Chen Weijie

A cross-linked film, QBr-PEI-50, based on a quinoidal compound and polyethylenimine has been developed. This film exhibits high electrical conductivity and exceptional stretchability. When utilized as the electron transport layer in inverted organic solar cells (OSCs), it achieved a power conversion efficiency of 18.27 % with impressive stability. Additionally, fully stretchable inverted OSCs fabricated with QBr-PEI-50 demonstrated a PCE of 14.01 %.

Abstract

The photocatalytic activity and inherent brittleness of ZnO, which is commonly used as an electron transport layer (ETL) in inverted organic solar cells (OSCs), have impeded advancements in device stability and the development of fully stretchable OSCs. In this study, an intrinsically stretchable ETL for inverted OSCs through a side-chain cross-linking strategy has been developed. Specifically, cross-linking between bromine atoms on the side chains of a quinoidal compound and the amino groups in polyethylenimine resulted in a film, designated QBr-PEI-50, with high electrical conductivity (0.049 S/m) and excellent stretchability (crack-onset strain>45 %). When used as the ETL in inverted OSCs, QBr-PEI-50 was markedly superior to ZnO in terms of device performance and stability, yielding a power conversion efficiency (PCE) of 18.27 % and a T ₈₀ lifetime exceeding 10000 h. Moreover, incorporation of QBr-PEI-50 in fully stretchable inverted OSCs yielded a PCE of 14.01 %, and 80 % of the initial PCE was maintained after 21 % strain, showcasing its potential for wearable electronics.

In this study, we utilize BaBr₂ to innovatively regulate the heterogeneous nucleation kinetics of Sb₂(S,Se)₃ film synthesized via hydrothermal deposition approach. This strategy optimizes the crystalline orientation and defect features, suppressing non-radiative recombination. Thus, the champion device presents a PCE of 10.12 %.

Abstract

Antimony selenosulfide (Sb₂(S,Se)₃) has obtained widespread concern for photovoltaic applications as a light absorber due to superior photoelectric features. Accordingly, various deposition technologies have been developed in recent years, especially hydrothermal deposition method, which has achieved a great success. However, device performances are limited with severe carrier recombination, relating to the quality of absorber and interfaces. Herein, bulk and interface defects are simultaneously suppressed by regulating heterogeneous nucleation kinetics with barium dibromide (BaBr₂) introduction. In details, the Br adsorbs and dopes on the polar planes of cadmium sulfide (CdS) buffer layer, promoting the exposure of nonpolar planes of CdS, which facilitates the favorable growth of [hk1]-Sb₂(S,Se)₃ films possessing superior crystallinity and small interface defects. Additionally, the Se/S ratio is increased due to the replacement of Se by Br, causing a downshift of the Fermi levels with a benign band alignment and a shallow-level defect. Moreover, Ba²⁺ is located at grain boundaries by coordination with S and Se ions, passivating grain boundary defects. Consequently, the efficiency is increased from 7.70 % to 10.12 %. This work opens an avenue towards regulating the heterogeneous nucleation kinetics of Sb₂(S,Se)₃ film deposited via hydrothermal deposition approach to optimize its crystalline orientation and defect features.

Lanthanide element Sm with a unique electronic structure has been introduced into SnO₂ electron transport layer (ETL), passivating oxygen vacancy defects, optimizing energetic alignment, and promoting perovskite crystallization. The synergistic optimization effect of Sm doping has been demonstrated, leading to perovskite crystallization and enhanced interfacial charge transport. This study pioneers Sm³⁺ doping in SnO₂ ETL, achieving 24.10% perovskite solar cells efficiency.

Tin oxide (SnO₂) has demonstrated significant potential as an electron transport layer (ETL) owing to its low-temperature processing in perovskite solar cells (PSCs). However, the poor energy-level alignment and the presence of interface defects between the SnO₂ and perovskite layer aggravate the power conversion efficiency (PCE) of the PSCs. Herein, heterovalent samarium cation (Sm³⁺) is deliberately doped into SnO₂, optimizing the energy-level alignment between SnO₂ and the perovskite layer, and effectively passivating the oxygen vacancy defects on the surface of SnO₂. Experimental and theoretical conclusions reveal that Sm-doping successfully passivates the defects in the ETL and improves the perovskite crystal quality, thereby reducing interface charge recombination, and enhancing electron extraction from perovskite to the SnO₂ layer. Consequently, the optimized Sm-doped SnO₂-based PSCs achieve a PCE of 24.10% with a V _OC of 1.174 V, negligible hysteresis, and improved durability under ambient conditions.

Halogen-free photoactive layer-based organic solar cells deliver a champion efficiency of 13.12% for inverted nonhalogenated cells (ITO/AZO/PBDB-T:BTP-M/MoO₃/Ag). Moreover, superior thermal stability is demonstrated by the retention of 89% of the initial efficiency after 900 h of heat stress (85 °C, N₂). The study illustrates the principle and potential of nonhalogenated organic solar cells to achieve efficient and stable performance.

While state-of-the-art organic photovoltaics (OPVs) have been achieved by halogen modification strategies for active layer materials, the stability of these OPVs can be compromised by the presence of halogen ions at the interface and within the photoactive layer. Herein, halogen-free photoactive layer-based OPV cells are fabricated and systematically studied to understand and explore the working principle and potential of this class of OPV devices. For the first time, a champion efficiency of 13.12% is achieved for the inverted device (ITO/AZO/AL/MoO₃/Ag) based on the nonhalogenated photoactive layer PBDB-T:BTP-M. Superior metal electrode stability is confirmed for the unencapsulated PBDB-T:BTP-M devices aged at 85 °C in the air atmosphere compared to the halogenated PM6:Y6 devices. Specifically, better thermal stability is verified for the nonhalogenated device without 1-chloronaphthalene (1-CN) additive compared to the device with 1-CN additive, with 89% of the initial efficiency retained after being aged for 900 h at 85 °C in the N₂ atmosphere. These results evidence the halogen/halide impacts on device stability and demonstrate the potential for nonhalogenated OPVs to achieve efficient and stable performance, benefiting the development and practical application of this technology.

This study boosts the stability and safety of perovskite solar cells by doping Spiro-OMeTAD with Tp-Azo-COF. The treated cells achieve 24.25% efficiency in small devices and 21.96% in larger modules, demonstrating reduced lead leakage and enhanced durability. This marks a key advance in sustainable perovskite photovoltaics.

Abstract

Despite significant advances in perovskite solar cells (PeSCs), the operational instability and susceptibility to Pb leakage of PeSCs severely limit their widespread application. To address these issues, this study investigates the effect of doping the Spiro-OMeTAD hole-transporting layer (HTL) with a chemically-modified 2D conjugated covalent organic framework (Tp-Azo-COF) on the photovoltaic performance and stability of PeSCs. Enriched with abundant carbonyl (C═O) groups and azo (N═N) nodes, Tp-Azo-COF has excellent chelation and adsorption capabilities, and experimental results confirm that Tp-Azo-COF effectively decreases Pb leakage and Li-ion migration, improving the environmental safety and operational stability of PeSCs. The optimized PeSCs (0.12 cm²) exhibit an efficiency of 24.25%, a new benchmark for COF-modified devices, and maintain robust performance in large-area modules (18 cm²) with an efficiency of 21.96%. Under accelerated aging tests, including continuous light irradiation at maximum power point tracking for 980 h, the module demonstrated exceptional durability, with near-100% efficiency retention. The COF doping strategy developed in this study significantly enhances operational stability and minimizes Pb leakage in PeSCs, paving the way for the sustainable, large-scale deployment of perovskite photovoltaics.

A solvent-induced copper vacancy strategy is presented to tune the Fermi level and conductivity of copper(I) thiocyanate (CuSCN) thin films, leading to improved energy alignment and a remarkable power-conversion efficiency of 19.10% efficiency in ternary OSCs.

Abstract

Copper(I) thiocyanate (CuSCN) is a prominent wide-bandgap p-type semiconductor with desirable transparency and chemical robustness. Whereas intrinsic limitations, such as its relatively low Fermi level (E _F) and modest electrical conductivity, have impeded its broader application in organic solar cells (OSCs). This study introduces a novel approach to modify the electronic properties of CuSCN by inducing copper vacancies through the use of specific solvent mixtures, thereby enhancing its suitability for OSCs. The effects of two solvent mixtures, methanol/ammonia (CH₃OH/NH₄OH) and dimethyl sulfoxide/N,N-Dimethylformamide (DMSO/DMF) is have systematically investigated, on the CuSCN layer. The findings reveal that these solvent systems induce a higher concentration of copper vacancies within the CuSCN film, resulting in a significant reduction of the E _F and a substantial increase in electrical conductivity. These modifications have led to the improved energy level alignment with the PM6:L8-BO:BTP-eC9 blended photoactive layers, culminating in a marked enhancement of the power-conversion efficiencies of 19.10% for the DMSO/DMF processed CuSCN layer. Additionally, it has observed enhanced shelf/thermal stability and thickness tolerance of OSCs based on these CuSCN films. This work not only presents a novel strategy for modifying the performance characteristics of CuSCN but also underscores its potential to contribute to the advancement of photovoltaic technologies.

To achieve efficient charge extraction and trap passivation, a A-D-A-type DTPA-CN is designed as a multifunctional interfacial layer for n-i-p perovskite solar cells. The DTPA-CN-treated device exhibits a champion PCE of 25.00%, which is significantly higher than that of the control device (22.78%). After 2,040 h of storage in a glove box, the device maintains 90% of its initial efficiency.

Abstract

Interfacial defects and energy level mismatches between the perovskite and 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD) layers heavily hinder charge transfer, limiting the efficiency and stability of n-i-p perovskite solar cells (PSCs). Herein, D-type TPA, D-A-type TPA-CN, and A-D-A-type DTPA-CN with triphenylamine units and different interfacial dipoles are designed as multifunctional interfacial layers for n-i-p PSCs. Among the three molecules, A-D-A-type DTPA-CN has the largest dipole moment, hole transporting capability, and hydrophobicity, and therefore the strongest passivation of interfacial defects and the best carrier extraction efficiency can be observed. As a result, the DTPA-CN-treated device achieves a champion power conversion efficiency (PCE) of 25.00%, as compared to the control device (22.78%). Moreover, the long-term stability of the unencapsulated device is significantly improved. After 2,040 h of storage in a nitrogen glove box, the device maintains over 90% of its initial efficiency, while only 61% for the control device. The work indicates that simultaneous improvement of trap passivation and hole extraction is critical for achieving highly efficient and stable n-i-p PSCs.

The dual role of hydrazide derivatives in inhibiting iodide oxidation and passivating crystal termination defects enhances the power conversion efficiency of the printable mesoscopic perovskite solar cells from 18.66% to 20.30%, and the resulted device maintains 90% of its initial efficiency after 500 h tacking at maximum power point.

Abstract

The oxidation of iodide ions during annealing in air and rich defects generated at crystal terminations in perovskite are major limitations for achieving high photovoltaic performance in printable mesoscopic perovskite solar cells (p-MPSCs). Here, the dual role of hydrazide derivatives in inhibiting iodide oxidation and passivating crystal termination defects is reported and how the dual role is affected by the substituent is studied. It's found that varying the hydrazide derivative from formylhydrazine (FH) to benzhydrazide (BH) and then to 4-tert-butylbenzhydrazide (TBBH) by introducing phenyl and 4-tert-butylphenyl substituents enhances the electron donating ability of hydrazides due to substituent electronic effect. The tailored hydrazides present enhanced iodide oxidation suppression and defect passivation capabilities, which lowers the trap density of perovskite in p-MPSCs significantly. As the most effective additive, TBBH improves the power conversion efficiency of the p-MPSC from 18.66% to 20.30%, and the resulted device maintains 90% of its initial efficiency after 500 h tacking at maximum power point at 55 ± 5 °C under simulated 1 sun illumination.

ZnO, SrTiO₃ (STO), WO₃ (TO), and Zn₂SnO₄ (ZTO) nanoparticles (NPs) are synthesized using a simple sol-gel route. The champion device with ITO/ZnO/ZTO/PbS-FABr/PbS-EDT/NiO/Au configuration achieved a highest power conversion efficiency (PCE) of 15.28% and an FF of 74.5%. Furthermore, ZnO/ZTO-based PbS CQDSCs show a long-term stability of over 80 days.

Abstract

In order to enhance the overall efficiency of colloidal quantum dots solar cells, it is crucial to suppress the recombination of charge carriers and minimize energy loss at the interfaces between the transparent electrode, electron transport layer (ETL), and colloidal quantum dots (CQDs) light-absorbing material. In the current study, ZnO/SrTiO₃ (STO), ZnO/WO₃ (TO), and ZnO/Zn₂SnO₄ (ZTO) bilayers are introduced as an ETL using a spin-coating technique. The ZTO interlayer exhibits a smoother surface with a root-mean-square (RMS) value of ≈ 3.28 nm compared to STO and TO interlayers, which enables it to cover the surface of the ITO/ZnO substrate entirely and helps to prevent direct contact between the CQDs absorber layer and the ITO/ZnO substrate, thereby effectively preventing efficient charge recombination at the interfaces of the ETL/CQDs. Furthermore, the ZTO interlayer possesses superior electron mobility, a higher visible light transmission, and a suitable energy band structure compared to STO and TO. These characteristics are advantageous for extracting charge carriers and facilitating electron transport. The PbS CQDs solar cell based on the ITO/ZnO/ZTO/PbS-FABr/PbS-EDT/NiO/Au device configuration exhibits the highest efficiency of 15.28%, which is significantly superior than the ITO/ZnO/PbS-FABr/PbS-EDT/NiO/Au solar cell device (PCE = 14.38%). This study is anticipated to offer a practical approach to develop ultrathin and compact ETL for highly efficient CQDSCs.

Herein, highly efficient Sn-Pb PSCs are achieved by using green histidine (HIS) doped in PEDOT: PSS. HIS induces preferential crystal orientation of the perovskite films, reducing the residual strain. The modified device achieves a satisfactory 21.46% of PCE. Moreover, HIS neutralizes the acidity of PEDOT: PSS and passivates the perovskite defects, leading to significant enhancement in stability.

Abstract

Mixed tin-lead perovskite solar cells (PSCs) have garnered much attention for their ideal bandgap and high environmental research value. However, poly (3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS), widely used as a hole transport layer (HTL) for Sn-Pb PSCs, results in unsatisfactory power conversion efficiency (PCE) and long-term stability of PSCs due to its acidity and moisture absorption. A synergistic strategy by incorporating histidine (HIS) into the PEDOT: PSS HTL is applied to simultaneously regulate the nucleation and crystallization of perovskite (PVK). HIS neutralizes the acidity of PEDOT: PSS and enhances conductivity. Especially, the coordination of the C═N and -COO⁻ functional groups in the HIS molecule with Sn²⁺ and Pb²⁺ induces vertical growth of PVK film, resulting in the release of residual surface stress. Additionally, this strategy also optimizes the energy level alignment between the perovskite layer and the HTL, which improves charge extraction and transport. With these cooperative effects, the PCE of Sn-Pb PSCs reaches 21.46% (1 sun, AM1.5), maintaining excellent stability under a nitrogen atmosphere. Hence, the buried interface approach exhibits the potential for achieving high-performance and stable Sn-Pb PSCs.

Herein we present a novel design of Y-series acceptors by strategically introducing designed terminal groups that modulate dipole moments and intramolecular charge transfer (ICT). By incorporating a methoxy group and a halogen atom at specific positions of the terminal groups results in asymmetric acceptors with attenuated ICT effects and broader band gaps. The optimized ternary devices exhibit a remarkable power conversion efficiency of 19.34 %.

Abstract

This study puts forth a novel terminal group design to develop medium-band gap Y-series acceptors beyond conventional side-chain engineering. We focused on the strategical integration of an electron-donating methoxy group and an electron-withdrawing halogen atom at benzene-fused terminal groups. This combination precisely modulated the dipole moment and electron density of terminal groups, effectively attenuating intramolecular charge transfer effect, and widening the band gap of acceptors. The incorporation of these terminal groups yielded two asymmetric acceptors, named BTP-2FClO and BTP-2FBrO, both of which exhibited open-circuit voltage (V _oc) as high as 0.96 V in binary devices, representing the highest V _OCs among the asymmetric Y-series small molecule acceptors. More importantly, both BTP-2FClO and BTP-2FBrO exhibit modest aggregation behaviors and molecular crystallinity, making them suitable as a third component to mitigate excess aggregation of the PM6 : BTP-eC9 blend and optimize the devices’ morphology. As a result, the optimized BTP-2FClO-based ternary organic solar cells (OSCs) achieved a remarkable power conversion efficiency (PCE) of 19.34 %, positioning it among the highest-performing OSCs. Our study highlights the molecular design importance on manipulating dipole moments and electron density in developing medium-band gap acceptors, and offers a highly efficient third component for high-performance ternary OSCs.

A direction modulation of intramolecular electric field (IEF) strategy is demonstrated to be a crucial factor to improve the charge transport capabilities of conjugated molecules. Furthermore, we obtain a set of empirical formulas to provide a potential approach to rapidly assess the hole transport properties based on molecular structure. Such a modulation results in a record performance of 23.41 % for perovskite solar cells based on phthalocyanine as dopant-free hole transport material. The greatly improved device stability is also obtained.

Abstract

Tuning the strength of intramolecular electric field (IEF) in conjugated molecules has emerged as an effective approach to boost charge transfer. While direction manipulation of IEF would be a potential way that is still unclear. Here, we leverage the control of peripheral substituents of conjugated phthalocyanines to chemically tune the spatial orientation of IEF. By analyzing the spatial swing of side chains using the Kolmogorov-Arnold representation and least squares algorithm, a comprehensive mathematical-physical model has been established. This model enables rapid evaluation of the IEF and maximum hole transport performance induced by spatial swings. The champion phthalocyanine as dopant-free hole transport material in perovskite solar cell realizes a record performance of 23.41 %. Greatly device stability is also exhibited. This work affords a new way to enhance hole transport capabilities of conjugated molecules by optimizing their IEF vector for photovoltaic devices.

Publication date: January 2025

Source: Journal of Energy Chemistry, Volume 100

Author(s): Guoqiang Ma, Qin Tan, Zhaoning Li, Jingwei Xiu, Jiafeng Wang, Tianle Cheng, Dong He, Qiang Sun, Xuhang Ma, Francesco Lamberti, Zhubing He

We propose a cation engineering approach to improve the optoelectronic properties of formamidine–cesium (FA-Cs) wide-bandgap (WBG) perovskites by incorporating methylamine (MA) as the third cation. MA can enhance the crystallinity, reduce microstrain, and improve the carrier lifetimes of perovskite films. Among the nine types of WBG perovskites, solar cells based on Cs_0.25MA_0.03FA_0.72PbI_2.73Br_0.27 perovskite demonstrate the highest efficiency and best stability.

Large voltage deficit and photoinduced halide segregation are the two primary challenges that hinder the advancement of wide-bandgap (WBG) (E _g ≥ 1.65 eV) perovskite solar cells (PSCs). Herein, a cation engineering approach to enhance the optoelectronic properties of formamidine–cesium (FA-Cs) WBG perovskites by incorporating methylamine (MA) as the third cation is presented. Three perovskite species with a bandgap of 1.68 eV, abbreviated as Cs_0.05, Cs_0.15, and Cs_0.25, are systematically studied by optimizing the MA content. The incorporation of MA is found to effectively enhance the crystallinity and improve the carrier lifetimes of the three perovskite species. Moreover, the microstrain in the FA-MA-Cs perovskite films is significantly reduced due to the buffer effect of MA between the size-mismatched FA and Cs, a benefit derived from the cascade cation design. The optimized compositions for the three species are Cs_0.05MA_0.2FA_0.75PbI_2.58Br_0.42, Cs_0.15MA_0.1FA_0.75PbI_2.68Br_0.32, and Cs_0.25MA_0.03FA_0.72PbI_2.73Br_0.27, respectively. Among these, Cs_0.25MA_0.03FA_0.72PbI_2.73Br_0.27 perovskite stands out due to its high crystallinity, low microstrain, and low trap density, giving rise to the highest efficiency of 20.64% with the lowest voltage loss. This perovskite also exhibits superior air, light, and thermal stability. These findings underscore the importance of rational cation design in achieving efficient and photostable WBG PSCs.

Aromatic D-A configured phthalocyanine achieves dual-site passivation of uncoordinated lead ions while effectively passivating shallow and deep-level defects on perovskite surfaces. Pc-BTBC demonstrate compatibility with various perovskite compositions, optimize PSCs achieved a PCE of 25.15% and reduce the V_OC deficit to 0.379 V, and the fabricated 4T-P/STSCs demonstrated an impressive PCE of 29.38%.

Abstract

The performance of perovskite solar cells (PSCs) is often constrained by significant open-circuit voltage (V_OC ) losses attributed to non-radiative recombination processes induced by detrimental trap states. Surface treatments using passivating ligands typically involve single active binding sites on perovskite, posing challenges for effective passivation. Here, an aromatic donor-acceptor (D-A) configured phthalocyanine treatment is proposed to aim at dual-site passivation of uncoordinated lead ions and effective mitigation of shallow and deep-level defects on the perovskite surface. The resulting benign p-type surface facilitates a more favorable energy level alignment and reduces energetic mismatches at the perovskite/Spiro-OMeTAD interface. Pc-BTBC, with its aromatic D-A configuration, demonstrated compatibility with various perovskite compositions. Optimized PSCs achieves a power conversion efficiency (PCE) of 25.15% and reduces the V_OC deficit to 0.379 V. Furthermore, encapsulated devices exhibited enhanced stability under damp-heat conditions (ISOS-D-2, 50% RH, 65°C) with a T₉₂ of 1000 h and maintained maximum power point tracking under continuous light in ambient air at 65°C (ISOS-L-2). Notably, fabricated wide-bandgap semitransparent PSCs (ST-PSCs) achieved a PCE of 20.29%, while four-terminal perovskite/silicon tandem solar cells (4T-P/STSCs) demonstrated an efficiency of 29.38%. This study provides insights into minimizing V_OC losses and represents significant progress toward commercializing perovskite photovoltaics.

Our study shows that the introduced EWMs can improve perovskite device performance by enhancing chemical passivation and interface dipole effect, as well as chemical binding to Spiro-OMeTAD. After optimization, devices modified with F4TCNQ achieved a remarkable 25.21 % efficiency and displayed long-term stability. Additionally, large-scale devices (14.0 cm²) using this approach achieved a high 21.4 % efficiency.

Abstract

Electron-withdrawing molecules (EWMs) have exhibited remarkable efficacy in boosting the performance of perovskite solar cells (PSCs). However, the underneath mechanisms governing their positive attributes remain inadequately understood. Herein, we conducted a comprehensive study on EWMs by comparing 2,2′-(2,5-cyclohexadiene-1,4-diylidene) bismalononitrile (TCNQ) and (2,3,5,6-tetrafluoro-2,5-cyclohexadiene-1,4-diylidene) dimalononitrile (F4TCNQ) employed at the perovskite/hole transport layer (HTL) interfaces. Our findings reveal that EWMs simultaneously enhance chemical passivation, interface dipole effect, and chemically binding of the perovskite to the HTL. Notably, F4TCNQ, with its superior electron-withdrawing properties, demonstrates a more pronounced impact. Consequently, PCSs modified with F4TCNQ achieved an impressive power conversion efficiency (PCE) of 25.21 %, while demonstrating excellent long-term stability. Moreover, the PCE of a larger-area perovskite module (14.0 cm²) based on F4TCNQ reached 21.41 %. This work illuminates the multifaceted mechanisms of EWMs at the interfaces in PSCs, delivering pivotal insights that pave the way for the sophisticated design and strategic application of EWMs, thereby propelling the advancement of perovskite photovoltaic technology.

A water-solution-processed hybrid electron transport layer (ETL) is developed, significantly enhancing both the efficiency and stability of inverted structure organic solar cells (OSCs). Notably, a record efficiency of 19.07% is achieved for single-junction inverted OSCs using this hybrid ETL.

Abstract

Achieving both high efficiency and stability in organic solar cells (OSCs) remains a significant challenge. Inverted structure OSCs, compared to those with a normal structure, show great potential for combining high efficiency with enhanced stability. However, despite their improved stability, the efficiencies of inverted OSCs still lag behind those of conventional structure OSCs, largely due to the performance of electron transport layers (ETLs). Herein, a water-soluble hybrid ETL is developed by modifying SnO₂ nanoparticles with an aqueous potassium carboxylate salt, PMA. This modification effectively passivates the oxygen vacancy defects in the SnO₂ nanoparticles and eliminates the light soaking issue observed in the control device. As a result, the PM6:Y6-based device shows an improvement in efficiency from 16.68% to 17.85% with PMA modification. Notably, an exceptional efficiency of 19.07% is achieved for the PM6:BTP-eC9-based device using this hybrid ETL, marking the highest efficiency reported to date for single-junction inverted OSCs. In addition, all tested OSCs with the hybrid ETL demonstrate superior stability under both thermal and light illumination at the maximum power point compared to the control devices. Furthermore, utilizing this water-processed hybrid ETL, a large-area module based on PM6:BO-4Cl is fabricated and shows an outstanding efficiency of 15.02%.

The bidirectional synergistic crystallization strategy can be realized by introducing guanidine chloride (GACl) at the buried interface between the perovskite film and TiO₂ electron transport layer. This strategy significantly improves the quality of the perovskite film, eradicates residual strain, and consequently enhances the efficiency and stability of the as-prepared perovskite solar cells.

Abstract

Crystalline quality is paramount for the performance and stability of perovskite films and devices. By regulating the nucleation and growth processes, it is possible to significantly enhance the crystalline quality. This work introduces a bidirectional synergistic crystallization strategy (BSC strategy) that synchronizes the crystallization kinetics across both the top and bottom surfaces of the perovskite film, thereby enhancing film quality and boosting the efficiency of perovskite solar cells (PSCs). Employing time-resolved optical characterization techniques, it is demonstrated that the BSC strategy effectively mitigates the dissolution–recrystallization cycle of the perovskite nuclei and grains during annealing, accelerates the evaporation of residual solvents at the bottom of the perovskite film, and suppresses void formation at the buried interface. Depth-resolved grazing-incidence wide-angle scattering analyses further confirm that the BSC strategy improves the crystalline quality of the perovskite film, promotes oriented growth, and minimizes internal residual strains caused by uneven growth dynamics. This approach results in a champion device efficiency of 24.98%, with the low voltage deficit of 360 mV. Moreover, device stability is markedly enhanced, after 1000 h of continuous light exposure, the efficiency remains over 91% of the initial value.

Two thiophene derivatives can interact with Sn²⁺ through ligand bonding and immobilize halide ions through hydrogen bonding. Due to the strong interactions, the defects are effectively passivated and the lattice is more stable. Consequently, the carrier diffusion length and the power conversion efficiency of the target device with α-TEACl are up to 1102.20 nm and 14.02%, respectively.

Abstract

Sn²⁺ oxidation and halide migration are recognized as the major constraints for high-performance tin halide perovskite solar cells (TPSCs), as they increase the defect state density and thus decrease the carrier lifetime and diffusion length. In this study, two chloride salts of thiophene derivatives are reported to interact with Sn²⁺ through ligand bonding and immobilize halide ions through hydrogen bonding. Due to the stronger interactions between 1-(2-thiophene)ethylamine hydrochloride (α-TEACl) and the perovskite components, better defect passivation is realized. In addition, thanks to the coordination ability, the lattice stability of tin perovskite is enhanced, and the photoluminescence carrier lifetime and carrier diffusion length are substantially extended from 4.51 ns and 180.78 nm to 23.17 ns, and 1102.20 nm, respectively, which are both among the highest reported values for tin halide perovskites. Consequently, the target device with α-TEACl achieved a power conversion efficiency (PCE) of up to 14.02%. At the same time, the α-TEACl device showed excellent long-term operational stability, retaining ≈92% of the initial efficiency after 2000 h aging in the N₂ atmosphere. This work provides a new perspective for regulating the defect passivation and ion migration in lead-free tin halide perovskites.

Publication date: 1 December 2024

Source: Nano Energy, Volume 131, Part A

Author(s): Xiaodong Si, Wendi Shi, Ruohan Wang, Wenkai Zhao, Zhaochen Suo, Zhen Fu, Guankui Long, Xiaotao Hao, Zhaoyang Yao, Xiangjian Wan, Chenxi Li, Yongsheng Chen

Introducing the first-ever perovskite solar cells (PSCs) on polycarbonate (PC) films via novel planarization, reducing surface roughness and boosting chemical and moisture resistance. Flexible devices deliver 13.0% efficiency, with satisfactory flexibility and stability in air. This innovation can enable future solar power integration in ID cards, smart packaging, and beyond, representing a significant step forward in smart photovoltaic technology.

Abstract

The market for polycarbonate (PC), a versatile material, is growing rapidly. Despite its widespread use in many applications, poor chemical resistance and roughness have hindered its adoption as a substrate in solar cell technologies. Here, the first-ever perovskite solar cell (PSC) is demonstrated on PC films. A solution-processed planarizing layer is developed using a commercial ambient-curable refractory resin through blade coating which decreased film roughness from 1.46 µm to 23 nm, lowered water vapor transmission rates (WVTR) by a half, and significantly improved solvent resistance enabling deposition of precursor inks. The PSCs are fabricated on the planarized PC substrate, with a customized ITO electrode with an average visible transparency of 78%, sheet resistance of 25 Ω/sq, and a safe bending radius of 20 mm. The power conversion efficiency (PCE) reached 13.0%. The unencapsulated PSCs retained 80% of initial PCE after 1776 h upon ISOS-D-1 shelf-life tests. These results open new pathways for integrating solar cells in many products made from PC materials, such as ID cards, smart cards, windows, skylights, buildings, and product packaging, as well as introducing a new solution for planarization and solvent barrier that can be used for other types of optoelectronic devices (LEDs, transistors, etc.) and substrates.

A family of fluorine terminated dual-site organic dipole molecules is investigated to engineer interfacial properties. Through the tunable interfacial field via tailored side-chain, a gradient energy level alignment with more favorable energetics is established, and the resulting N-i-P perovskite solar cell demonstrates a record high efficiency value of 25.47% together with enhanced long-term operational stability.

Abstract

The interfacial management in perovskite solar cells (PSCs), including mitigating the carrier transport barrier and suppressing non-radiative recombination, still remains a significant challenge for efficiency and stability enhancement. Herein, by screening a family of fluorine (F) terminated dual-site organic dipole molecules, the study aims to gain insight into the molecular dipole array toward tunable interfacial field. Both experimental and theoretical results reveal that these functional interfacial dipole molecules can effectively anchor on perovskite surface through Lewis acid-base interaction. In addition, the tailored side-chain with terminated F atoms allows for altering and constructing a well matched perovskite/Spiro-OMeTAD interfacial contact. As a result, the inserting dual-site organic dipole array effectively modulates the interface to deliver a gradient energy level alignment, facilitating carrier extraction and transport. The optimal dual-site dipole trifluoro-methanesulfonamide mediated N-i-P PSCs achieve the highest efficiency of 25.47%, together with enhanced operational stability under 1000 h of the simulated 1-sun illumination exposure. These findings are believed to provide insight into the design of dual-site molecular dipole with sufficient interfacial tunability for perovskite-based optoelectronic devices.

Structure-dependent effects of the four well-defined multidentate fullerenes on the device performance of tin-based perovskite solar cells are systemically investigated. Due to favorable energy level alignment and interface interactions, devices based on FM5 achieved a PCE of 15.05%, ranking among the top-performing tin-based devices.

Abstract

Improving the efficiency of tin-based perovskite solar cells (TPSCs) is significantly hindered by energy level mismatch and weak interactions at the interface between the tin-based perovskite and fullerene-based electron transport layers (ETLs). In this study, four well-defined multidentate fullerene molecules with 3, 4, 5, and 6 diethylmalonate groups, labeled as FM3, FM4, FM5, and FM6 are synthesized, and employed as interfacial layers in TPSCs. It is observed that increasing the number of functional groups in these fullerenes leads to shallower lowest unoccupied molecular orbital (LUMO) energy levels and enhance interfacial chemical interactions. Notably, FM5 exhibits a suitable energy level and robust interaction with the perovskite, effectively enhancing electron extraction and defect passivation. Additionally, the unique molecular structure of FM5 allows the exposed carbon cage to be tightly stacked with the upper fullerene cage after interaction with the perovskite, facilitating efficient charge transfer and protecting the perovskite from moisture and oxygen damage. As a result, the FM5-based device achieves a champion efficiency of 15.05%, significantly surpassing that of the PCBM-based (11.77%), FM3-based (13.54%), FM4-based (14.34%), and FM6-based (13.75%) devices. Moreover, the FM5-based unencapsulated device exhibits excellent stability, maintaining over 90% of its initial efficiency even after 300 h of air exposure.

Two isomer dimer acceptors were designed and synthesized, D-TPh and D-TN, which differ in the positional arrangement of their end capping groups. D-TPh exhibited enhanced planarity, elevated LUMO energy, more ordered stacking, and desirable phase separation. Consequently, the OSC device based on PM6 : D-TPh achieved a higher efficiency of 19.05 % and long-term stability.

Abstract

The strategy of isomerization is known for its simple yet effective role in optimizing molecular configuration and enhancing the power conversion efficiency (PCE) of organic solar cells (OSCs). However, the impact of isomerization on the design of dimer acceptors has been rarely investigated, and the relationship between the chemical structure and optoelectronic property remains unclear. In this study, we designed and synthesized two dimer acceptor isomers named D-TPh and D-TN, which differ in the positional arrangement of their end capping groups. Compared to D-TN, D-TPh exhibited enhanced backbone planarity, elevated lowest unoccupied molecular orbital energy level, and more ordered molecular stacking. Consequently, the OSC device based on PM6 : D-TPh achieved a PCE of 19.05 %, higher than that (PCE=18.42 %) of the device based on PM6 : D-TN. Large-area PM6 : D-TPh devices (1 cm²) yielded a PCE of 18.00 %. More importantly, the extrapolated T ₈₀ lifetime of the PM6 : D-TPh device is over 2800 h with MPP tracking under continuous one-sun illumination. These results suggest that isomerization strategy is an effective way to optimize the molecular configuration of dimer acceptors for the fabrication of high-efficiency and stable OSCs.

Nature, Published online: 05 September 2024; doi:10.1038/s41586-024-07997-7