hujiao

A low‐cost industrial organic pigment, quinacridone (QA), was applied as surface passivation agent for perovskite solar cells (PSCs) by solution processing of a soluble QA derivative followed by thermal annealing to convert it into insoluble QA. Passivation with strong interactions between QA molecules and metal halides, together with the hydrophobicity of QA coating, enabled highly efficient PSCs with remarkable stability.

Abstract

Surface passivation of perovskite solar cells (PSCs) using a low‐cost industrial organic pigment quinacridone (QA) is presented. The procedure involves solution processing a soluble derivative of QA, N,N‐bis(tert‐butyloxycarbonyl)‐quinacridone (TBOC‐QA), followed by thermal annealing to convert TBOC‐QA into insoluble QA. With halide perovskite thin films coated by QA, PSCs based on methylammonium lead iodide (MAPbI₃) showed significantly improved performance with remarkable stability. A PCE of 21.1 % was achieved, which is much higher than 18.9 % recorded for the unmodified devices. The QA coating with exceptional insolubility and hydrophobicity also led to greatly enhanced contact angle from 35.6° for the pristine MAPbI₃ thin films to 77.2° for QA coated MAPbI₃ thin films. The stability of QA passivated MAPbI₃ perovskite thin films and PSCs were significantly enhanced, retaining about 90 % of the initial efficiencies after more than 1000 hours storage under ambient conditions.

The strong interaction between F and Sn changes the electron cloud density around Sn atoms by introducing RbF into SnO₂ colloidal dispersion, contributing to the improved electron mobility of SnO₂. While spin‐coating RbF onto the SnO₂ surface, the Rb⁺ cations escape into the bulk perovskite, which inhibits ion migration and decreases the trap density.

Abstract

Regulating the electron transport layer (ETL) has been an effective way to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs) as well as suppress their hysteresis. Herein, the SnO₂ ETL using a cost‐effective modification material rubidium fluoride (RbF) is modified in two methods: 1) adding RbF into SnO₂ colloidal dispersion, F and Sn have a strong interaction, confirmed via X‐ray photoelectron spectra and density functional theory results, contributing to the improved electron mobility of SnO₂; 2) depositing RbF at the SnO₂/perovskite interface, Rb⁺ cations actively escape into the interstitial sites of the perovskite lattice to inhibit ions migration and reduce non‐radiative recombination, which dedicates to the improved open‐circuit voltage (V _oc) for the PSCs with suppressed hysteresis. In addition, double‐sided passivated PSCs, RbF on the SnO₂ surface, and p‐methoxyphenethylammonium iodide on the perovskite surface, produces an outstanding PCE of 23.38% with a V _oc of 1.213 V, corresponding to an extremely small V _oc deficit of 0.347 V.

Over 23% efficiency is achieved using a stabilized phenyl‐C₆₁‐butyric acid methyl ester (PCBM):bathophenanthroline (Bphen) interlayer in SnO₂‐based perovskite solar cells, which can retain over 92% of their initial efficiency after 1000 h continuous illumination of maximum power point tracking at 60 °C.

Abstract

It is crucial to make perovskite solar cells sustainable and have a stable operation under natural light soaking before they become commercially acceptable. Herein, a small amount of the small molecule bathophenanthroline (Bphen) is introduced into [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester and it is found that Bphen can stabilize the C₆₀‐cage well through formation of much more thermodynamically stable charge‐transfer complexes. Such a strengthened complex is used as an interlayer at the in‐light perovskite/SnO₂ side to achieve a champion device with efficiency of 23.09% (certified 22.85%). Most importantly, the stability of the resulting devices can be close to meeting the requirements of the International Electrotechnical Commission 61215 standard under simulated UV preconditioning and light‐soaking testing. They can retain over 95% and 92% of their initial efficiencies after 1100 h UV irradiation and 1000 h continuous illumination of maximum power point tracking at 60 °C, respectively.

An ionic liquid, 1,3‐dimethyl‐3‐imidazolium hexafluorophosphate (DMIMPF₆), was used to passivate a perovskite to decrease the defects of Pb‐cluster and Pb‐I antisite, thereby reducing the energy barrier between the perovskite and hole transport layer. A perovskite solar cell attained a 23.25 % efficiency with a high stability due to hydrophobic DMIMPF₆.

Abstract

Surface defects have been a key constraint for perovskite photovoltaics. Herein, 1,3‐dimethyl‐3‐imidazolium hexafluorophosphate (DMIMPF₆) ionic liquid (IL) is adopted to passivate the surface of a formamidinium‐cesium lead iodide perovskite (Cs_0.08FA_0.92PbI₃) and also reduce the energy barrier between the perovskite and hole transport layer. Theoretical simulations and experimental results demonstrate that Pb‐cluster and Pb‐I antisite defects can be effectively passivated by [DMIM]⁺ bonding with the Pb²⁺ ion on the perovskite surface, leading to significantly suppressed non‐radiative recombination. As a result, the solar cell efficiency was increased to 23.25 % from 21.09 %. Meanwhile, the DMIMPF₆‐treated perovskite device demonstrated long‐term stability because the hydrophobic DMIMPF₆ layer blocked moisture permeation.

High efficiency and humidity‐resistant flexible perovskite solar cells (FPSCs) are fabricated, using a SnO₂/Al(acac)₃ bilayer as the electron transfer layer. FPSCs present long‐time stability in ambient conditions (>50% relative humidity) without encapsulation, while yielding a power conversion efficiency (PCE) of up to 20.87%. That may open a new way to improve the stability of FPSCs.

Flexible perovskite solar cells (FPSCs) with high efficiency and excellent mechanical flexible properties have attracted enormous interest as a promising photovoltaic technology in recent years. However, the performance or stability of FPSCs is still far inferior to that of conventional glass‐based perovskite solar cells (PSCs). Herein, a cross‐linking agent called aluminum acetylacetonate (Al(acac)₃) is introduced as an interface layer between electron transport layer and perovskite absorber. Due to the well‐matched energy levels and improved grain size and crystallinity of the perovskite, a champion device with the highest power conversion efficiency (PCE) of 20.87% is achieved on the FPSCs. The device retains about 80% of its initial performance after 1000 h under >50% relative humidity without encapsulation. In addition, attributed to the Al(acac)₃ super bending resistance, more than 91% of the original PCE is retained after 1500 bending cycles. This work proposes the substrate side optimization for improving device efficiency and stability which may provide a novel concept for promoting the development of FPSCs.

Highly efficient CsPbI_1.5Br_1.5 perovskite solar cells (PSCs) are achieved via introducing fluorescein isothiocyanate (FITC) organic dye as passivator. FITC not only reduces the metal ion related trap states but also improves film crystallinity, resulting in an enhancement of device efficiency from 12.3% to 14.05%. In addition, it is demonstrated that CsPbI_1.5Br_1.5 perovskite shows the optimal halide composition for inorganic PSCs.

Abstract

All‐inorganic perovskite solar cells (PSCs) have recently received growing attention as a promising template to solve the thermal instability of organic–inorganic PSCs. However, the thermodynamic phase instability and relatively low device efficiency pose challenges. Herein, highly efficient and stable CsPbI_1.5Br_1.5 compositional perovskite‐based inorganic PSCs are fabricated using an organic dye, fluorescein isothiocyanate (FITC), as a passivator. The carboxyl and thiocyanate groups of FITC not only minimize the trap states by forming interactions with the under‐coordinated Pb²⁺ ions but also significantly increase the grain size and improve the crystallinity of the perovskite films during annealing. Consequently, perovskite films with superior optoelectronic properties, prolonged carrier lifetime, reduced trap density, and improved stability are obtained. The resulting device yields a champion efficiency of 14.05% with negligible hysteresis, which presents the highest reported efficiency for inorganic CsPbI_1.5Br_1.5 solar cells reported thus far. In addition, FITC can be generally adopted as attractive passivator to improve the performance of CsPbI₂Br‐ and CsPbIBr₂‐based PSCs. Furthermore, with a comprehensive comparison of mixed‐halide inorganic perovskites, it is demonstrated that CsPbI_1.5Br_1.5 compositional perovskite is a promising candidate with the optimal halide composition for high‐performance inorganic PSCs.

Publication date: April 2020

Source: Nano Energy, Volume 70

Author(s): Yang Liu, Yuchao Hu, Xinyang Zhang, Peng Zeng, Faming Li, Bin Wang, Qiang Yang, Mingzhen Liu

Publication date: April 2020

Source: Nano Energy, Volume 70

Author(s): Jung-Hye Kim, Quyet Van Le, Thang Phan Nguyen, Tae Hyung Lee, Ho Won Jang, Won Seok Yun, Soon Moon Jeong, JaeDong Lee, Soo Young Kim, Hyunmin Kim

Graphical abstract

Publication date: April 2020

Source: Nano Energy, Volume 70

Author(s): Junsheng Luo, Jianxing Xia, Hua Yang, Haseeb Ashraf Malik, Fei Han, Hongyu Shu, Xiaojun Yao, Zhongquan Wan, Chunyang Jia

The center won't hold : Introduction of V atoms with an optimal ratio into LaCoO₃ nanoparticles is used to manipulate the d‐band center and thus to facilitate the adsorption of intermediates of the oxygen evolution reaction. Moreover, the exchange interaction between high‐spin V⁴⁺ and low‐spin Co²⁺ promotes the formation of amorphous active species, which also cause more efficient oxygen evolution activity.

Abstract

Great efforts have been made to understand and upgrade the kinetically sluggish oxygen evolution reaction (OER). In this study, a series of V‐doped LaCoO₃ (V‐LCO) OER electrocatalysts with optimized d‐band centers are fabricated. When utilized as an electrode for the OER, as‐formed LaCo_0.8V_0.2O₃ (V‐LCO‐II) requires an overpotential of only 306 mV to drive a geometrical catalytic current density of 10 mA cm⁻². Furthermore, at a given overpotential of 350 mV, the OER current density of V‐LCO‐II is about 22 times that of pure LaCoO₃ (LCO) nanoparticles. Tailoring of the d‐band center by V doping facilitates the adsorption of OER intermediates and promotes the formation of amorphous active species on the surface of LCO through the exchange interaction between high‐spin V⁴⁺ and low‐spin Co²⁺. This work may create new opportunities for developing other highly active OER catalysts through d‐band center engineering.

Against the grain: Adding melamine maximizes grain size and minimizes defects in CsPbBr₃ perovskite films. The resulting CsPbBr₃ perovskite solar cell (PSC) free of encapsulation achieves a champion power conversion efficiency (PCE) of 9.65 % and excellent thermal and humidity stability.

Abstract

The preparation of high‐quality perovskite films with low grain boundaries and defect states is a prerequisite for achieving high‐efficiency perovskite solar cells (PSCs) with good environmental stability. An effective additive engineering strategy has been developed for simultaneous defect passivation and crystal growth of CsPbBr₃ perovskite films by introducing 1,3,5‐triazine‐2,4,6‐triamine (melamine) into the PbBr₂ precursor solution. The resultant melamine–PbBr₂ film has a loose, large‐grained structure and decreased crystallinity, which has a positive effect on the crystallization process of the perovskite as it retards the crystallization rate as a result of the interaction between melamine and lead ions. Additionally, the passivation by melamine gives a high‐quality CsPbBr₃ perovskite film with fewer grain boundaries, lower defect densities, and better energy level matching is achieved by multistep liquid‐phase spin‐coating, which greatly suppresses the nonradiative recombination resulting from the defects and promotes charge extraction at the interface. A champion power conversion efficiency as high as 9.65 % with a promising open‐circuit voltage of 1.584 V is achieved for PSCs with an architecture of fluorine‐doped tin oxide/c‐TiO₂/m‐TiO₂/melamine‐added CsPbBr₃/carbon‐based hole‐transporting layer. Furthermore, the unencapsulated melamine‐added CsPbBr₃ PSC shows superior thermal and humidity stability in ambient air at 85 °C or 85 % relative humidity over 720 h.

Incorporating formamidinium (FA) into methylammonium (MA) based perovskite has brought significant thermal and environmental stability including best device performance. It has been shown that addition of Cesium (Cs) makes perovskite robust in terms of thermodynamic stability as well. We explore the means of incorporating Cs into a base perovskite of mixed cation (FA/MA) and mixed halide (I/Br) that has a proven track record of high performance through an inter-diffusion approach. With this approach, it has been shown that perovskites form a smooth film without any residual PbI 2 and exhibit higher absorbance. Though the residual PbI 2 disappeared with the increase in added Cs, the film morphology became rough for Cs concentration higher than 15%. Addition of small amounts of PbCl 2 allowed inclusion of more Cs content, which resulted in smooth film surface and further improved device performance.

Metal halide perovskites have received substantial attention in research communities due to their outstanding efficiency achievements in the field of photovoltaics, optoelectronics and electronics, exhibiting extraordinary optical, electrical and mechanical properties. The exceptional structural tunability enables perovskite material to possess low-dimensional form at the atomic level and extends their applications into optoelectronic and photonic fields. This review discusses the recent progress of synthetic routes and fundamental optoelectronic properties of low-dimensional metal halide perovskites. In addition, the focus is to highlight the potential applications of perovskites in various devices including solar cells, light-emitting diodes, lasers, waveguides and memory devices. Finally, outlooks and the challenges that face the development of the perovskite materials in the near future are also presented.

Since the first report on solid-state perovskite solar cells (PSCs) with ∼10% power conversion efficiency (PCE) and 500 h-stability in 2012, tremendous effort has been being devoted to develop PSCs with higher PCE, longer stability and recycling hazardous lead waste. As a result, PCE over 23% was recorded in 2018 and stability over 10 000 h was reported. Beyond photovoltaics, lead halide perovskite materials demonstrated superb properties when they were applied to flat-panel x-ray detectors and non-volatile resistive switching memory. In this review, the progress of the lead halide perovskite in photovoltaics, x-ray imaging and memristors is investigated. Pb-based PSCs and non-Pb-based PSCs are compared, where technologies of non-Pb-based PSCs are not matured for commercialization. Pb-based PSCs were found to be highly suitable for both terrestrial and space photovoltaics. Higher sensitivity under low dose rate observed from the lead halide perovskite suggests a bright future fo...