Chen Weijie

Publication date: 17 January 2024

Source: Joule, Volume 8, Issue 1

Author(s): Zhi-Wen Gao, Yong Wang, Xiwen Chen, Zhengyan Jiang, Minchao Qin, Weihua Ning, Bihua Hu, Xinhui Lu, Wan-Jian Yin, Deren Yang, Baomin Xu, Wallace C.H. Choy

In this work, ortho-, meta-, and para-isomers of phenylenediamine (PDA) spacer are introduced. Compared with p-PDA and m-PDA, o-PDA not only reduces the exciton binding energy and facilitates the effective separation of excitons, but also weakens the quantum confinement effect and realizes effective carrier transport. Importantly, 2D DJ (o-PDA)FA₃Sn₄I₁₃ solar cell shows a record power conversion efficiency of 7.18% and enhanced stability.

Abstract

2D Dion–Jacobson (DJ) tin halide perovskite shows impressive stability by introducing diamine organic spacer. However, due to the dielectric confinement and uncontrollable crystallization process, 2D DJ perovskite usually exhibits large exciton binding energy and poor film quality, resulting in unfavorable charge dissociation, carrier transport and device performance. Here, the ortho-, meta-, and para-isomers of phenylenediamine (PDA) are designed for 2D DJ tin halide perovskites. Theoretical simulation and experimental characterizations demonstrate that compared with p-PDA and m-PDA, o-PDA shows larger dipole moment, which further reduces the exciton binding energy for the 2D perovskites. Besides, there is a strong hydrogen bond interaction between o-PDA cation and inorganic octahedron, which not only improves the structural stability, but also induces larger aggregates in the precursor to form dense and uniform high-quality films, and strengthens the antioxidant barrier. More interestingly, femtosecond transient absorption further proves that o-PDA organic spacers can reduce unfavorable small n-phases, resulting in sufficient and effective charge transfer between different n-value. As a result, the 2D DJ (o-PDA)FA₃Sn₄I₁₃ solar cells achieve a record power conversion efficiency of 7.18%. The study furnishes an effective method to optimize the carrier transport and device performance by tailoring the chemical structure of organic spacers.

Herein, sodium phytate is introduced to stabilize the tin oxide (SnO₂) dispersion due to its strong interaction with SnO₂ nanocrystal, thus suppressing the formation of agglomerations and facilitating the homogeneous deposition of printable SnO₂ electron transport layers for perovskite solar cells (PVSCs). These also ensure controlled nucleation crystallization in perovskite precursor, effectively improving the photovoltaic performance, stability and all-weather printing reproducibility of the final PVSCs.

Abstract

Substandard printing quality of electron transport layers (ETLs) always leads to non-ideal nucleation crystallization and bottom interface contact of the perovskite, followed by the formation of poor-quality perovskite films with severe heterogeneity, which is the major source of non-radiative recombination loss and environmental sensitivity of perovskite solar cells (PVSCs). These often result in serious photovoltaic performance loss, significant instability, and negative fabrication reproducibility. Herein, sodium phytate is proposed as a chelating agent for passivating the tin oxide (SnO₂) ETLs to enable the stabilization of SnO₂ nanoparticles and facilitate the printing of pinhole-free films, thereby realizing the controlled nucleation crystallization in perovskite precursor. Thus, the printed PVSCs exhibit a champion power conversion efficiency up to 23.77% with negligible hysteresis effect. The unencapsulated devices demonstrate outstanding long-term stability, which maintains over 80% of their initial efficiency under exposure to atmospheric environment (50% relative humidity) for 1500 hours, and a consistent and centralized distribution of efficiencies across all seasons, indicating their good reproducibility in diverse climatic atmospheres.

This study examines the extensive metal halide perovskite device data compiled in the Perovskite Database, comprising more than 40,000 devices. The collective efforts of over a decade of perovskite research enable the identification of overarching trends in higher bandgap devices. Increasing efficiency loss with bandgap is attributed to mismatched transport materials, compositional inhomogeneity, and suboptimal optoelectronic absorber quality.

Abstract

Metal halide perovskites (MHPs) have become a widely studied class of semiconductors for various optoelectronic devices. The possibility to tune their bandgap (E _g) over a broad spectral range from 1.2 eV to 3 eV by compositional engineering makes them particularly attractive for light emitting devices and multi-junction solar cells. In this metadata study, data from Peer-reviewed publications available in the Perovskite Database (www.perovskitedatabase.com) is used to evaluate the current state of E _g tuning in wide E _g MHP semiconductors. Recent literature on wide E _g MHP semiconductors is examined and the data is extracted and uploaded onto the Perovskite Database. Beyond describing recent highlights and scientific breakthroughs, general trends are drawn from 45,000 individual experimental datasets of MHP solar cell devices. The historical evolution of MHP solar cells is recapitulated, and general conclusions are drawn about the current limits of device performance. Three dominant causes are identified and discussed for the degradation of performance relative to the Shockley-Queisser (SQ) model's theoretical limit for single-junction solar cells: 1) energetically mismatched selective transport materials for wide Eg MHPs, 2) lower optoelectronic quality of wide E _g MHP absorbers, and 3) dynamically evolving compositional heterogeneity due to light-induced phase segregation phenomena.

is-OPVs with a record efficiency of 16.23%, excellent flexibility and commendable stretchability are achieved by delicate optimizations from material to device, especially the elastic polymer SEPS-containing active layer and conductive polymer/metal (M-PH1000@Ag) composite electrode.

Abstract

The development of intrinsically stretchable organic photovoltaics (is-OPVs) with a high efficiency is of significance for practical application. However, their efficiencies lag far behind those of rigid or even flexible counterparts. To address this issue, an advanced top-illuminated OPV is designed and fabricated, which is intrinsically stretchable and has a high performance, through systematic optimizations from material to device. First, the stretchability of the active layer is largely increased by adding a low-elastic-modulus elastomer of styrene-ethylene-propylene-styrene tri-block copolymer (SEPS). Second, the stretchability and conductivity of the opaque electrode are enhanced by a conductive polymer/metal (denoted as M-PH1000@Ag) composite electrode strategy. Third, the optical and electrical properties of a sliver nanowire transparent electrode are improved by a solvent vapor annealing strategy. High-performance is-OPVs are successfully fabricated with a top-illuminated structure, which provides a record-high efficiency of 16.23%. Additionally, by incorporating 5–10% elastomer, a balance between the efficiency and stretchability of the is-OPVs is achieved. This study provides valuable insights into material and device optimizations for high-efficiency is-OPVs, with a low-cost production and excellent stretchability, which indicates a high potential for future applications of OPVs.

Publication date: 17 January 2024

Source: Joule, Volume 8, Issue 1

Author(s): Clara A. Aranda, Agustin O. Alvarez, Vladimir S. Chivrony, Chittaranjan Das, Monika Rai, Michael Saliba

Herein, 2-hydroxybenzophenone is introduced into the precursor to passivate the defects and absorb ultraviolet in the perovskite film. Meanwhile, ZnO mesoporous layer is developed as the electron transport layer to improve the effective electron extraction/transport. The power conversion efficiency of the constructed device is up to 16.39%, and the long-term environmental and ultraviolet irradiated stability is also significantly enhanced.

Although the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is 26.1%, their stability is still a roadblock for large-scale commercialization. In the initial density-functional theory research, it is shown that the most damaging type of defect that destroys device performance is undercoordinated Pb²⁺ on the surface of the perovskite thin film. An ultraviolet-absorbent material, 2-hydroxybenzophenone (HBP), is utilized to specifically passivate this type of defect. In theoretical studies, it is shown that it effectively binds to the undercoordinated Pb²⁺ via its –C═O group. It also passivates I⁻-related defects by forming a hydrogen bond using its –OH group, resulting in decreased trap density and hence prolonged carrier lifetime. The HBP can absorb ultraviolet irradiation, leading to much-reduced UV degradation; its hydrophobic benzene rings protect the perovskite from moisture permeation. As a result, the constructed device reaches a high PCE of 16.39% with superior stability. The bare device maintains 80.4% of its initial PCE after exposure to ambient air for 792 h. In comparison, the control device without HBP retains only 63.2% of its initial efficiency. Under UV irradiation (80 mW cm⁻², 365 nm) for 13 h, the former retains 77.9% of its initial PCE while the control device lost 52% of its initial value.

The performance of perovskite solar cells (PSCs) is enhanced through the utilization of sputtered NiO _x as a hole-transport layer. The inverted PSCs exhibit a remarkable power conversion efficiency of 20.54%, marking the highest reported performance among sputtered NiO _x -based PSCs. In the results, the adaptability of NiO _x is underscored to diverse perovskite compositions and structural variations, while maintaining stability.

Perovskite solar cells (PSCs) are now approaching their theoretical limits and the optimization of the auxiliary layers is crucial for fully exploiting the potential of perovskite materials. In this study, NiO _x as a hole-transport layer (HTL) for inverted p–i–n PSCs is focused on. Sputtered NiO _x is an attractive p-type HTL owing to its facile processing, wide energy bandgap that prevents electron transfer, high transparency, stability, and effective hole extraction. Despite substantial research on sputtered NiO _x , the relationship between the carrier concentration and work function is still unclear. In this study, the use of sputtered NiO _x as a widely compatible HTL and the effect of its thickness on PSC device performance are investigated. Inverted PSCs with the optimal 10 nm thick NiO _x achieve a remarkable power conversion efficiency of 20.54%, which is the highest reported to date for sputtered NiO _x -based PSCs. Furthermore, PSCs with various NiO _x thicknesses demonstrate similar performances, demonstrating the excellent versatility of NiO _x for use with different perovskite absorbers. The devices exhibit excellent thermal and photostability, retaining 97% of their initial power conversion efficiency at 65 °C and 1 sun illumination for 350 h. Sputtered NiO _x HTLs have great potential for use with diverse perovskite compositions and PSC structures.

An effective strategy is proposed for managing defects at the perovskite interface, that is, using mixed-salt trimethylsulfoxonium iodide (TMSI) to improve the defect formation energy, fill the iodide vacancies, and inhibit the generation of Pb⁰ defects.

Abstract

Iodine vacancies and uncoordinated Pb⁰ defects existing at the perovskite surface have been widely demonstrated to induce deep-level defects, which can greatly limit improvement of the efficiency and stability of perovskite solar cells (PSCs). In this work, a novel strategy is proposed for functionalizing perovskite surface by using trimethylsulfoxonium iodide (TMSI), which can enhance the defect formation energy and inhibit Pb⁰ defects. Meanwhile, TMSI modification also can fill the iodine vacancies of perovskite surface-terminating ends. Consequently, the optimized device shows the improved charge dynamics and the reduced energy losses, achieving a champion efficiency of up to 24.03% along with excellent air-storage and thermal stabilities. This work offers guidelines for more efficient and stable PSCs based on the management of interface defects.

This review summarizes the origin of perovskite solar cell (PSC) degradation and the recent development of in situ cross-linking strategy in PSCs to enhance the moisture, thermal, illumination, and tensile stress resistance properties of perovskite. Moreover, the current challenges to further develop the in situ cross-linking strategy to enable high stability and efficiency of PSCs are thoroughly discussed.

Abstract

The perovskite solar cells (PSCs) have achieved great success in power conversion efficiency due to their excellent optoelectrical properties of perovskite. However, the instability of PSCs severely impedes their commercialization. Recently, in situ cross-linking strategy has been proposed to mitigate stability issues of PSCs, enabling highly efficient and stable PSCs. Here, the critical factors that lead to the degradation of PSCs are first outlined. Then, a comprehensive review of in situ cross-linking strategy in perovskite to enhance the moisture, thermal, illumination, and bending stress resistance properties of PSCs is presented. Furthermore, the detailed mechanism underlying these advantageous effects is discussed pertaining to crystallization regulation, immobilization of ions, water resistance, and release of unfavorable stress. Finally, the current challenges and further development trends of in situ cross-linking strategy in PSCs and extension to other optoelectronic devices are prospected.

CsPbI_2.77I_0.23 slot-die inks are developed via the colloidal engineering of scalable large-area perovskite solar cells. Eco-friendly solvents such as dimethyl sulfoxide, acetonitrile, and 2-methoxyethanol are used. Film growth is controlled by varying the solvent ratio. The cells based on films prepared by slot-die coating exhibit an efficiency of 19.05%.

Abstract

The performance of large-area perovskite solar cells (PSCs) has been assessed for typical compositions, such as methylammonium lead iodide (MAPbI₃), using a blade coater, slot-die coater, solution shearing, ink-jet printing, and thermal evaporation. However, the fabrication of large-area all-inorganic perovskite films is not well developed. This study develops, for the first time, an eco-friendly solvent engineered all-inorganic perovskite ink of dimethyl sulfoxide (DMSO) as a main solvent with the addition of acetonitrile (ACN), 2-methoxyethanol (2-ME), or a mixture of ACN and 2-ME to fabricate large-area CsPbI_2.77Br_0.23 films with slot-die coater at low temperatures (40–50 °C). The perovskite phase, morphology, defect density, and optoelectrical properties of prepared with different solvent ratios are thoroughly examined and they are correlated with their respective colloidal size distribution and solar cell performance. The optimized slot-die-coated CsPbI_2.77Br_0.23 perovskite film, which is prepared from the eco-friendly binary solvents dimethyl sulfoxide:acetonitrile (0.8:0.2 v/v), demonstrates an impressive power conversion efficiency (PCE) of 19.05%. Moreover, the device maintains ≈91% of its original PCE after 1 month at 20% relative humidity in the dark. It is believed that this study will accelerate the reliable manufacturing of perovskite devices.

By introducing the polydopamine into the SnO₂ electron transport layers (ETLs) as “depletion intermediary,” the inherent brittleness of SnO₂ and the interfacial mismatches between SnO₂ ETLs and perovskite layers are significantly passivated. As a result, the power conversion efficiency of the flexible perovskite solar cells reaches 21.04%, and 87% of its initial efficiency has been retained after 3000 bending cycles.

SnO₂ has been a widely used electron transport layer, due to its high electron mobility and stable chemical properties in n–i–p type perovskite solar cells (PSCs). However, the interfacial mismatch, especially on the residual strain and the different mechanical properties between SnO₂ and perovskite films, leads to an obvious decrease in power conversion efficiency (PCE) and flexibility in the SnO₂-based PSCs. This limitation has severely hindered the large-scale implementation of flexible PSCs. Herein, polydopamine is introduced in SnO₂ as “depletion intermediary”, which significantly improves the interfacial contact and mitigates the inherent brittleness of SnO₂ film. The obtained PSCs have achieved a PCE of 22.70% and 21.04% based on the rigid and flexible devices, respectively. Most importantly, the flexibility has been largely improved, that after 3000 bending cycles with a 5 mm bending radius, approximately 87% of its original efficiency has been retained.

Nature Materials, Published online: 11 December 2023; doi:10.1038/s41563-023-01724-9

The poor quality of the tin-based perovskite surface resulting from Sn²⁺ oxidation and uncontrollable crystallization can greatly affect the device performance and stability. Herein, a novel biguanide derivative of PZBGACl that integrates different types of N-related groups as a perovskite surface passivator is used to fabricate Sn-Pb perovskite solar cells, and achieve an encouraging power conversion efficiency of 22.0% with good stability.

Abstract

Tin-lead (Sn-Pb) mixed perovskites is beneficial to a single-junction or all-perovskite tandem device. However, the poor quality of the perovskite surface resulting from Sn²⁺ oxidation and uncontrollable crystallization degrades device performance and stability. Herein, based on interface engineering, a novel biguanide derivative of PZBGACl is employed that integrates different types of N-related groups to reconstruct the surface/grain boundaries of Sn-Pb perovskite. Combined with the microcorrosion effect of isopropanol solvent, PZBGACl can induce surface recrystallization of perovskite, and passivate various types of defects via hydrogen bond or Lewis acid-base interaction, leading to an excellent perovskite film with reduced stress, larger grain size, and more n-type surface. As a result, the obtained Sn-Pb solar cell achieves a power conversion efficiency of 22.0%, and exhibits excellent N₂ storage/operation stability.

A fused naphthodithiophene diimide (NDTI) derivative is first used as cathode interlayer materials (CIMs) in organic solar cells, namely NDTI1. NDTI1 presents a strong self-doping effect, high electron mobility, and exceptional film-formation. The NDTI1-based OSCs achieve a power conversion efficiency (PCE) of 19.01% employing the PM6:L8-BO blend, which is attributed to improve charge transport and extraction, and suppressive charge recombination.

Abstract

A fused naphthodithiophene diimide (NDTI) derivative is first used as cathode interlayer materials (CIMs) in organic solar cells, by introducing two dimethylamine-functionalized fluorenes on both sides, namely NDTI1. Meanwhile, two non-fused naphthalene diimide (NDI) derivatives are synthesized as the control CIMs to validate the design strategy of fused NDI. All three CIMs show high thermal stability, robust adhesion, and strong electrode modification capability. Compared with two NDI-based materials, NDTI1 possesses excellent film-forming capacity and strong crystallinity, simultaneously. Besides, NDTI1 presents a strong self-doping effect and distinct intermolecular interaction with non-fullerene acceptors. As expected, the NDTI1-based OSCs achieve a power conversion efficiency (PCE) of 18.02% using the PM6:Y6 active layer and a champion PCE of 19.01% employing the active layer PM6:L8-BO, which is attributed to improve charge transport and extraction, and suppressive charge recombination. More importantly, NDTI1 retains 91% of the optimal PCE when the film thickness increases from 7 to 20 nm. Furthermore, NDTI1 also exhibits satisfactory universality for different active layer materials and excellent device stability.

The semitransparent perovskite solar cells (PSCs) modified with co-additives of KPF6 and CH3NH3Cl (MACl) are explored for MXene-interconnected tandem solar cells. The enhanced interfacial carrier transportation, with minimal influence on light transmission, imparted by the MXene flakes allowed the tandem solar cells to achieve an appealing efficiency of 30.26% and a certified value of 30.18% under reverse scan (RS).

Abstract

Two-terminal, mechanically-stacked perovskite/silicon tandem solar cells offer a feasible way to achieve power conversion efficiencies (PCEs) of over 35%, provided that the state-of-the-art industrial silicon solar cells and perovskite solar cells (PSCs) are fully compatible with one another. Herein, two-terminal, mechanically-stacked perovskite/silicon tandem solar cells are developed by mechanically interconnecting semitransparent PSCs and TOPCon solar cells with a MXene interlayer. The semitransparent PSCs are made from wide-bandgap perovskite Cs_0.15FA_0.65MA_0.20Pb(I_0.80Br_0.20)₃ films. Furthermore, the co-additives KPF₆ and CH₃NH₃Cl(MACl) are employed to reduce grain boundaries and intragranular defects in the perovskite, boosting the PCE of the semitransparent PSCs to a record-high value of 20.96% under reverse scan (RS) through a reduction in non-radiative recombination probability. These optimized semitransparent PSCs are then employed in MXene-interconnected two-terminal, mechanically-stacked tandem solar cells. The enhanced interfacial carrier transportation, with minimal influence on light transmission, imparted by the MXene flakes allows the tandem solar cells to achieve a stabilized PCE of 29.65%. The tandem cells also exhibit acceptable operational stability and are able to retain ≈93% and 92% of their initial PCEs after 120 min of continuous illumination or storage in ambient air for 1000 h, respectively.

This work reports a synergistic strategy of defect healing and device encapsulation for perovskite solar cells via the structure regulation of telechelic silicone polymer (PDMA). PDMA as an additive achieves defect healing, and cross-linked PDMA as an encapsulant achieves non-destructive encapsulation and delays the decomposition of perovskite. The resulting PSCs yield excellent operational stability and damp heat stability with high efficiency.

Abstract

Polymers play a crucial role in promoting the progress of high-performance inverted perovskite solar cells (PSCs). However, few polymers have simultaneously achieved defect passivation and device encapsulation in PSCs. Herein, a telechelic silicone polymer (poly(dimethylsiloxane-co-methylsiloxane acrylate) [PDMA]) is introduced, which possesses crosslinking capability to enable structure regulation through a condensation reaction. By leveraging the advantages of the polymers before and after crosslinking, a synergistic strategy of defect healing and device encapsulation for PSCs is developed via the application of the targeted polymer. PDMA as additives anchors tightly at the grain boundaries (GBs) and bridges the perovskite grains, achieving defect passivation and GBs crosslinking, increasing the efficiency of inverted PSCs from 22.32% to 24.41%. Crosslinked PDMA (CPDMA) is used as an encapsulant to encapsulate the entire device, enabling non-destructive encapsulation at room temperature and inhibiting perovskite degradation under photothermal aging. Remarkably, the PDMA-modified device with CPDMA encapsulation maintains 98% of its initial efficiency after 1200 h under continuous illumination at 55 ± 5 °C and retains 95% of its original efficiency after 1000 h of damp heat testing, meeting one of the IEC61215:2016 standards.

Sn composition-engineered indium tin oxide (CE-ITO) with superior performance over commercial ITO (C-ITO) is developed for highly efficient and stable perovskite solar cells (PSCs) using a magnetron co-sputtering process. By introducing the CE-ITO substrate into the mesoporous normal-type PSC with the TiO₂ electron transport layer, the device exhibits higher efficiency (23.35%) and improved stability than C-ITO substrate.

Abstract

To overcome the Shockley–Queisser limit, studies have focused on improving the efficiency of perovskite solar cells (PSCs) through several optimization and tandem-structure design strategies. Furthermore, the significance of emerging transparent front electrodes (TFEs), which exert a direct and substantial influence on the performance of PSCs, is on the rise. Therefore, further research must be conducted to validate these effects in improving the existing performance of PSCs. Thus, this study developed a composition-engineered indium tin oxide (CE-ITO) TFE that outperforms commercial ITO (C-ITO; 10 at.% Sn doped ITO) for efficient and stable PSCs. The CE-ITO electrode (7.50 at.% Sn doped ITO) has a large columnar structure and good thermal stability, which are ideal for high-performance PSCs. Compared to C-ITO, CE-ITO has a smoother surface, higher conductivity, lower resistivity, and improved optical transmittance in the active layer. These contribute to the larger perovskite active- and electron-transport layers, less active-layer degradation, and lower shunt resistance. The various merits of CE-ITO enable high-performance PSCs with a maximum power conversion efficiency of 23.35% and long-term stability by simply substituting C-ITO with optimal CE-ITO.