JIALINGBO

By regulating the electronic structure with ThFABr, an ultralong carrier lifetime exceeding 20 µs and carrier diffusion lengths longer than 6.5 µm is achieved in 2D/3D polycrystalline perovskite films. These excellent properties enable the ThFA-based devices yielding a champion efficiency of 24.69% and a high V _OC of 1.21 V, coupled with significantly improved operational stability.

Abstract

The carrier lifetime is one of the key parameters for perovskite solar cells (PSCs). However, it is still a great challenge to achieve long carrier lifetimes in perovskite films that are comparable with perovskite crystals owning to the large trap density resulting from the unavoidable defects in grain boundaries and surfaces. Here, by regulating the electronic structure with the developed 2-thiopheneformamidinium bromide (ThFABr) combined with the unique film structure of 2D perovskite layer caped 2D/3D polycrystalline perovskite film, an ultralong carrier lifetime exceeding 20 µs and carrier diffusion lengths longer than 6.5 µm are achieved. These excellent properties enable the ThFA-based devices to yield a champion efficiency of 24.69% with a minimum V _OC loss of 0.33 V. The unencapsulated device retains ≈95% of its initial efficiency after 1180 h by max power point (MPP) tracking under continuous light illumination. This work provides important implications for structured 2D/(2D/3D) perovskite films combined with unique FA-based spacers to achieve ultralong carrier lifetime for high-performance PSCs and other optoelectronic applications.

A room-temperature stable perovskite intermediate is constructed with a dual-component volatile solvent. By suppressing the nucleation rate in volatile precursor, this strategy provides a controllable grain growth rate and wide processing window in scalable film deposition without post-treatments.

Abstract

The unprecedented development of perovskite solar cells (PSCs) makes them one of the most promising candidates for terawatt-scale green energy production with low cost. However, the high boiling point solvents during the solution-processed film deposition cause anisotropic crystal growth and toxic solvent vapor during high-throughput manufacturing. Here, a dual-component green solvent consisting of isopropyl acetate and acetonitrile is proposed to form a volatile perovskite precursor, which can realize the high-quality perovskite thin film deposition by intermediate phase regulation. A room-temperature stable perovskite intermediate phase is constructed with the engagement of isopropyl acetate as co-solvent, which suppresses the exploding nucleation rate in volatile perovskite precursor, providing a fine grain growth rate and wide processing window in scalable film deposition. The corresponding PSCs fabricated by blade coating without anti-solvents or gas quenching achieve power conversion efficiency (PCE) of 16.37 % and 15.29 % for the areas of 14.08 cm² and 37.83 cm², respectively.

A small molecule of calix[4]pyrrole (C[4]P) with unique anion-bonding capability is demonstrated to enhance the stability of metal halide perovskites by immobilization of the surface halide. It largely suppresses the halide-diffusion induced electrode corrosion, enabling formamidinium–cesium-based inverted perovskite solar cells (efficiency over 23%) with operational and thermal lifetimes over 2000 h.

Abstract

Halide diffusion across the charge-transporting layer followed by a reaction with metal electrode represents a critical factor limiting the long-term stability of perovskite solar cells (PSCs). In this work, a supramolecular strategy with surface anion complexation is reported for enhancing the light and thermal stability of perovskite films, as well as devices. Calix[4]pyrrole (C[4]P) is demonstrated as a unique anion-binding agent for stabilizing the structure of perovskite by anchoring surface halides, which increases the activation energy for halide migration, thus effectively suppressing the halide–metal electrode reactions. The C[4]P-stabilized perovskite films preserve their initial morphology after ageing at 85 °C or under 1 sun illumination in humid air over 50 h, significantly outperforming the control samples. This strategy radically tackles the halide outward-diffusion issue without sacrificing charge extraction. Inverted-structured PSCs based on C[4]P modified formamidinium–cesium perovskite exhibit a champion power conversion efficiency of over 23%. The lifespans of unsealed PSCs are unprecedentedly prolonged from dozens of hours to over 2000 h under operation (ISOS-L-1) and 85 °C ageing (ISOS-D-2). When subjected to a harsher protocol of ISOS-L-2 with both light and thermal stresses, the C[4]P-based PSCs maintain 87% of original efficiency after ageing for 500 h.

Present work demonstrates an efficient strategy of the particle boundaries (PBs) embedding of multifunctional p-type semiconducting CdTe nanocrystals for inhibited carrier losses at PBs, which can serve as efficient PBs mediator for boosting the electrons mobility of TiO₂ ETL by maximally three orders of magnitude and consequently result in a new benchmark PCE over 25% in planar PSCs.

Abstract

Electron transport layers (ETLs) with pronounced electron conducting capability are essential for high performance planar perovskite photovoltaics, with the great challenge being that the most widely used metal oxide ETLs unfortunately have intrinsically low carrier mobility. Herein is demonstrated that by simply addressing the carrier loss at particle boundaries of TiO₂ ETLs, through embedding in ETL p–n heterointerfaces, the electron mobility of the ETLs can be boosted by three orders of magnitude. Such embedding is encouragingly favorable for both inhibiting the formation of rutile phase TiO₂ in ETL, and initiating the growth of high-quality perovskite films with less defect states. By virtue of these merits, creation of formamidinium lead iodide perovskite solar cells (PSCs) with a champion efficiency of 25.05% is achieved, setting a new benchmark for planar PSCs employing TiO₂ ETLs. Unencapsulated PSCs deliver much-improved environmental stability, i.e., more than 80% of their initial efficiency after 9000 h of air storage under RH of 40%, and over 90% of their initial efficiency at maximum power point under continuous illumination for 500 h. Further work exploring other p-type nanocrystals for embedding warrants the proposed strategy as a universal alternative for addressing the low-carrier mobility of metal oxide based ETLs.

Using 4-tert-Butyl-1-(ethoxycarbonyl- methoxy) thiacalix[4]arene (tBuTCA) to complex with the cations and out-of-cage (Lead(II) iodide) PbI₂ so that to compensate electrons for iodine vacancy defect. The negative charge compensation for iodine vacancy can hinder the formation of Pb-Pb dimer.

Abstract

Although there is extensive attention to the eminent perovskite solar cells, the deep-level defects such as Pb-Pb dimers in the solution-processed polycrystalline perovskites inevitably result in photovoltaic output losses and subsequent degradation. Recently, it is reported that an electron-donating group can passivate Pb dimer defects efficiently. However, the mechanism for the causation of metallic lead (Pb⁰) from the iodide vacancy (V_I) is unclear. Herein, a chain reaction mechanism is proposed for the possible transformation process from V_I to Pb⁰ with the Pb dimer intermediates. In this regard, a host-guest strategy is adopted by using 4-tert-Butyl-1-(ethoxycarbonyl- methoxy) thiacalix[4]arene (tBuTCA) to complex with the cations and out-of-cage (Lead(II) iodide) PbI₂. Moreover, a host-guest complexation can be formed due to the Pb²⁺-π interactions. Continuously, the negative charge compensation for iodine vacancy can hinder the formation of Pb-Pb dimer, thus significantly suppressing non-radiative recombination. Consequently, the resulting solar cells show more than 24% power conversion efficiencies and maintain over 96% of their initial performance without encapsulation for 486 h under an ambient environment. This work highlights the significance of supramolecular engineering in constructing a high-quality perovskite for efficient and stable perovskite solar cells.

The study discusses the development of stable, efficient, and scalable wide-bandgap perovskite solar cells (WBG-PSCs) using the hybrid evaporation-solution method (HESM), which co-evaporates PbI₂/CsBr layer and coats organic-halide solutions in a green solvent. The study achieves efficiencies of 21.06% in cells and 19.83% in mini-modules. The study concludes that HESM is a promising method for developing stable and high-performance WBG-PSCs .

Abstract

Wide-bandgap perovskite solar cells (WBG-PSCs), when partnered with Si bottom cells in tandem configuration, can provide efficiencies up to 44%; yet, the development of stable, efficient, and scalable WBG-PSCs is required. Here, the utility of the hybrid evaporation-solution method (HESM) is investigated to meet these demanding requirements via its unique advantages including ease of control and reproducibility. A PbI₂/CsBr layer is co-evaporated followed by coating of organic-halide solutions in a green solvent. Bandgaps between 1.55–1.67 eV are systematically screened by varying CsBr and MABr content. Champion efficiencies of 21.06% and 20.35% in cells and 19.83% and 18.73% in mini-modules (16 cm²) for perovskites with 1.64 and 1.67 eV bandgaps are achieved, respectively. Additionally, 18.51%-efficient semi-transparent WBG-PSCs are implemented in 4T perovskite/bifacial silicon configuration, reaching a projected power output of 30.61 mW cm⁻² based on PD IEC TS 60904-1-2 (BiFi200) protocol. Despite similar bandgaps achieved by incorporating Br via MABr solution and/or CsBr evaporation, PSCs having a perovskite layer without MABr addition show significantly higher thermal and moisture stability. This study proves scalable, high-performance, and stable WBG-PSCs are enabled by HESM, hence their use in tandems and in emerging applications such as indoor photovoltaics are now within reach.

The impact of the amorphous–crystalline (a–c) interface on the blocking performance of ZrN _x barrier films is investigated and the interface density is quantified for proving the interdiffusion channels by pattern recognition technology. The underlying mechanisms of a–c interfaces for blocking effects are further revealed in thermodynamic and kinetics properties, constructing stable inverted perovskite solar cells with amorphous ZrN _x barriers.

Abstract

It is challenging to achieve long-term stability of perovskite solar cells due to the corrosion and diffusion of metal electrodes. Integration of compact barriers into devices has been recognized as an effective strategy to protect the perovskite absorber and electrode. However, the difficulty is to construct a thin layer of a few nanometers that can delay ion migration and impede chemical reactions simultaneously, in which the delicate microstructure design of a stable material plays an important role. Herein, ZrN _x barrier films with high amorphization are introduced in p–i–n perovskite solar cells. To quantify the amorphous–crystalline (a–c) density, pattern recognition techniques are employed. It is found the decreasing a–c interface in an amorphous film leads to dense atom arrangement and uniform distribution of chemical potential, which retards the interdiffusion at the interface between ions and metal atoms and protect the electrodes from corrosion. The resultant solar cells exhibit improved operational stability, which retains 88% of initial efficiency after continuous maximum power point tracking under 1-Sun illumination at room temperature (25 °C) for 1500 h.

Perovskite solar cells (PVSCs) are a promising alternative to traditional silicon-based solar cells because of their high power-conversion efficiency and low cost. However, one of the major challenges in their development has been achieving long-term stability. Recently, a research team made a breakthrough by developing an innovative multifunctional and non-volatile additive which can improve the efficiency and stability of perovskite solar cells by modulating perovskite film growth. This simple and effective strategy has great potential for facilitating the commercialization of PVSCs.

The researchers introduce protic amine carboxylic acid ion liquids (PACA-ILs) into the perovskite precursor to regulate the phase transition and crystal growth processes. Preferentially oriented perovskite grains can be obtained by inhibiting the formation of MA₂Pb₃I₈·2DMSO phases. The optimized devices show high efficiency over 24% on small-area for all ILs and 21.26% on large-area module for methylammonium butyrate ILs.

Abstract

The α-phase formamidinium lead tri-iodide (α-FAPbI₃) has become the most promising photovoltaic absorber for perovskite solar cells (PSCs) due to its outstanding semiconductor properties and astonishing high efficiency. However, the incomplete crystallization and phase transition of α-FAPbI₃ substantially undermine the performance and stability of PSCs. In this work, a series of the protic amine carboxylic acid ion liquids are introduced as the precursor additives to efficiently regulate the crystal growth and phase transition processes of α-FAPbI₃. The MA₂Pb₃I₈·2DMSO phase is inhibited in annealing process, which remarkably optimizes the phase transition process of α-FAPbI₃. It is noted that the functional groups of carboxyl and ammonium passivate the undercoordinated lead ions, halide vacancies, and organic vacancies, eliminating the deleterious nonradiative recombination. Consequently, the small-area devices incorporated with 2% methylammonium butyrate (MAB) and 1.5% n-butylammonium formate (BAFa) in perovskite show champion efficiencies of 25.10% and 24.52%, respectively. Furthermore, the large-area modules (5 cm × 5 cm) achieve PCEs of 21.26% and 19.27% for MAB and BAFa additives, indicating the great potential for commercializing large-area PSCs.

This work demonstrates that the trap states induced by surface iodine vacancies significantly contribute to the generation-recombination current in the dark and thus to the reverse bias dark current of perovskite photodiodes. The insights into the ultimate origin of the dark current in perovskite photodiodes will be of great interest in perovskite electronics and optoelectronics.

Abstract

Minimizing reverse bias dark current density (J _dark) while retaining high external quantum efficiency is crucial for promising applications of perovskite photodiodes, and it remains challenging to elucidate the ultimate origin of J _dark. It is demonstrated in this study that the surface defects induced by iodine vacancies are the main cause of J _dark in perovskite photodiodes. In a targeted way, the surface defects are thoroughly passivated through a simple treatment with butylamine hydroiodide to form ultrathin 2D perovskite on its 3D bulk. In the passivated perovskite photodiodes, J _dark as low as 3.78 × 10^-10 A cm^-2 at -0.1 V is achieved, and the photoresponse is also enhanced, especially at low light intensities. A combination of the two improvements realizes high specific detectivity up to 1.46 × 10¹² Jones in the devices. It is clarified that the trap states induced by the surface defects can not only raise the generation-recombination current density associated with the Shockley–Read–Hall mechanisms in the dark (increasing J _dark), but also provide additional carrier recombination paths under light illumination (decreasing photocurrent). The critical role of surface defects on J _dark of perovskite photodiodes suggests that making trap-free perovskite thin films, for example, by fine preparation and/or surface engineering, is a top priority for high-performance perovskite photodiodes.

A versatile self-assembled molecule (SAM) designed as a hole transport material layer enables impressive efficiencies of 18.63% and 26.24% for wide-bandgap perovskite solar cells and 4-terminal all-perovskite tandem devices with long operational stability. Universality is successfully explored for state-of-the-art organic solar cells, illustrated by 18.84% efficiency for a PM6:BTP-eC9 system. This study is expected to inspire design of new SAMs for broad application prospects.

Abstract

Perovskite solar cells (PSCs) and organic solar cells (OSCs) face device efficiency losses and instability challenges with existing hole transport materials (HTMs). The development of new universal HTMs is in great demand to promote their practical applications. Herein, a versatile self-assembled molecule (SAM) based HTM is designed for record-high efficiency wide-bandgap (WBG, E_g >1.75 eV) PSCs, all-perovskite tandem solar cells (TSCs) and OSCs. The SAM exhibits high transmission and a lower-lying energy level, enabling enhanced interfacial charge transfer and suppressed non-radiative recombination losses. SAM based WBG PSCs deliver a maximum power conversion efficiency (PCE) of 18.63% with over 90% efficiency retention after 250 h continuous work. By stacking the optimal WBG PSC and a narrow-bandgap PSC bottom cell, the 4-terminal all-perovskite TSC achieves a remarkable 26.24% PCE. More importantly, this SAM based HTM exhibits impressive generality in bulk heterojunction OSCs rivalling PEDOT:PSS, with an impressive PCE of 18.84% obtained for PM6:BTP-eC9 based devices. When scaling up the PM6:BTP-eC9 device to 0.5 cm² in area (0.71 cm × 0.71 cm), the SAM based OSCs afford a highest PCE of 16.33%. This work provides a perspective for the design of universal SAM based charge transport materials targeting PSCs and OSCs for facile large-area fabrication.

A pseudo halide-based ionic liquid, methylamine formate, is incorporated into FAPbI₃ perovskite to realize homogeneous and strong compressive strain to stabilize FAPbI₃ perovskite, as well as, enhance the crystallinity, reduce defects density, and prolong the carrier lifetime, which contributes to a record power conversion efficiency of 24.08% for FAPbI₃ inverted perovskite solar cells.

Abstract

Inverted (p-i-n) perovskite solar cells have drawn great attention due to their outstanding stability and low-temperature processibility. However, their power conversion efficiency (PCE) still lags behind conventional (n-i-p) devices mainly due to the lack of strategies to stabilize α-FAPbI₃ without changing the bandgap. In this work, a facile and effective strategy is reported to regulate the residual strain via pseudo halide-based ionic liquids incorporation to stabilize α-FAPbI₃ perovskite in inverted perovskite solar cells (PVSCs). The employment of methylamine formate (MAFa) ionic liquid enables a homogenously stronger compressive strain to restrain the transition of shared-corner PbI₆ octahedron into shared-face δ-FAPbI₃, as well as affecting the dynamic behavior of carriers and defects to achieve a record PCE (24.08%) among the reported inverted FAPbI₃ perovskite solar cells up to now. In addition, the MAFa incorporation results in enhanced device stability, unencapsulated PVSC retains over 90% of its initial efficiency after stored in ambient environment (RH:30 ± 5%) for 1000 h. This work provides an efficient strategy to realize efficient and stable α-FAPbI₃ based inverted PVSCs to further catch up with the conventional ones.

Sodium formate (NaFo) in a CsPbI₂Br perovskite solution as a crystallization agent, which induces the synergetic effect of cation engineering and pseudo-halide anion engineering, is introduced. The NaFo-incorporating CsPbI₂Br PSCs with dopant-free P3HT exhibits a power conversion efficiency of 17.7% with a fill factor (FF) of 84.5%, which is the highest FF value among CsPbI₂Br-based PSCs reported so far.

Abstract

Inorganic CsPbI₂Br perovskite has a substantial potential for triple-junction tandem solar cells as a top subcell, however it exhibits relative instability in the air compared with organic-inorganic perovskites as well as significantly lower efficiency than the theoretical efficiency limit. To further enhance the air-stability and efficiency of CsPbI₂Br-based perovskite solar cells (PSCs), it is vitally crucial to improve the crystallinity and passivate the defects within films that accelerate the phase transformation to the photo-inactive phase in the air. Here, it is reported that crystallization management via incorporating sodium formate (NaFo) in a CsPbI₂Br perovskite solution effectively leads to enlarged grain size and the reduced trap density. The Na⁺ cation and HOOC⁻ anion produce a synergistic effect for engineering the defects by acting as cation and pseudo-halide anion passivators, respectively. As a result, the NaFo-incorporating device shows an improved power conversion efficiency (PCE) of 17.7% with a fill factor (FF) of 84.5%. To the best of the authors' knowledge, this progressive FF value is the highest value among CsPbI₂Br-based PSCs reported thus far. In addition, the NaFo-incorporated device shows improved air stability compared to the control device, retaining over 95% of its initial PCE for 1000 hours under 10% relative humidity at room temperature without any encapsulation.

A record efficiency of 18.71% for flexible perovskite solar modules is achieved, with negligible hysteresis and excellent mechanical stability, by employing interface engineering. The good performance is due to the reduced defect density, better energy band alignment, good wettable surface, and the provided charge-transfer channel between the perovskite and the interface.

Abstract

The electron-transport layer (ETL) plays an important role in improving the performance of flexible perovskite solar cells (F-PSCs). Herein, a room-temperature-processed SnO₂:OH ETL is demonstrated, that exhibits reduced defect density, in particular lower oxygen vacancy concentration, with better energy band alignment and more wettable surface for quality perovskite deposition. More importantly, an efficient electron-transfer channel is produced between the ETL and the perovskite layer due to the formation of hydrogen bonds at the interface, resulting in enhanced electron extraction from the perovskite. As a result, the efficiency of a large-area (36.50 cm²) flexible perovskite solar module based on MAPbI₃ is increased to as high as 18.71%; this is thought to be the highest reported PCE value for flexible perovskite solar modules to date. In addition, it exhibits high durability while maintaining over 83% of its initial PCE after flexing test cycles. Further, F-PSCs with SnO₂:OH show remarkably long-term stability, owing to a high quality of the perovskite film and a strong coupling between the SnO₂:OH and perovskite layer caused by hydrogen bonds, which successfully inhibits moisture permeation.

Prolinamide (ProA) is introduced into the PbI₂ precursor solution, which improves the performance of perovskite solar cells (PSCs) by the competitive crystallization and efficient defect passivation of perovskite. The results indicate that ProA can lead to the increase of the energy barrier of crystallization and slows down the crystallization rate. Notably, ProA-assisted PSCs achieve 24.61% power conversion efficiency and high stability.

Abstract

Defects of perovskite (PVK) films are one of the main obstacles to achieving high-performance perovskite solar cells (PSCs). Here, the authors fabricated highly efficient and stable PSCs by introducing prolinamide (ProA) into the PbI₂ precursor solution, which improves the performance of PSCs by the competitive crystallization and efficient defect passivation of perovskite. The theoretical and experimental results indicate that ProA forms an adduct with PbI₂, competes with free I⁻ to coordinate with Pb²⁺, leads to the increase of the energy barrier of crystallization, and slows down the crystallization rate. Furthermore, the dual-site synergistic passivation of ProA is revealed by density functional theory (DFT) calculations and experimental results. ProA effectively reduces non-radiative recombination in the resultant films to improve the photovoltaic performance of PSCs. Notably, ProA-assisted PSCs achieve 24.61% power conversion efficiency (PCE) for the champion device and the stability of PSCs devices under ambient and thermal environments is improved.

(DOI: 10.1002/solr.202300174)

The above article, first published online as an accepted article on 25 April 2023 in Wiley Online Library (wileyonlinelibrary.com), has been withdrawn by agreement between the authors, the Editor-in-Chief Anna Troeger, and Wiley-VCH Verlag GmbH.

The authors requested a withdrawal due to problems with the reproducibility of the reported experimental data.

The cross-linked perovskite and phenyl-C61-butyric acid methyl ester (PCBM) layers by polydimethylsiloxane (PDMS) are applied. The hydrogen bond and Lewis acid–base interaction between PDMS and perovskite precursors effectively reduce formamidinium vacancy, passivating uncoordinated Pb defects and improving perovskite stability. Also, PDMS in the PCBM layer can suppress the auto-aggregation of the PCBM under light and thermal stress.

The operational stability of p–i–n perovskite solar cells (PSCs) is dramatically subjected to the quality of the perovskite light harvester and the interface layer atop the perovskite. Herein, a dual crosslinked functional layer strategy of using the versatile polydimethylsiloxane as an additive both in the perovskite layer and in phenyl-C61-butyric acid methyl ester interface layer, to improve the device tolerance against light, thermal, humidity, and bending stress, is reported. As a result, a promising power conversion efficiency of 21.6% (stabilized at 21.3%) for nickel oxide-based p–i–n PSCs is achieved. In addition, the unencapsulated devices maintain 97% of their initial efficiencies after continuous operation under 1 sun equivalent illumination at 60 °C with maximum power point tracking for 1000 h and 80% of their initial efficiencies exposed in ambient air for 500 h. The application of the aforementioned strategy in the flexible device also improves the bending mechanical stability, of which the corresponding flexible devices maintain 85% of their initial efficiencies after 1000 cycles at a radius of 8 mm.

Active SnO₂ crystal planes favor the nucleation and crystallization of perovskite, especially in the buried interfacial region which is evidenced by synchrotron-based GIWAXS. The fabricated flexible perovskite solar cells (PSCs) deliver very high power conversion efficiency (PCE) up to 23.57% (22.75%, certified), and corresponding flexible PSCs modules achieve a PCE of 17.79% with an aperture area of 24 cm².

Abstract

The tin (IV) oxide (SnO₂) electron transport layer (ETL) has been widely employed to fabricate high-performance perovskite solar cells (PSCs). It has been reported that carbon quantum dots (CQDs) can be used to enhance electron mobility of SnO₂. However, an in-depth understanding of the driving force in this process is still lacking. Here, a high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) is employed, for the first time, to reveal the SnO₂ crystal face changes with one new type of CQD doping. Synchrotron-based grazing incidence wide-angle X-ray scattering (GIWAXS) can penetrate the flexible substrate to detect the buried region of the perovskite layer, showing the crystallinity and phase purity of the perovskite are significantly improved with CQD-modified SnO₂. The flexible n-i-p PSCs delivers a power conversion efficiency (PCE) up to 23.57% (22.75%, certificated), which is one of the highest values for single-junction n-i-p flexible PSCs. The corresponding n-i-p flexible modules achieve a PCE of 17.79% with aperture area ~ 24 cm². Furthermore, the flexible PSCs show excellent stability, preserving ≈95% of their initial efficiency after 1200 h under 40% relative humidity and 1-sun light irradiation at 25 °C, and maintained > 90% of initial efficiency after 2500 bending cycles at a bending radius of 6 mm.

A series of novel self-assembled molecules (SAMs) is synthesized and successfully used to modify the interfacial layer between poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and perovskite. The introduction of SAMs improves interfacial contact, reduces nonradiative recombination, and improves the quality of perovskite films. Consequently, the all-perovskite tandem solar cell with an efficiency of 25.24% is realized.

Abstract

This study is on the enhancement of the efficiency of wide bandgap (FA_0.8Cs_0.2PbI_1.8Br_1.2) perovskite solar cells (PSCs) used as the top layer of the perovskite/perovskite tandem solar cell. Poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine] (PTAA) and the monomolecular layer called SAM layer are effective hole collection layers for APbI₃ PSCs. However, these hole transport layers (HTL) do not give high efficiencies for the wide bandgap FA_0.8Cs_0.2PbI_1.8Br_1.2 PSCs. It is found that the surface-modified PTAA by monomolecular layer (MNL) improves the efficiency of PSCs. The improved efficiency is explained by the improved FA_0.8Cs_0.2PbI_1.8Br_1.2 film quality, decreased film distortion (low lattice disordering) and low density of the charge recombination site, and improves carrier collection by the surface modified PTAA layer. In addition, the relationship between the length of the alkyl group linking the anchor group and the carbazole group is also discussed. Finally, the wide bandgap lead PSCs (E _g = 1.77 eV) fabricated on the PTAA/monomolecular bilayer give a higher power conversion efficiency of 16.57%. Meanwhile, all-perovskite tandem solar cells with over 25% efficiency are reported by using the PTAA/monomolecular substrate.

The resultant perovskite solar cells are intrinsically unstable owing to ion migration, which severely impedes performance enhancement, even with device encapsulation. This review aims to provide a thorough understanding of the origin of ion migration and the action of effective inhibition strategies that are essential for the development of “state-of-the-art” perovskite solar cells with high intrinsic stability to accelerate commercialization.

Abstract

In recent years, organic-inorganic halide perovskites are now emerging as the most attractive alternatives for next-generation photovoltaic devices, due to their excellent optoelectronic characteristics and low manufacturing cost. However, the resultant perovskite solar cells (PVSCs) are intrinsically unstable owing to ion migration, which severely impedes performance enhancement, even with device encapsulation. There is no doubt that the investigation of ion migration and the summarization of recent advances in inhibition strategies are necessary to develop “state-of-the-art” PVSCs with high intrinsic stability for accelerated commercialization. This review systematically elaborates on the generation and fundamental mechanisms of ion migration in PVSCs, the impact of ion migration on hysteresis, phase segregation, and operational stability, and the characterizations for ion migration in PVSCs. Then, many related works on the strategies for inhibiting ion migration toward highly efficient and stable PVSCs are summarized. Finally, the perspectives on the current obstacles and prospective strategies for inhibition of ion migration in PVSCs to boost operational stability and meet all of the requirements for commercialization success are summarized.

Nature Energy, Published online: 20 April 2023; doi:10.1038/s41560-023-01254-3

The performance of perovskite bifacial modules is still relatively poor. Now Gu et al. optimize the design of minimodules and achieve a power density of 23 mW cm−2 at an albedo of 0.2 and operational stability of 6,000 h.

Perovskite/Organic Tandem Solar Cells

In article number 2204347, Tingting Shi, Hin-Lap Yip, Man-Keung Fung, Yue-Min Xie, and co-workers aim to minimize the energy loss of perovskite/organic tandem solar cells (POTSCs) induced by compromised wide-bandgap perovskite sub-cells. An ionic liquid, methylammonium formate, is proposed to engineer the top and bottom all-inorganic perovskite (CsPbI₂Br) interfaces, which leads to passivated perovskite interfacial defects with reconstructed surfaces, therefore, high-efficiency POTSCs are obtained.

The effects of transport layers on perovskite lasing actions are investigated. It is find that a selected hole-transport layer (PTAA) can reduce the amplified spontaneous emission (ASE) threshold of perovskite by suppressing hot-hole-induced Auger loss. An independent excitation-wavelength-influenced ASE threshold experiment further verifies the discovery.

Abstract

Charge-transport layers are essential for achieving electrically pumped perovskite lasers. However, their role in perovskite lasing is not fully understood. Here, the role of charge-transport layers on the lasing actions of perovskite films is explored by investigating the amplified spontaneous emission (ASE) thresholds. A largely reduced ASE threshold and enhanced ASE intensity is demonstrated by introducing an additional hole transport layer poly(triaryl amine) (PTAA). It is shown that the key role of the PTAA layer is to accelerate the hot-carrier cooling process by extracting holes in perovskites. With reduced hot holes, the Auger recombination loss is largely suppressed, resulting in decreased ASE threshold. This argument is further supported by the fact that the ASE threshold can be further reduced from 25.7 to 7.2 µJ cm⁻² upon switching the pumping wavelength from 400 to 500 nm to directly avoid excess hot-hole generation. This work exemplifies how to further reduce the ASE threshold with transport layer engineering through hot-hole manipulation. This is critical to maintaining the excellent gain properties of perovskites when integrating them into electrical devices, paving the way for electrically pumped perovskite lasers.

Pemirolast potassium (PP) is employed to passivate Pb²⁺ and I atom defects, the release of residual stress can be effectively extended from the surface to the entire perovskite layer. Moreover, the superior carrier extraction/transport and better energy level alignment, yields an exceptional efficiency over 23% with an ultra-high fill factor of 84.36% for inverted perovskite solar cells.

Abstract

The quality of the perovskite absorption layer is critical for the high efficiency and long-term stability of perovskite solar cells (PSCs). The inhomogeneity due to local lattice mismatch causes severe residual strain in low-quality perovskite films, which greatly limits the availability of high-performance PSCs. In this study, a multi-active-site potassium salt, pemirolast potassium (PP), is added to perovskite films to improve carrier dynamics and release residual stress. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) measurements suggest that the proposed multifunctional additive bonds with uncoordinated Pb²⁺ through the carbonyl group/tetrazole N and passivated I atom defects. Moreover, the residual stress release is effective from the surface to the entire perovskite layer, and carrier extraction/transport is promoted in PP-modified perovskite films. As a result, a champion power conversion efficiency (PCE) of 23.06% with an ultra-high fill factor (FF) of 84.36% is achieved in the PP-modified device, which ranks among the best in formamidinium-cesium (FACs) PSCs. In addition, the PP-modified device exhibits excellent thermal stability due to the inhibited phase separation. This work provides a reliable way to improve the efficiency and stability of PSCs by releasing residual stress in perovskite films through additive engineering.

Carbonyl passivation of uncoordinated lead and inhibition of ion migration by amino groups achieve better effects. The champion performance of device based on 5-ADI additive achieved 22.42%

Perovskite solar cells (PSCs) have been developing rapidly in recent years, in which the choice of additives plays a crucial role. Herein, a new small molecule is introduced named 5-ADI with amino and carbonyl groups as an additive for perovskite. Specifically, the carbonyl group in 5-ADI can interact with undercoordinated Pb²⁺ to passivate the perovskite defects. Moreover, the amino group can effectively immobilize I⁻ atoms and inhibit ion migration, and it can synergistically passivate defects and improve photovoltaic performance. Meanwhile, the 5-ADI treatment makes energy levels match well. Consequently, high-quality perovskite film with fewer defects is produced due to 5-ADI treatment improves the crystallinity of perovskite. The device fabricated with 5-ADI additive achieves a power conversion efficiency of 22.42%. Besides, 5-ADI can act as a barrier against water to promote perovskite moisture stability. In general, a superior strategy for defect passivation in PSCs is provided.

A surface reconstruction strategy is employed to achieve a strain-free perovskite film with simultaneously reduced defect density, suppressed ion migration, and improved energy level alignment. The resultant monolithic perovskite/black-silicon tandem realizes a certified stabilized efficiency ≈29.0%, which is among the best performances for perovskite/silicon tandems based on tunnel oxide passivated contacts.

Abstract

Despite the swift rise in power conversion efficiency (PCE) to more than 32%, the instability of perovskite/silicon tandem solar cells is still one of the key obstacles to practical application and is closely related to the residual strain of perovskite films. Herein, a simple surface reconstruction strategy is developed to achieve a global incorporation of butylammonium cations at both surface and bulk grain boundaries by post-treating perovskite films with a mixture of N,N-dimethylformamide and n-butylammonium iodide in isopropanol solvent, enabling strain-free perovskite films with simultaneously reduced defect density, suppressed ion migration, and improved energy level alignment. As a result, the corresponding single-junction perovskite solar cells yield a champion PCE of 21.8%, while maintaining 100% and 81% of their initial PCEs without encapsulation after storage for over 2500 h in N₂ and 1800 h in air, respectively. Remarkably, a certified stabilized PCE of 29.0% for the monolithic perovskite/silicon tandems based on tunnel oxide passivated contacts is further demonstrated. The unencapsulated tandem device retains 86.6% of its initial performance after 306 h at maximum power point (MPP) tracking under continuous xenon-lamp illumination without filtering ultraviolet light (in air, 20–35 °C, 25–75%RH, most often ≈60%RH).

NIR-transparent perovskite solar cells with power conversion efficiency (PCE) > 17% and excellent stability are demonstrated. 4T silicon/perovskite tandem solar cell with PCE > 26% is fabricated over an area of ≈80 mm². Top transparent-contact is deposited via industry-compatible process at room temperature. Also, silver electrode is replaced with copper to reduce the production cost.

Si-perovskite tandem photovoltaic devices in the four-terminal (4T) configuration could proffer a solution to the problems associated with the stability gap between the component perovskite and Si devices. The fabrication of NIR-transparent perovskite solar cells (PSCs) with the stable triple cation perovskite as the photo-absorber and subsequent integration with a Si solar cell in a 4T tandem device is reported. The critical development of the sputtered top transparent conducting electrode (TCE) layer and oxide buffer layer at room temperature (25 °C) leads to reproducible, highly efficient NIR-transparent PSCs of both small area (0.175 cm²) with power conversion efficiency (PCE) of 17.1% and large area (0.805 cm²) with PCE of 16.0%. Electrically disparate, optically coupled 4T tandem devices of the optimized PSCs with commercial monocrystalline PERC Si solar cells exhibit greater than 26% PCE. In addition to enabling industry-compatible TCE-based low-cost Si/perovskite tandem photovoltaics, this study could also be the gateway for the potential use in niche applications like building integrated photovoltaics.