All-inorganic Perovskite Solar Cells Research Articles

Defect passivation strategy for inorganic CsPbI2Br perovskite solar cell with a high-efficiency of 16.77%

All-inorganic halide perovskite solar cells (PSCs) have acquired great progress, especially CsPbI2Br. However, their photoelectric conversion efficiency (PCE) remains far below the theoretical predictions. Non-radiative recombination is one of the important issues affecting the photoelectric performance of the PSCs, and the defective lead ions derived from the evaporation of halide ions in the inorganic perovskite are the principal non-radiative recombination centers. Herein, the non-radiative recombination is effectively suppressed by introducing the N-methyl-2-pyrrolidone (NMP) as a Lewis base molecule to passivate the defective lead ions. Therefore, by adjusting the dosage of NMP, the smooth and pinhole-free CsPbI2Br perovskite film is obtained and the optimized device exhibits a champion PCE of 16.77% with an excellent fill factor (FF) of 0.80. This work proves the effectiveness of passivation using Lewis base molecules to prevent non-radiative recombination defects in inorganic perovskite.

All-Inorganic Perovskite Solar Cells: Status and Future

All-Inorganic Perovskite Solar Cells: Status and Future

Photo-assisted deposited titanium dioxide for all-inorganic CsPbI2Br perovskite solar cells with high efficiency exceeding 13.6%

All-inorganic perovskite solar cells advancing in phase and thermal stability are regarded as promising candidates for high-performance optoelectronic application. Herein, a photo-assisted deposited titanium dioxide was designed and utilized as the electron-transporting layer. Photo-assisted deposited titanium dioxide demonstrated a low interfacial recombination rate and high carrier extraction efficiency. Consequently, CsPbI2Br-based all inorganic perovskite solar cells exhibit power conversion efficiencies of up to a value of 13.69%. This photo-assisted deposition method is a promising approach for scalable, convenient, and inexpensive fabrication in the future.

Heterogeneous photoresponse of individual grain in all-inorganic perovskite solar cells

Photoresponse is affected by the microscopic structure and orientation of the perovskite crystals, but it is difficult to quantify the individual grain size and always acts as homogeneous. Using scanning probe microscopy, the local electrical properties of individual grains in all-inorganic perovskites are mapped. Surface potential variations on lateral distance scales within or larger than one grain size are presented. Among perovskite grains, three discrete photoconductivity levels are identified, corresponding to the facet-dependent density of trap states, which was further demonstrated by the light intensity dependence of the local current–voltage curve of each grain.

Carbon-Based All-Inorganic CsPbI2Br Perovskite Solar Cells Using TiO2 Nanorod Arrays: Interface Modification and the Enhanced Photovoltaic Performance

Recently, carbon-based all-inorganic perovskite solar cells (PSCs) caught the attention of photovoltaic researchers due to their remarkable stability. Herein, we report a carbon-based all-inorganic CsPbI2Br PSC using TiO2 nanorod arrays (TiO2 NRAs) as an electron transporting layer. The method of using TiO2 NRAs as an electron pathway has the advantage of increasing the electron–hole separation effectively and enables a thicker active perovskite layer to obtain a stronger absorbance. In addition, a water–alcohol soluble CsCl was used to modify the interface between TiO2 NRAs and the CsPbI2Br active layer to reduce interfacial recombination of charge carriers in the cells, and the CsCl interface-modified device showed a 10.6% increase in the open-circuit voltage. An optimized power conversion efficiency of 11.45% has been obtained, which is one of the superior performances reported for the carbon-based pure CsPbI2Br PSCs to date.

Polymer-induced lattice expansion leads to all-inorganic CsPbBr3 perovskite solar cells with reduced trap density

All-inorganic perovskite materials (CsPbBr3) with long-term stability have been attracted enormous attention for commercialization. Here, a one-step spin-coating method was employed to yield high-purity CsPbBr3 perovskite films. The polyethylene glycol (PEG) was introduced into a precursor solution to balance the nucleation and growth rate. Noticeably, adding a polymeric material of PEG also leaded to a uniform lattice expansion in CsPbBr3 thin layers. The polymer-induced lattice expansion benefits the performances of a CsPbBr3 device due to reduced trap density, boosting the power conversion efficiency. This work emphasizes that controlled lattice expansion benefits in enhancing the electronic functionalities of perovskites.

Methylammonium Iodide-Mediated Controlled Crystal Growth of CsPbI2Br Films for Efficient and Stable All-Inorganic Perovskite Solar Cells.

A high-quality perovskite film is a key aspect contributing to high photovoltaic performance of all-inorganic perovskite solar cells. We herein demonstrate that the addition of methylammonium iodide (MAI) influences effectively both the tailored film morphology and precise crystal growth to construct high-quality CsPbI2Br films. It is found that an MAI additive retards the crystallization kinetics to control the inorganic perovskite films to form a highly crystalline α-CsPbI2Br structure consisting of microsized grains with reduced defect density. The optimal MAI additive (10 wt %) achieves a power conversion efficiency (PCE) of 10.40% for the CsPbI2Br-based all-inorganic perovskite solar cells, which is >30% enhancement from 6.95% of the pristine one. The solar cells employing the MAI additive possess high operational and thermal stability, retaining >70% of the original PCE after aging for 1500 h in ambient atmosphere and under continuous heating at 85 °C for 30 h, respectively. The photovoltaic performance with an indoor light source was also examined using a white light-emitting diode (6500 K, 1000 lux), showing promising PCEs of 23.51% with a stabilized power output of 21.15%.

Charge-Transporting-Layer-Free, Vacuum-Free, All-Inorganic CsPbIBr2 Perovskite Solar Cells Via Dipoles-Adjusted Interface.

The inorganic perovskite has a better stability than the hybrid halide perovskite, and at the same time it has the potential to achieve an excellent photoelectric performance as the organic-inorganic hybrid halide perovskite. Thus, the pursuit of a low-cost and high-performance inorganic perovskite solar cell (PSC) is becoming the research hot point in the research field of perovskite devices. In setting out to build vacuum-free and carbon-based all-inorganic PSCs with the traits of simple fabrication and low cost, we propose the ones with a simplified vertical structure of FTO/CsPbIBr2/carbon upon interfacial modification with PEI species. In this structure, both the electron-transporting-layer and hole-transporting-layer are abandoned, and the noble metal is also replaced by the carbon paste. At the same time, FTO is modified by PEI, which brings dipoles to decrease the work function of FTO. Through our measurements, the carrier recombination has been partially suppressed, and the performance of champion PSCs has far exceeded the control devices without PEI modification, which yields a power conversion efficiency of 4.9% with an open circuit voltage of 0.9 V and a fill factor of 50.4%. Our work contributes significantly to give an available method to explore charge-transporting-layer-free, low-cost, and high-performance PSCs.

Dual Interfacial Engineering Enables Efficient and Reproducible CsPbI2Br All-Inorganic Perovskite Solar Cells.

CsPbI2Br all-inorganic perovskite has shown superior photovoltaic properties particularly excellent phase and thermal stability, while the complicated film growth process requires additional research. Herein, the nucleation and crystallization process of the CsPbI2Br perovskite film is assisted by methyl acetate anti-solvent treatment. Additionally, a tailored SnO2 nanoparticle/TiO2 nanocrystal structured double electron transport layers (ETLs) is designed to remove the interfacial energy barrier, thus enhancing charge transfer and decrease charge recombination at the CsPbI2Br/ETL interfaces. Through synergistically dual interfacial engineering, we have demonstrated the preparation of a compact CsPbI2Br polycrystalline film with ordered and homogeneous grain size as well as ideal interfacial energy level alignment. In consequence, stable CsPbI2Br all-inorganic perovskite solar cells with the best power conversion efficiency of 15.86% has been successfully achieved together with a high open-circuit voltage of 1.23 V and a fill factor of 82.29%. We believe that the results here demonstrate efficient approaches to achieve high-quality inorganic perovskites for promoting their optoelectronic applications.

Black phosphorus quantum dots as an effective perovskite interfacial modification layer for efficient low-temperature processed all-inorganic CsPbI2Br perovskite solar cells

Developing high-performance perovskite solar cells (PSCs) with all of the functional layers fabricated at low temperature (<180 °C) is highly desirable for the roll-to-roll processing of CsPbI2Br based PSCs. As for the all-inorganic perovskite, it is still a challenge to obtain void-free perovskite film especially prepared at this condition. Herein, we develop a facile approach to optimizing the morphology of low-temperature processed all-inorganic perovskite via using black phosphorus quantum dots (BPQDs) as an excellent interfacial modification material atop the perovskite layer for the first time. It is found that high-electron-mobility BPQDs can fill the voids between the grains of the perovskite film to provide more efficient pathways for electron extraction. Moreover, the BPQDs modification can effectively reduce the surface trap density of the perovskite layer, in addition to enhance the absorption of the PSC, thus suppressing nonradiative recombination losses. As a result, by incorporating BPQDs as the interfacial modification layer, our designed all-inorganic PSCs produce a maximum PCE of up to 12.2%. Furthermore, such highly efficient CsPbI2Br based PSC combined with the full low-temperature processing is rare, even outperforming most of previously reported CsPbI2Br based PSCs.

Polymer hole-transport material improving thermal stability of inorganic perovskite solar cells.

Cesium-based inorganic perovskite solar cells (PSCs) are paid more attention because of their potential thermal stability. However, prevalent salt-doped 2,2',7,7'-tetrakis(N,N-dipmethoxyphenylamine)9,9'-spirobifluorene (Spiro-OMeTAD) as hole-transport materials (HTMs) for a high-efficiency inorganic device has an unfortunate defective thermal stability. In this study, we apply poly (3-hexylthiophene-2,5-diyl) (P3HT) as the HTM and design all-inorganic PSCs with an indium tin oxide (ITO)/SnO2/LiF/CsPbI3-xBrx/P3HT/Au structure. As a result, the CsPbI3-xBrx PSCs achieve an excellent performance of 15.84%. The P3HT HTM-based device exhibits good photo-stability, maintaining ∼80% of their initial power conversion efficiency over 280 h under one Sun irradiation. In addition, they also show better thermal stability compared with the traditional HTM Spiro-OMeTAD.

Making air-stable all-inorganic perovskite solar cells through dynamic hot-air

Abstract On 3rd August 2019 National Renewable Energy Laboratory (NREL) announced a new world record of 25.2% power conversion efficiency (PCE) for the hottest photovoltaic material known as perovskites. The growth in popularity and substantial improvement in the efficiency of perovskites since their discovery in 2009 is demonstrated by over 6000 publications in 2018. Although, the current world record efficiency has been reported for organic-inorganic halide perovskite, all devices were fabricated in controlled inert conditions and organic cations suffer from poor stability. Therefore, replacement of conventional organic cations by inorganic cations is one of the most promising approaches to make thermally stable photovoltaics. However, all-inorganic perovskite solar cells (PSCs) (herein AIPSCs) composition and deposition techniques limit the real-time stability. This article previews the dynamic hot air (DHA) method used for making CsPbI2Br-based perovskites with improved air-thermal stability using barium (Ba2+) alkaline earth metal ion doping. Interestingly, the feasibility of this DHA method toward large area fabrication is also demonstrated.

Efficient and Stable All-Inorganic Niobium-Incorporated CsPbI2Br-Based Perovskite Solar Cells.

Inorganic cesium lead halide perovskite (CsPbX3) is a promising light-harvesting material to increase the thermal stability and the device performance as compared to the organic-inorganic hybrid counterparts. However, the photoactive stability at ambient conditions is an unresolved issue. Here, we studied the influence of Nb5+ ions' incorporation in the CsPbI2Br perovskite processed at ambient conditions. Our results exhibited that 0.5% Nb-incorporated CsPb1-xNbxI2Br (herein x = 0.005) thin films show excellent uniformity and improved grain size because of the optimum concentration of Nb5+ doping and hot-air flow. The improved grain size and uniform film thickness deliver a superior interface between the CsPb1-xNbxI2Br layer and the hole-transporting material. The fabricated all-inorganic perovskite solar cell (IPVSC) devices exhibited the Nb5+ cation incorporation which enables decreased charge recombination, leading to negligible hysteresis. The champion device produces an open-circuit voltage (VOC) as high as 1.317 V. The IPVSC device containing a CsPb0.995Nb0.005I2Br composition delivers the highest power conversion efficiency of 16.45% under a 100 mW cm-2 illumination and exhibits a negligible efficiency loss over 96 h in ambient conditions.

Multifunctional Dye Interlayers: Simultaneous Power Conversion Efficiency and Stability Enhancement of Cs2AgBiBr6 Lead‐Free Inorganic Perovskite Solar Cell through Adopting a Multifunctional Dye Interlayer (Adv. Funct. Mater. 23/2020)

In article number 2001557, Wei Wang, Zongping Shao, and co-workers introduce a multifunctional dye interlayer into lead-free all-inorganic Cs2AgBiBr6-based perovskite solar cells to enhance the efficiency and stability by broadening the absorption spectrum, accelerating the charge carrier extraction, and constructing an appropriate energy level alignment. Consequently, the modified device delivers a higher power conversion efficiency of 2.84% and better stability under ambient conditions. Cover illustrator: Xiaoqing Yang.

Indium doped CsPbI3 films for inorganic perovskite solar cells with efficiency exceeding 17%

In recent years, all-inorganic perovskite materials have set off a research boom owing to features, such as good thermal stability, suitable bandgap, and fascinating optical properties. However, the power conversion efficiency (PCE) and the ambient stability of all-inorganic perovskite solar cells still remain a challenge. Herein, we investigate the effect of the addition of InI3 into CsPbI3 film on the corresponding device. InI3 incorporation could retard the crystallization process and control the growth rate of CsPbI3 polycrystalline films, yielding a high quality film with large grains and few voids. The increment in electrostatic potential and the reduction of carrier recombination enabled the open-circuit voltage of fabricated perovskite solar cell to be increased from 0.89 to 0.99 V. The champion device delivered a power conversion efficiency of 17.09%, which is higher than 14.36% for the reference device. And the InI3-included solar cell without any encapsulation retained 77% of its original efficiency after 860 h aging at room temperature in N2 condition.

Constructing highly efficient all-inorganic perovskite solar cells with efficiency exceeding 17% by using dopant-free polymeric electron-donor materials

Abstract Development of all-inorganic perovskite solar cells (PSCs) is highly desirable due to its excellent thermal stability and great potential for tandem solar cells. One main bottleneck that restricts its further development is the absence of the ideal hole-transporting materials which is critical to device performance and stability. Herein, we construct a brand-new architecture of all-inorganic PSCs via employing a series of doping-free polymeric organic photovoltaic donor materials as hole transport materials including J71, PBDB-T, PM6 with suitable energy level and carrier transport ability. The mechanism in terms of film molecular microscopic structure, electrical transport dynamics, electrical potential distribution were systematically investigated by grazing incidence wide-angle X-ray scattering (GIWAXS), conductive atomic force microscope (C-AFM) and kelvin probe force microscopy (KPFM) measurements. This work not only proposes a series of new dopant-free polymeric hole transporting materials for all-inorganic PSCs, but also demonstrates the fabrication of high efficiency devices with power conversion efficiencies over 17%, a record of all-inorganic PSCs based on dopant-free polymeric materials to our knowledge.

Solar Cells with High Short Circuit Currents Based on CsPbBr3 Perovskite-Modified ZnO Nanorod Composites

3-D all-inorganic perovskite solar cells have been built using vertically aligned conductive zinc oxide nanorods as the electron transport layer and optical waveguide. Yttrium doping improved the c...

Efficient All-Inorganic CsPbBr3 Perovskite Solar Cells by Using CdS/CdSe/CdS Quantum Dots as Intermediate Layers

Highly efficient all-inorganic perovskite solar cells require a fast charge transfer from CsPbBr3 to TiO2 to reduce the recombination from trap states. Herein, we insert a CdS/CdSe/CdS quantum dot (QD) layer between the TiO2 and CsPbBr3 layers to fabricate all-inorganic perovskite solar cells. By tuning the thicknesses of the CdSe layer of CdS/CdSe/CdS QDs, the conduction band (CB) levels can be adjusted to -3.72~-3.87 eV. After inserting the QD intermediate layer, the energy offset between the CB of TiO2 and CsPbBr3 is reduced, thus leading to a charge transfer rate boost from 0.040×109 to 0.059×109 s−1. The power conversion efficiency (PCE) of the solar cell with QD intermediate layer achieves 8.64%, which is 20% higher than its counterpart without QDs.

Promoting the Efficiency and Stability of CsPbIBr2-Based All-Inorganic Perovskite Solar Cells through a Functional Cu2+ Doping Strategy.

Although organic-inorganic halide perovskite solar cells (PSCs) have shown dramatically enhanced power conversion efficiencies (PCEs) in the last decade, their long-term stability is still a critical challenge for commercialization. To address this issue, tremendous research efforts have been devoted to exploring all-inorganic PSCs because of their intrinsically high structural stability. Among them, CsPbIBr2-based all-inorganic PSCs have drawn increasing attention owing to their suitable band gap and favorable stability. However, the PCEs of CsPbIBr2-based PSCs are still far from those of their organic-inorganic counterparts, thus inhibiting their practical applications. Herein, we demonstrate that by simply doping an appropriate amount of Cu2+ into a CsPbIBr2 perovskite lattice (0.5 at. % to Pb2+), the perovskite crystallinity and grain size are increased, the perovskite film morphology is improved, the energy level alignment is optimized, and the trap density and charge recombination are reduced. As a consequence, a decent PCE improvement from 7.81 to 10.4% is achieved along with an enhancement ratio of 33% with a CsPbIBr2-based PSC. Furthermore, the long-term stability of CsPbIBr2-based PSCs against moisture and heat also remarkably improved by Cu2+ doping. This work provides a facile and effective route to improve the PCE and long-term stability of CsPbIBr2-based all-inorganic PSCs.

BiBr3 as an additive in CsPbBr3 for carbon-based all-inorganic perovskite solar cell

Abstract The stable CsPbBr3 perovskite solar cell (PSC) has recently attracted wide attention, but its low photoelectric conversion efficiency is still the main concern at present. The quality of the perovskite absorber layer and the energy level matching between perovskite and hole transport layer (HTM) are important factors affecting the efficiency and stability of the PSCs. In this work, CsPbBr3 film is prepared by multi-step solution spin coating method. In preparation process, a layer of BiBr3 was modified on PbBr2 film before the CsBr coating to form CsPbBr3. This method can not only improve the crystal quality of perovskite, but also adjust the energy level to improve the carrier extraction. As the result, the photoelectric conversion efficiency (PCE) of carbon-based CsPbBr3 PSCs has been effectively improved to 8.73%. This work demonstrates an effective approach to the preparation of high-quality perovskite films.