JIALINGBO

W e present a new 1.80 eV wide-bandgap (WBG) perovskite treated with piperazinium iodide (PI) for all-perovskite tandem solar cells. This treatment eliminates non-radiative recombination losses and reduces defect density resulting in an open circuit voltage of 1.36 V and enhanced photostability. Combined with a narrow bandgap (NBG) perovskite, this enables a tandem cell with a certified scan efficiency of 27.5%.

Abstract

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (V _OC) are essential to further improve the tandem solar cells’ performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V V _OC, reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%.

Sufficient conversion of residual photoinstable PbI₂ into robust 1D perovskite (EMIMPbI₃) can improve device stability, while the formation of an interfacial dipole layer at the SnO₂/perovskite interface can reduce the energetic mismatch via a single process. The optimized device delivers an efficiency of 24.28 % and a remarkable open circuit voltage of 1.19 V, accompanied with excellent humidity and operational stability.

Abstract

Eliminating the undesired photoinstability of excess lead iodide (PbI₂) in the perovskite film and reducing the energy mismatch between the perovskite layer and heterogeneous interfaces are urgent issues to be addressed in the preparation of perovskite solar cells (PVSCs) by two-step sequential deposition method. Here, the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF₄) is employed to convert superfluous PbI₂ to more robust 1D EMIMPbI₃ which can withstand lattice strain, while forming an interfacial dipole layer at the SnO₂/perovskite interface to reconfigure the interfacial energy band structure and accelerate the charge extraction. Consequently, the unencapsulated PVSCs device attains a champion efficiency of 24.28 % with one of the highest open-circuit voltage (1.19 V). Moreover, the unencapsulated devices showcase significantly improved thermal stability, enhanced environmental stability and remarkable operational stability accompanied by 85 % of primitive efficiency retained over 1500 h at maximum power point tracking under continuous illumination.

Using cesium cyclopropane acids (C₃) gives high crystallization quality in an all-inorganic perovskite CsPbI₂Br prepared in a wide ambient moisture window (RH: 25–65 %). The resultant CsPbI₂Br solar cells exhibit a high efficiency (>17 %) and excellent environmental stability. The vaporization enthalpy of the side product DMA-acid (adjustable by C₃ loads) modifies the perovskite crystallization and device performance under different humidity.

Abstract

While all-inorganic halide perovskites (iHPs) are promising photovoltaic materials, the associated water sensitivity of iHPs calls for stringent humidity control to reach satisfactory photovoltaic efficiencies. Herein, we report a moisture-insensitive perovskite formation route under ambient air for CsPbI₂Br-based iHPs via cesium cyclopropane acids (C₃) as a compound introducer. With this approach, appreciably enhanced crystallization quality and moisture tolerance of CsPbI₂Br are attained. The improvements are attributed to the modified evaporation enthalpy of the volatile side product of DMA-acid initiated by Cs-acids. As such, the water-involving reaction is directed toward the DMA-acids, leaving the target CsPbI₂Br perovskites insensitive to ambient humidity. We highlight that by controlling the C₃ concentration, the dependence of power conversion efficiency (PCE) in CsPbI₂Br devices on the humidity level during perovskite film formation becomes favorably weakened, with the PCEs remaining relatively high (>15 %) associated with improved device stability for RH levels changed from 25 % to 65 %. The champion solar cells yield an impressive PCE exceeding 17 %, showing small degradations (<10 %) for 2000 hours of shell storage and 300 hours of 85/85 (temperature/humidity) tests. The demonstrated C₃-based strategy provides an enabler for improving the long-sought moisture-stability of iHPs toward high photovoltaic device performance.

A SnO_x interfacial layer with gradient compositions has been designed to overcome the dilemma between interface defects and electrical properties. Owing to the formation of homojunction, the gradient SnO_x structure facilitates the charge extraction, enabling the perovskite–silicon tandem solar cells based on industrially fully-textured silicon to achieve a certified efficiency of over 28%.

Abstract

Atomic layer deposition (ALD) growth of conformal thin SnO _x films on perovskite absorbers offers a promising method to improve carrier-selective contacts, enable sputter processing, and prevent humidity ingress toward high-performance tandem perovskite solar cells. However, the interaction between perovskite materials and reactive ALD precursor limits the process parameters of ALD-SnO _x film and requires an additional fullerene layer. Here, it demonstrates that reducing the water dose to deposit SnO _x can reduce the degradation effect upon the perovskite underlayer while increasing the water dose to promote the oxidization can improve the electrical properties. Accordingly, a SnO _x buffer layer with a gradient composition structure is designed, in which the compositionally varying are achieved by gradually increasing the oxygen source during the vapor deposition from the bottom to the top layer. In addition, the gradient SnO _x structure with favorable energy funnels significantly enhances carrier extraction, further minimizing its dependence on the fullerene layer. Its broad applicability for different perovskite compositions and various textured morphology is demonstrated. Notably, the design boosts the efficiencies of perovskite/silicon tandem cells (1.0 cm²) on industrially textured Czochralski (CZ) silicon to a certified efficiency of 28.0%.

Current and voltage matching via the adjustment of the cell width of perovskite and organic solar modules is experimentally demonstrated, enabling a higher-than-individual efficiency of 14.94% over an aperture area of 20.25 cm². Remarkably, the 2T mechanically-stacked tandem was built with modules having the non-complementary semiconductors FAPbBr₃ and PM6:Y6:PC₆₁BM, thus overcoming the bandgap restrictions imposed by a monolithic structure.

Photocurrent matching in conventional monolithic tandem solar cells is achieved by choosing semiconductors with complementary absorption spectra and by carefully adjusting the optical properties of the complete top and bottom stacks. However, for thin film photovoltaic technologies at the module level, another design variable significantly alleviates the task of photocurrent matching, namely the cell width, whose modification can be readily realized by the adjustment of the module layout. Herein, this concept is demonstrated at the experimental level for the first time for a 2T-mechanically stacked perovskite (FAPbBr₃)/organic (PM6:Y6:PCBM) tandem mini-module, an unprecedented approach for these emergent photovoltaic technologies fabricated in an independent manner. An excellent I _sc matching is achieved by tuning the cell widths of the perovskite and organic modules to 7.22 mm (PCE _PVKT-mod = 6.69%) and 3.19 mm (PCE _OPV-mod = 12.46%), respectively, leading to a champion efficiency of 14.94% for the tandem module interconnected in series with an aperture area of 20.25 cm². Rather than demonstrating high efficiencies at the level of small lab cells, this successful experimental proof-of-concept at the module level proves to be particularly useful to couple devices with non-complementary semiconductors, either in series or in parallel electrical connection, hence overcoming the limitations imposed by the monolithic structure.

Succinic acid derivative with multiple active sites and optimal spatial positions maximizes the defect binding energy, improves the film quality, and depresses the non-radiative recombination of the perovskite, giving a record efficiency of 25.41% for RbCsFAMA-based quadruple-cation perovskite devices.

Abstract

Minimizing interfacial charged traps in perovskite films is crucial for reducing the non-radiative recombination and improving device performance. In this study, succinic acid (SA) derivatives varying active sites and spatial configurations are designed to modulate defects and crystallization in perovskite film. The SA derivative with two symmetric Br atoms, dibromosuccinic acid (DBSA), exhibits the optimal spatial arrangement for defect passivation. Experimental and theoretical results indicate that the carboxyl group and atomic Br in DBSA synergistically interact with the under-coordinated Pb²⁺. Moreover, the strong electronegativity of Br efficiently stabilizes the formamidinium cation via electrostatic interaction. Consequently, film quality is significantly improved and non-radiative recombination is markedly depressed, resulting in a photoluminesence lifetime of exceeding 4 µs of and a carrier diffusion length of 3 µm. An exceptional efficiency of 25.41% (certified at 25.00%) along with a high fill factor of 84.39% and excellent long-term operational stability have been achieved finally.

The development of a damp-heat-stable multiple-cation perovskite solar cell by applying various surface treatment strategies and an effective encapsulation structure is presented. The best-performing device achieves 20.82% efficiency and shows superior stability for 500 h under conditions at 85 °C and 85% relative humidity. This shows great promise as a potential solution for the modularization of perovskite solar cells.

Multiple-cation perovskites have been extensively researched for stability enhancement, but limited literature exists on CsFAMA (CFM) solar cell stability under harsh temperature and humidity. This article focuses on the development of damp-heat-resistant CFM-based perovskite solar cells (PSCs) through the implementation of various surface treatment strategies, including antisolvent treatment (AST) control and alkyl-type interfacial passivation, while also proposing an effective encapsulation structure. The Cs⁺ ratio in Cs _x (FA_0.91MA_0.09)_1−x Pb(I,Br)₃ perovskites is varied in the range of x = 0 to 0.362, and the AST times are explored by adjusting from 8 to 15 s. Remarkably, a power conversion efficiency (PCE) is achieved with significant improvements in open-circuit voltage and fill factor at an AST time of 12 s. Through precise tuning of the Cs ratio to x = 0.17 (Cs_0.17(FA_0.91MA_0.09)_0.83Pb(I,Br)₃) and introduction of an octyl-ammonium iodide interlayer, the highest-performing device with a PCE of 20.82% is obtained. Additionally, a low-temperature vacuum lamination is employed, and the conducive tape in a twisted form is extended, which effectively seals the device. This results in superior stability for 500 h under damp-heat conditions at 85 °C and 85% relative humidity. This encapsulation method holds significant promise as a potential solution for the modularization of PSCs.

The bipolar photoresponse based on spontaneously formed wide-narrow bandgap-laminated perovskite films by BiI₃ doping is demonstrated. Under the visible/near-infrared (NIR) light, corresponding electrons are easier to be separated and transported by the SnO₂/PC₆₁BM to the bottom/top electrodes. Benefiting from the wavelength-dependent bipolar response, the signal secure optical communication (SOC) system is realized based on hidden properties of the bipolar signals.

Abstract

Perovskite photodetectors with bipolar photoresponse characteristics are expected to be applied in the field of secure optical communication (SOC). However, how to realize the perovskite photodetector with bipolar response remains challenging. Herein, by introducing bismuth iodide (BiI₃) into Sn-Pb mixed perovskite precursor solution, 2D perovskite FA₃Bi₂I₉ is spontaneously formed at the bottom to realize a wide-narrow bandgap-laminated perovskite film. Wavelength-dependent bipolar response is realized based on the absorption difference of the photoactive region with different bandgap combined with the carrier competition of the homotypic transport layer adopted in the as-fabricated photodetector. Under the visible/near-infrared (NIR) light irradiation, the bottom/top of the film generates a higher carrier concentration, where electrons are easier to be separated and transported by the SnO₂/PC₆₁BM to the bottom/top electrodes, respectively, resulting in a negative and positive bipolar response. Finally, based on positive NIR signal as the effective signal and negative visible signal as the interference signal, the SOC system is realized, where the positive NIR signal is well hidden by the negative visible signal. This work provides a simple and feasible strategy for fabrication of laminated perovskite films to achieve bipolar response.

Herein, an electron transport layer ink is designed using hybrid fullerenes composed of mixed C₆₀, phenyl C₆₁ butyric acid methyl ester, and indene-C₆₀ bisadduct. This electron transport layer exhibits high conductivity, good energy-level alignment, and low interfacial nonradiative recombination. The all-perovskite tandem solar modules achieve a champion power conversion efficiency of 23.3% (aperture area = 20.25 cm²).

Abstract

All-perovskite tandem solar cells offer the potential to surpass the Shockley–Queisser (SQ) limit efficiency of single-junction solar cells while maintaining the advantages of low-cost and high-productivity solution processing. However, scalable solution processing of electron transport layer (ETL) in p-i-n structured perovskite solar subcells remains challenging due to the rough perovskite film surface and energy level mismatch between ETL and perovskites. Here, scalable solution processing of hybrid fullerenes (HF) with blade-coating on both wide-bandgap (≈1.80 eV) and narrow-bandgap (≈1.25 eV) perovskite films in all-perovskite tandem solar modules is developed. The HF, comprising a mixture of fullerene (C₆₀), phenyl C₆₁ butyric acid methyl ester, and indene-C₆₀ bisadduct, exhibits improved conductivity, superior energy level alignment with both wide- and narrow-bandgap perovskites, and reduced interfacial nonradiative recombination when compared to the conventional thermal-evaporated C₆₀. With scalable solution-processed HF as the ETLs, the all-perovskite tandem solar modules achieve a champion power conversion efficiency of 23.3% (aperture area = 20.25 cm²). This study paves the way to all-solution processing of low-cost and high-efficiency all-perovskite tandem solar modules in the future.

Recent post-treatment technological reforms toward perovskite thin films are summarized, and the principal functions of the post-treatment strategies on the design of high-quality perovskite films are thoroughly analyzed. Then, the latest research progress of thermal annealing (TA)-related and TA-free techniques is summarized and discussed. Finally, an outlook of the prospect trends of these post-treatment techniques is given.

Abstract

Incredible progress in photovoltaic devices based on hybrid perovskite materials has been made in the past few decades, and a record-certified power conversion efficiency (PCE) of over 26% has been achieved in single-junction perovskite solar cells (PSCs). In the fabrication of high-efficiency PSCs, the postprocessing procedures toward perovskites are essential for designing high-quality perovskite thin films; developing efficient and reliable post-treatment techniques is very important to promote the progress of PSCs. Here, recent post-treatment technological reforms toward perovskite thin films are summarized, and the principal functions of the post-treatment strategies on the design of high-quality perovskite films have been thoroughly analyzed by dividing into two categories in this review: thermal annealing (TA)-related technique and TA-free technique. The latest research progress of the above two types of post-treatment techniques is summarized and discussed, focusing on the optimization of postprocessing conditions, the regulation of perovskite qualities, and the enhancement of device performance. Finally, an outlook of the prospect trends and future challenges for the fabrication of the perovskite layer and the production of highly efficient PSCs is given.

A fully aromatic carbazole-based self-assembled monolayer, denoted as MeO-PhPACz, is employed as a hole-selective layer (HSL) in inverted wide-band gap perovskite solar cells (PSCs). The fully aromatic configuration is crucial in promoting the formation of a dense and highly ordered HSL, improving hole extraction/transport efficiency. The optimized wide-band gap PSCs attain a power conversion efficiency (PCE) of 21.10 % and excellent UV resistance.

Abstract

Ultraviolet-induced degradation has emerged as a critical stability concern impeding the widespread adoption of perovskite solar cells (PSCs), particularly in the context of phase-unstable wide-band gap perovskite films. This study introduces a novel approach by employing a fully aromatic carbazole-based self-assembled monolayer, denoted as (4-(3,6-dimethoxy-9H-carbazol-9-yl)phenyl)phosphonic acid (MeO-PhPACz), as a hole-selective layer (HSL) in inverted wide-band gap PSCs. Incorporating a conjugated linker plays a pivotal role in promoting the formation of a dense and highly ordered HSL on substrates, facilitating subsequent perovskite interfacial interactions, and fostering the growth of uniform perovskite films. The high-quality film could effectively suppress interfacial non-radiative recombination, improving hole extraction/transport efficiency. Through these advancements, the optimized wide-band gap PSCs, featuring a band gap of 1.68 eV, attain an impressive power conversion efficiency (PCE) of 21.10 %. Remarkably, MeO-PhPACz demonstrates inherent UV resistance and heightened UV absorption capabilities, substantially improving UV resistance for the targeted PSCs. This characteristic holds significance for the feasibility of large-scale outdoor applications.

Herein, an effective redox strategy is developed to improve the quality of perovskite film by incorporating 4-fluorobenzothiohydrazide (FBTH) into cesium lead triiodide (CsPbI₃) precursor solution. A new compound FBTH-I is obtained, which can passivate the Pb-related defects and restrain I⁻ migration. Consequently, FBTH-treated CsPbI₃ perovskite solar cell (PSC) achieves a distinguished PCE of 21.41% with an excellent V _oc of 1.231 V and an outstanding operational stability.

Abstract

To simultaneously stabilize cesium lead triiodide (CsPbI₃) precursor solution and passivate the defects in CsPbI₃ film is greatly significant for achieving highly stable and efficient CsPbI₃ perovskite solar cells (PSCs). Herein, an effective redox 4-fluorobenzothiohydrazide (FBTH) is developed to stabilize the precursor solution and passivate iodine/lead-related defects for high-quality CsPbI₃ film. The comprehensive research confirms that 1) a new compound FBTH-I is obtained from an effective redox interaction between FBTH and molecular iodine (I₂) in perovskite precursor solution, which can effectively impede the formation of I₂ molecule and restrain I⁻ migration in perovskite film by forming N–H···I bond; 2) FBTH-I can also passivate Pb-related defects via forming S···Pb interaction. Consequently, the CsPbI₃ PSC based on FBTH-treated precursor solution exhibits a fascinating power conversion efficiency (PCE) of 21.41%, which is one of the highest PCE values among the reported pure CsPbI₃ PSCs so far, and an outstanding stability against the harsh conditions, such as thermal annealing and continuous light-illumination.

Nature Energy, Published online: 20 November 2023; doi:10.1038/s41560-023-01383-9

In this paper, the passivation of perovskite solar cells without Pb²⁺ defects was passivated through a reasonable molecular design. First, the passivation molecules CDT-N and CDT-S were designed and synthesized. Then, the passivation effect of passivation molecules on defects and the improvement effect on device efficiency and stability were studied. Finally, a perspective on future trends of passivation strategies is provided.

Abstract

The uncoordinated lead cations are ubiquitous in perovskite films and severely affect the efficiency and stability of perovskite solar cells (PSCs). In this work, 15-crown-5 with various heteroatoms are connected to the organic semiconductor carbazole diphenylamine, and two new compounds, CDT-S and CDT-N, are developed to modify the Pb²⁺ defects in perovskite films through the anti-solvent method. Apart from the oxygen atoms, there are also N atoms on crown ether ring in CDT-N, and both S and N heteroatoms in CDT-S. The heteroatoms enhance the interaction between the crown ether-based semiconductors and the undercoordinated Pb²⁺ defect in perovskite. Particularly, the stronger interaction between S atoms and Pb²⁺ further enhances the defect passivation effect of CDT-S than CDT-N, thereby more effectively suppressing the non-radiative recombination of charge carriers. Finally, the efficiency of the device treated with CDT-S is up to 23.05 %. Moreover, the unencapsulated device based on CDT-S maintained 90.5 % of the initial efficiency after being stored under dark conditions for 1000 hours, demonstrating good long-term stability. Our work demonstrates that crown ethers are promising in perovskite solar cells, and the crown ether containing multiple heteroatoms could effectively improve both efficiency and stability of devices.

Additive and passivator strategy is applied to fabricate wide-bandgap perovskite solar cells with bandgap of 1.68 eV. KSCN is introduced as additive and TEABr is used to passivate perovskite/C₆₀ interface, achieving a open-circuit voltage of 1.22 V. This leads to a power conversion efficiency of 22.02% for the champion device, which is one of the highest efficiencies at this bandgap.

Wide-bandgap (WBG) perovskite solar cells (PSCs) play a crucial role in tandem devices. However, the severe nonradiative recombination that occurs at the interface between perovskite and electron transport layer (ETL) leads to excessive open-circuit voltage (V _OC) loss, which hinders the further improvement of the photovoltaic conversion efficiency (PCE). To mitigate the V _OC loss in WBG PSCs, the defects in grains and grain boundaries are reduced as well as the energy-level alignment between perovskite layer and ETL, so as to improve the carrier collection efficiency, is optimized. Herein, potassium thiocyanate is introduced as an additive and 2-thiophenethylammonium bromide (TEABr) is used to passivate perovskite/C₆₀ interface. The synergistic treatment reduces the defect density and prolongs the carrier lifetime, implying that nonradiative recombination is effectively suppressed. Meanwhile, the energy-level alignment of the perovskite and C₆₀ is optimized, leading to the improvement of V _OC. Finally, WBG PSCs with a bandgap of 1.68 eV achieve a V _OC of 1.22 V (with a V _OC loss of 0.46 V) and a PCE of 22.02%.

The screen-printing technique is apromising fabrication method for making fully-printed perovskite solar cells (PSCs) for industrialization. Here, ionic liquid methylamine propionate with stronger coordination is introduced as a co-solvent to promote the escape of methylamine acetate molecules and the vertical growth of perovskite crystals. Fully screen-printed PSCs yields a champion power conversion efficiency of ≈17%, which is the record value for fully screen-printed PSCs.

Abstract

Using a screen-printing techniques is thought to be a good candidate for simplified, cost-effective, reliable, and scalable fabrication of fully printed perovskite solar cells (PSCs) for industrialization. Nevertheless, the screen-printing of perovskite film has not been realized until recently. This group finished the work using ionic liquid methylamine acetate (MAAc) as pure solvent. However, the space-confining effect during the perovskite crystallization in mesoporous impeded the escape of bottom MAAc molecules, which leads to the poor crystalline quality of the screen-printed film. In this work, ionic liquid methylamine propionate (MAPa) with stronger coordination is introduced as a co-solvent to promote the escape of MAAc molecules by forming the solvent volatilization channels in a confined mesoporous structure, which results in the complete MAAc volatilization and high filling degree of perovskite crystals inside the mesoporous structure. Also, MAPa promotes the vertical growth of perovskite crystals and coordinates with unbonded Pb²⁺ on the perovskite surface, leading to efficient charge transport and interfacial band alignment of the screen-printed film. Finally, fully screen-printed PSCs yields a champion power conversion efficiency (PCE) of ≈17%, which is the record value for fully screen-printed PSCs. Moreover, the unencapsulated device shows robust operational stability that maintains >85.3% of initial PCE (25%RH and 25 °C) under continuous illumination at the maximum power point after 250 h.

Nature, Published online: 23 October 2023; doi:10.1038/s41586-023-06745-7

Nature Energy, Published online: 19 October 2023; doi:10.1038/s41560-023-01377-7

Publication date: 15 December 2023

Source: Nano Energy, Volume 118, Part B

Author(s): Qi Zhang, Qiangqiang Zhao, Chenyang Zhang, Caidong Cheng, Kai Wang

A novel hole transport material (HTM) based on N-C=O resonance structure is designed for modulation the crystallization and bottom-surface defects of perovskite films. Benefiting from the resonance interconversion (N–C=O and N⁺=C–O⁻) in HTM, the large-area inverted perovskite solar cells (IPSCs) reach a high power conversion efficiency (PCE) up to 21.0% with excellent photo-thermal stability.

Abstract

Upscaling efficient and stable perovskite films is a challenging task in the industrialization of perovskite solar cells partly due to the lack of high-performance hole transport materials (HTMs), which can simultaneously promote hole transport and regulate the quality of perovskite films especially in inverted solar cells. Here, a novel HTM based on N–C = O resonance structure is designed for facilitating the modulation of the crystallization and bottom-surface defects of perovskite films. Benefiting from the resonance interconversion (N–C = O and N⁺ = C–O⁻) in donor-resonance-donor (D-r-D) architecture and interactions with uncoordinated Pb²⁺ in perovskite, the resulting D-r-D HTM with two donor units exhibits not only excellent hole extraction and transport capacities, but also efficient crystallization modulation of perovskite for high-quality photovoltaic films in large area. The D-r-D HTM-based large-area (1.02 cm²) devices exhibit high power conversion efficiencies (PCEs) up to 21.0%. Moreover, the large-area devices have excellent photo-thermal stability, showing only a 2.6% reduction in PCE under continuous AM 1.5G light illumination at elevated temperature (≈65 °C) for over 1320 h without encapsulation.

Publication date: 15 December 2023

Source: Nano Energy, Volume 118, Part A

Author(s): Ya Wang, Bo Zhou, Meidouxue Han, Juntao Zhao, Rongbo Wang, Jiawei Zhang, Huizhi Ren, Guofu Hou, Yi Ding, Ying Zhao, Xiaodan Zhang

In this work, by introducing ─NH₃ ⁺ rich proline hydrochloride as a versatile medium for buried interface in flexible perovskite solar cells, it not only provides a solid α-phase FAPbI₃ template but also prevents the phase transition induced degradation. A new record power conversion efficiency of 24.61% is achieved. Besides, the devices demonstrate excellent shelf-life/light soaking stability and mechanical stability.

Abstract

The buried interface of the perovskite layer has a profound influence on its film morphology, defect formation, and aging resistance from the outset, therefore, significantly affects the film quality and device performance of derived perovskite solar cells. Especially for FAPbI₃, although it has excellent optoelectronic properties, the spontaneous transition from the black perovskite phase to nonperovskite phase tends to start from the buried interface at the early stage of film formation then further propagate to degrade the whole perovskite. In this work, by introducing ─NH₃ ⁺ rich proline hydrochloride (PF) with a conjugated rigid structure as a versatile medium for buried interface, it not only provides a solid α-phase FAPbI₃ template, but also prevents the phase transition induced degradation. PF also acts as an effective interfacial stress reliever to enhance both efficiency and stability of flexible solar cells. Consequently, a champion efficiency of 24.61% (certified 23.51%) can be achieved, which is the highest efficiency among all reported values for flexible perovskite solar cells. Besides, devices demonstrate excellent shelf-life/light soaking stability (advanced level of ISOS stability protocols) and mechanical stability.

A full-scale defect passivation method that consists of an additive engineering strategy and two-stage annealing treatment is developed to passivate defects. Both deep- and shallow-level defects in the bulk, at the surface, and grain boundaries are passivated with improved energetic alignment and reduced non-radiative recombination. The devices achieve a champion efficiency of 24.20%, accompanied by greatly improved humidity, thermal, and illumination stabilities.

Abstract

Despite remarkable progress in perovskite solar cells (PSCs), the unsatisfying stability strongly interrelated with the defect density remains the main obstacle for commercialization. Herein, a synergetic defect passivation method is judiciously designed that consists of a precursor engineering strategy based on an ionic liquid 1-butylsulfonate-3-methylimidazolium dihydrogen phosphate (BMDP), and two-stage annealing (TSA) treatment to sufficiently passivate defects and enhance performance further. It is found that the multifunctional groups from BMDP have strong chemical interactions and form chelated complexes with perovskite components thus effectively passivating the intrinsic defects. Synergized by the sequential TSA treatment, the formed hydrophobic complexes can be precisely controlled with filling along grain boundaries (GBs) and on surfaces, leading to a wrapping of perovskite grains and significant passivation of GBs. Consequently, both deep- and shallow-level defects in the bulk, at GBs and surface are sufficiently passivated, resulting in a champion efficiency of 24.20%. Impressively, the resultant unencapsulated films and corresponding devices exhibit admirable stability with maintaining 83.9% of initial composition for 4000 h of aging in moist air, 81.7% original structure after continuous heating for 1600 h, and 97% initial power conversion efficiency for 1000 h under continuous illumination. This work provides an efficient strategy toward improved efficiency and stability PSCs.

Publication date: 15 December 2023

Source: Nano Energy, Volume 118, Part A

Author(s): Azhar Ali Ayaz Pirzado, Chaoqiang Wang, Xiujuan Zhang, Shuai Chen, Ruofei Jia, Huanyu Zhang, Jinwen Wang, Tehinke Achille Malo, Jie Lin, Geng He, Erdi Akman, Jingsong Huang, Jiansheng Jie