stability, retaining 82 % of the initial PCE under continuous 1-sun illumination for 800 hours. Furthermore, the efficiency of all-perovskite tandem solar cells treated with BZHO reached 26.76 %. Therefore, this work presents a promising strategy for designing high-performance and stable all-perovskite tandem solar cells.

A two-terminal multijunction solar cell is subjected to current mismatch-induced reverse bias, potentially leading to shunt-like reverse breakdown. This is particularly critical in cells with more than two junctions, especially when subcells with low breakdown voltage, such as perovskites, are included. The possibility of junction breakdown during current–voltage measurements of perovskite/perovskite/silicon triple-junction solar cells through simulations and experimental demonstrations is investigated.

Perovskite-based triple-junction solar cells have recently gained significant attention and are rapidly developing, thanks to the insights gained from the advancement in its dual-junction counterparts. However, employing perovskite materials in multijunction solar cells with more than two junctions brings new challenges that have not yet been addressed. One aspect is the possibility of reverse bias breakdown of perovskite subcells during operation of the triple–junction device. This is more relevant for triple-junction solar cells because a higher reverse voltage might drop at perovskite subcells compared to the case of dual-junction solar cells. Herein, the breakdown voltages of the two perovskite subcells in perovskite/perovskite/silicon triple-junction solar cells are determined by progressively increasing the reverse bias applied to the subcells in a single-junction architecture during current–voltage measurements and monitoring the appearance of shunts using illuminated lock-in thermography measurements. Furthermore, to analyze the effect on the final triple–junction solar cell, the triple-junction device is brought in different current limitation conditions. It is shown that the subcell breakdown can happen during the operation of the triple-junction solar cell, especially for the case where the perovskite top cell is limiting the overall current of the device. This effect is less severe when the middle perovskite cell limits the current due to the absence of a direct contact with the silver metallization which has shown to be the major degradation site during reverse biasing of perovskite solar cells. Finally, there is no concern regarding breakdown of the silicon bottom cell due to the higher breakdown voltage of silicon compared to perovskite.

The study explores alkali carbonates (Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, and Cs₂CO₃), highlighting alkali metal cations' crucial role in suppressing oxygen vacancies. Rb₂CO₃ emerges as an optimal interfacial material, boosting perovskite solar cell efficiency to 22.10% with enhanced stability. These valuable insights emphasize the critical importance of alkali metal cation selection in achieving effective and stable perovskite solar cell interfaces.

Abstract

Effectively suppressing nonradiative recombination at the SnO₂/perovskite interface is imperative for perovskite solar cells. Although the capabilities of alkali salts at the SnO₂/perovskite interface have been acknowledged, the effects and optimal selection of alkali metal cations remain poorly understood. Herein, a novel approach for obtaining the optimal alkali metal cation (A-cation) at the interface is investigated by comparatively analyzing different alkali carbonates (A₂CO₃; Li₂CO₃, Na₂CO₃, K₂CO₃, Rb₂CO₃, and Cs₂CO₃). Theoretical calculations demonstrate that A₂CO₃ coordinates with undercoordinated Sn and O on the surface, effectively mitigating oxygen vacancy (V_O) defects with increasing A-cation size, whereas Cs₂CO₃ exhibits diminished preferability owing to enhanced steric hindrance. The experimental results highlight the crucial role of Rb₂CO₃ in actively passivating V_O defects, forming a robust bond with SnO₂, and facilitating Rb⁺ diffusion into the perovskite layer, thereby enhancing charge extraction, alleviating deep-level trap states and structural distortion in the perovskite film, and significantly suppressing nonradiative recombination. X-ray absorption spectroscopy analyses further reveal the effect of Rb₂CO₃ on the local structure of the perovskite film. Consequently, a Rb₂CO₃-treated device with aperture area of 0.14 cm² achieves a notable efficiency of 22.10%, showing improved stability compared to the 20.11% achieved for the control device.

We propose the utilization of an aniline-derived molecule, namely 2-methoxy-5-trifluoromethylaniline (MFA), as an additive for the fabrication of CsPbI_3-xBr_x solar cells. The incorporation of MFA into the perovskite film can effectively enhance the energy barrier for defect formation and ion migration. This customized strategy allows us to achieve a champion power conversion efficiency (PCE) as high as 22.14 % and significantly improved environmental stability and photostability.

Abstract

The characteristics of the soft component and the ionic-electronic nature in all-inorganic CsPbI_3-xBr_x perovskite typically lead to a significant number of halide vacancy defects and ions migration, resulting in a reduction in both photovoltaic efficiency and stability. Herein, we present a tailored approach in which both anion-fixation and undercoordinated-Pb passivation are achieved in situ during crystallization by employing a molecule derived from aniline, specifically 2-methoxy-5-trifluoromethylaniline (MFA), to address the above challenges. The incorporation of MFA into the perovskite film results in a pronounced inhibition of ion migration, a significant reduction in trap density, an enhancement in grain size, an extension of charge carrier lifetime, and a more favorable alignment of energy levels. These advantageous characteristics contribute to achieving a champion power conversion efficiency (PCE) of 22.14 % for the MFA-based CsPbI_3-xBr_x perovskite solar cells (PSCs), representing the highest efficiency reported thus far for this type of inorganic metal halide perovskite solar cells, to the best of our knowledge. Moreover, the resultant PSCs exhibits higher environmental stability and photostability. This strategy is anticipated to offer significant advantages for large-area fabrication, particularly in terms of simplicity.

This study leverages molecular dynamics simulation and experimental characterization to elucidate the effects of ligand chemistry on suppressing ion transport in 2D hybrid-inorganic perovskites. Analyses reveal that increasing stiffness and length of ligands generally inhibits ion transport, while increasing ligand polarization generally enhances it. These insights provide possible principles for designing passivation materials to enhance the stability of perovskite photovoltaics.

Abstract

2D hybrid organic–inorganic perovskites are potentially promising materials as passivation layers that can enhance the efficiency and stability of perovskite photovoltaics. The ability to suppress ion transport is proposed as a stabilization mechanism, yet an effective characterization of relevant modes of halide diffusion in 2D perovskites is nascent. In light of this knowledge gap, molecular dynamics simulations with enhanced sampling and experimental validation to systematically characterize how ligand chemistry in seven (R-NH₃)₂PbI₄ systems impacts halide diffusion, particularly in the out-of-plane direction is combined. It is found that increasing stiffness and length of ligands generally inhibits ion transport, while increasing ligand polarization generally enhances it. Structural and energetic analyses of the migration pathways provide quantitative explanations for these trends, which reflect aspects of the disorder of the organic layer. Overall, this mechanistic analysis greatly enhances the current understanding of halide migration in 2D hybrid organic–inorganic perovskites and yields insights that can inform the design of future passivation materials.

Room-temperature ripening induced by the synergy of hygroscopic salt and moisture is reported for preparing efficient hole-conductor-free mesoscopic perovskite solar cells with efficiency surpassing 20 %. The post-treatment enables significant secondary crystallization of perovskite through moisture absorption which liquefies the grain boundary and activates sufficient mass transfer by offering channels and promoting desired dissolution.

Abstract

Solution-processed perovskite films generally possess small grain sizes and high density of grain boundaries, which intensify non-radiative recombination of carriers and limit the power conversion efficiency (PCE) of solar cells. In this study, we report the room-temperature ripening enabled by the synergy of hygroscopic salts and moisture in air for efficient hole-conductor-free printable mesoscopic perovskite solar cells (p-MPSCs). Treating perovskite films with proper hygroscopic salts in damp air induces obvious secondary recrystallization, which coarsens the grains size from hundreds of nanometers to several micrometers. It's proposed that the hygroscopic salt at grain boundaries could absorb moisture and form a complex which could not only serve as mass transfer channel but also assist in the dissolution of perovskite grains. This activates mass transfer between small grains and large grains since they possess different solubilities, and thus ripens the perovskite film. Consequently, p-MPSCs treated with the hygroscopic salt of NH₄SCN show an improved power conversion efficiency of 20.13 % from 17.94 %, and maintain >98 % of the initial efficiency under maximum power point tracking at 55±5 °C for 350 hours.

This study investigates two novel carbazole-diphenylamine-based hole transport materials (HTMs), characterized by the presence of two isomeric substituent functional groups on their side chains. Both theoretical and experimental studies indicate that the functionalization of these substituent groups enhances intermolecular and interfacial interactions in the HTMs. Consequently, perovskite solar cell devices based on RQ8 exhibit higher power conversion efficiency compared to those based on RQ7.

Developing potential hole transport materials (HTMs) is an effective approach to reduce carrier nonradiative recombination and improve the efficiency of perovskite solar cells (PSCs). To investigate the intermolecular and interfacial interactions of HTMs in PSC devices, two molecules (RQ7 and RQ8) with substituent group functionalization are designed by isomerizing -F and -SMe in the para- and ortho-positions on the side chain of carbazole diphenylamine-based HTMs. Theoretical simulations indicate that the functionalization of substituent groups in HTMs alters their dipole moments and electronic structures, as well as their intermolecular interactions, hole transport capabilities, and interfacial interactions at the HTMs/perovskite interface. Experimental results show that RQ8 exhibited higher hole mobility, better film-forming ability, and reduced electron-hole recombination, resulting in RQ8-based PSC devices achieving a higher power conversion efficiency than those based on RQ7. Herein, it is demonstrated that isomerous functionalization of substituent groups in carbazole diphenylamine-based HTMs is a feasible strategy for controlling and regulating the intermolecular and interfacial interactions of HTMs in PSC applications.

Etidronic acid forms a bridging layer at SnO₂/FAPbI₃ interface through multidentate anchoring on SnO₂. The presence of the EA bridging layer can significantly enhance the phase stability of the FAPbI₃ film under high humidity conditions, which is due to its robust bridging structure and the interaction between the EA and the [PbI₆]⁴⁻ octahedron.

Abstract

Pure FAPbI₃-based, with FA being formamidinium, perovskite solar cells (PSCs) have garnered worldwide recognition for their exceptional efficiency. However, the phase stability of FAPbI₃ is still a big obstacle in this area, because the ordinary strategy using MA⁺, Br⁻, Cs⁺ to stabilize α-FAPbI₃ phase can cause the bandgap change and ion migration. Herein, a new strategy is introduced to improve the α-FAPbI₃ phase stability by using a self-assembled bridging layer at the buried interface of FAPbI₃ perovskite in the n–i–p solar cell structure. A series of multidentate bisphosphonic acid molecules are screened and demonstrate that etidronic acid (EA) with the smallest steric hindrance behaves the best. The four P-OH groups can first form multidentate anchors on SnO₂ while the remaining unanchored ─OH and P═O groups can form strong interaction between I⁻ and Pb²⁺. Thus, a strong and stable bridging layer is formed, which greatly increases the energy barrier of phase transition of FAPbI₃. As a result, the pure FAPbI₃-based (MA⁺, Br⁺, Cs⁺-free system) n–i–p device reached an impressive power conversion efficiency of 24.2% with good stability. Furthermore, the strong interaction between EA and Pb²⁺ can greatly reduce lead leakage in harsh conditions.

A dipole interlayer such as morpholinium bromide (MLBr) between C₆₀ and a 1.67 eV perovskite layer is effective in defect passivation and energy band alignment for charge extraction. Champion single junction and 1 cm² perovskite-Si tandem devices produced PCE's of 21.9% and 28.8%, respectively. Encapsulated tandems demonstrated excellent stability under continuous 1 sun illumination for 1000 h and retained 97% of initial PCE after 400 thermal cycles test (between −40 and 85 °C), twice the length of the IEC61215 Thermal Cycling test standard.

Abstract

C₆₀ is a widely used electron selective material for p–i–n perovskite cells, however, its energy level does not match well with that of a wide-bandgap perovskite, resulting in low open-circuit voltage (V_OC) and fill factor (FF). To overcome this issue, ultra-thin LiF has been widely used as an interlayer between C₆₀ and perovskite layers facilitating efficient electron extraction but resulting in instability. In this work, the use of a piperidinium bromide (PpBr) is reported as an interlayer between C₆₀ and perovskite, and the interlayer further is optimized by introducing an additional oxygen atom on the opposite side of the NH₂ ⁺. This results in morpholinium bromide (MLBr) with increased dipole moment. Because of this, MLBr is highly effective in minimizing the energy band mismatch between perovskite and C₆₀ layer for electron extraction while at the same time passivating defects. The champion single junction 1.67 eV MLBr solar cell produced a PCE of 21.9% and the champion monolithic MLBr perovskite-Si tandem cell produced a PCE of 28.8%. Most importantly, both encapsulated MLBr and PpBr devices retain over 97% of their initial efficiency after 400 thermal cycles (between −40 and 85 °C), twice the number of cycles specified by the International Electrotechnical Commission (IEC) 61215 photovoltaic module standard.

A highly crystalline self-assembled multilayer (SAMUL) that is fundamentally different from the conventional monolayer or disordered bilayer used for hole-extraction in inverted perovskite solar cells (PSCs). A detailed structure-property-performance relationship of molecules used for SAMUL is established through a systematic study of their crystallinity, molecular packing, and hole-transporting properties. The CbzNaphPPA-based SAMUL with the highest crystallinity and hole mobility derived from the ordered H-aggregation, which resulted in a very impressive power conversion efficiency (PCE) of 26.07 %. Additionally, a record-high PCE of 23.50 % could be achieved by adopting a thermally evaporated SAMUL. This greatly simplifies and broadens the scope for SAM to be used for large-area devices on diverse substrates.

Abstract

We report a highly crystalline self-assembled multilayer (SAMUL) that is fundamentally different from the conventional monolayer or disordered bilayer used for hole-extraction in inverted perovskite solar cells (PSCs). The SAMUL can be easily formed on ITO substrate to establish better surface coverage to enhance the performance and stability of PSCs. A detailed structure-property-performance relationship of molecules used for SAMUL is established through a systematic study of their crystallinity, molecular packing, and hole-transporting properties. These SAMULs are rationally optimized by varying their molecular structures and deposition methods through thermal evaporation or spin-coating for fabricating PSCs. The CbzNaphPPA-based SAMUL was chosen for fabricating inverted PSCs due to it exhibiting the highest crystallinity and hole mobility which is derived from the ordered H-aggregation. This resulted in a remarkably high fill factor of 86.45 %, which enables a very impressive power conversion efficiency (PCE) of 26.07 % to be achieved along with excellent device stability (94 % of its initial PCE retained after continuous operation for 1200 h under 1-sun irradiation at maximum power point at 65 °C). Additionally, a record-high PCE of 23.50 % could be achieved by adopting a thermally evaporated SAMUL. This greatly simplifies and broadens the scope for SAM to be used for large-area devices on diverse substrates.

Nature Communications, Published online: 24 July 2024; doi:10.1038/s41467-024-49751-7

Nature Materials, Published online: 23 July 2024; doi:10.1038/s41563-024-01945-6

In situ removable solid additives optimize active layer and cathode interlayer to achieve high-performance organic solar cells. The CBB- and CIB-treated PDINN interlayers suppress non-radiative recombination greatly and achieve higher open-circuit voltage, which affords D18:L8-BO based binary OSCs with unusual efficiencies of 19.38% and 19.26%, respectively, along with outstanding fill factors of 80.98% and 81.37%.

Abstract

In situ removable (ISR) solid additive can employ cold sublimation process to optimize active layer morphology for organic solar cells (OSCs), thus remaining unique potential. Herein, a feasible guideline is proposed to discover a new ISR solid additive 1-bromo-4-chlorobenzene (CBB), whose removing time (T _R) is between those of reported ISR solid additives 1,4-dichlorobenzene (DCB) and 1-chloro-4-iodobenzene (CIB). The CBB with a moderate T _R is beneficial for affording the optimal active layer morphology and achieving the highest power conversion efficiency (PCE) of 18.58% for D18:L8-BO binary active layer, as supported by the most efficient exciton splitting, the fastest exciton transfer, and the most balanced carrier transports. Due to the unique ISR ability, DCB, CBB, and CIB are further proposed to optimize the aggregation of PDINN cathode interlayer. Particularly, the CBB- and CIB-treated PDINN interlayers afforded the D18:L8-BO based binary OSCs with excellent PCEs of 19.38% and 19.26%, along with remarkable fill factors of 80.98% and 81.37%, respectively. The CBB- and CIB-treated PDINN interlayers can suppress non-radiative recombination of the devices, resulting in higher open-circuit voltage. This work not only provides an effective approach to flourish ISR solid additives but also expands the application of the ISR solid additive in OSCs.

Publication date: November 2024

Source: Journal of Energy Chemistry, Volume 98

Author(s): Boyuan Hu, Jian Zhang, Yulin Yang, Yayu Dong, Jiaqi Wang, Wei Wang, Xingrui Zhang, Kaifeng Lin, Debin Xia

Publication date: 16 October 2024

Source: Joule, Volume 8, Issue 10

Author(s): Oussama Er-raji, Mohamed A.A. Mahmoud, Oliver Fischer, Alexandra J. Ramadan, Dmitry Bogachuk, Alexander Reinholdt, Angelika Schmitt, Bhushan P. Kore, Thomas William Gries, Artem Musiienko, Oliver Schultz-Wittmann, Martin Bivour, Martin Hermle, Martin C. Schubert, Juliane Borchert, Stefan W. Glunz, Patricia S.C. Schulze

P₂S₅ was introduced into the Cu-Zn-Sn-S precursor solution to optimize grain growth and reduce defect density of Cu₂ZnSn(S,Se)₄ absorber. The results demonstrated that P₂S₅ molecule can coordinate with the metal cation sites of precursor films, especially more liable to the Zn²⁺, thereby effectively passivating the Zn-related defects. The power conversion efficiency has conspicuously climbed from 11.28% to 14.36%, making it one of the most high-efficiency kesterite solar cells.

Abstract

It has been validated that enhancing crystallinity and passivating the deep-level defect are critical for improving the device performance of kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells. Coordination chemistry interactions within the Cu-Zn-Sn-S precursor solution play a crucial role in the management of structural defects and the crystallization kinetics of CZTSSe thin films. Therefore, regulating the coordination environment of anion and cation in the precursor solution to control the formation process of precursor films is a major challenge at present. Herein, a synergetic crystallization modulation and defect passivation method is developed using P₂S₅ as an additive in the CZTS precursor solution to optimize the coordination structure and improve the crystallization process. The alignment of theoretical assessments with experimental observations confirms the ability of the P₂S₅ molecule to coordinate with the metal cation sites of CZTS precursor films, especially more liable to the Zn²⁺, effectively passivating the Zn-related defects, thereby significantly reducing the defect density in CZTSSe absorbers. As a result, the device with a power conversion efficiency of 14.36% has been achieved. This work provides an unprecedented strategy for fabricating high-quality thin films by anion-coordinate regulation and a novel route for realizing efficient CZTSSe solar cells.

Mixed tin-lead-based perovskite solar cells with ideal bandgap (1.2 eV) develop rapidly, while the top interface defects and Sn oxidation cannot be solved simultaneously. It is found cross-linkable [6,6]-phenyl-C61-butyric styryl dendron ester (C-PCBSD) can coordinate with perovskite and optimize the interface and bulk of perovskite. This work demonstrates the optimization effect of C-PCBSD on perovskite interface and bulk.

Abstract

Mixed tin-lead (Sn-Pb) perovskites have attracted the attention of the community due to their narrow bandgap, ideal for photovoltaic applications, especially tandem solar cells. However, the oxidation and rapid crystallization of Sn²⁺ and the interfacial traps hinder their development. Here, cross-linkable [6,6]-phenyl-C₆₁-butyric styryl dendron ester (C-PCBSD) is introduced during the quenching step of perovskite thin film processing to suppress the generation of surface defects at the electron transport layer interface and improve the bulk crystallinity. The C-PCBSD has strong coordination ability with Sn²⁺ and Pb²⁺ perovskite precursors, which retards the crystallization process, suppresses the oxidation of Sn²⁺, and improves the perovskite bulk and surface crystallinity, yielding films with reduced nonradiative recombination and enhanced interface charge extraction. Besides, the C-PCBSD network deposited on the perovskite surface displays superior hydrophobicity and oxygen resistance. Consequently, the devices with C-PCBSD obtain PCEs of up to 23.4% and retained 97% of initial efficiency after 2000 h of storage in a N₂ atmosphere.

Metal halide perovskites (MHPs) photocatalysts are bi-functionalized with lead sulfide (PbS) and amorphous molybdenum sulfide (MoS_x) co-catalysts on the surface. PbS can passivates the defects of MHPs and MoS_x provides active sites for hydrogen evolution reaction (HER), thus synergistically enhancing the charge transport efficiency and HER catalysis and achieving a superior solar-to-chemical (STC) energy conversion efficiency of 4.63 %.

Abstract

Metal halide perovskites (MHPs) have emerged as attractive candidates for producing green hydrogen via photocatalytic pathway. However, the presence of abundant defects and absence of efficient hydrogen evolution reaction (HER) active sites on MHPs seriously limit the solar-to-chemical (STC) conversion efficiency. Herein, to address this issue, we present a bi-functionalization strategy through decorating MHPs with a molecular molybdenum-sulfur-containing co-catalyst precursor. By virtue of the strong chemical interaction between lead and sulfur and the good dispersion of the molecular co-catalyst precursor in the deposition solution, a uniform and intimate decoration of the MHPs surface with lead sulfide (PbS) and amorphous molybdenum sulfide (MoS_x) co-catalysts is obtained simultaneously. We show that the PbS co-catalyst can effectively passivate the Pb-related defects on the MHPs surface, thus retarding the charge recombination and promoting the charge transfer efficiency significantly. The amorphous MoS_x co-catalyst further promotes the extraction of photogenerated electrons from MHPs and facilitates the HER catalysis. Consequently, drastically enhanced photocatalytic HER activities are obtained on representative MHPs through the synergistic functionalization of PbS and MoS_x co-catalysts. A solar-to-chemical (STC) conversion efficiency of ca. 4.63 % is achieved on the bi-functionalized FAPbBr_3-xI_x (FA=CH(NH₂)₂), which is among the highest values reported for MHPs.

Publication date: October 2024

Source: Nano Energy, Volume 129, Part A

Author(s): Luye Cao, Hengyuan Zhang, Xiaoyang Du, Hui Lin, Caijun Zheng, Gang Yang, Min Deng, Xiaopeng Xu, Silu Tao, Qiang Peng