CsPbBr3 Perovskite Solar Cells Research Articles

Energy Level Tuning in CsPbBr3 Perovskite Solar Cells through In Situ-Polymerized PEDOT Hole Transport Layer.

The all-inorganic CsPbBr3 perovskite solar cells exhibit excellent stability against humidity and thermal conditions as well as relatively low production cost, rendering them a gradually emerging research hot spot in the field of photovoltaics. However, the absence of a hole transport layer (HTL) in its common structure and the substantial energy level difference of up to 0.6 eV between the highest occupied molecular orbital (HOMO) level of CsPbBr3 and the work function of the carbon electrode have emerged as the primary factor limiting the improvement of its power conversion efficiency (PCE). In this work, the monomer 2,5-dibromo-3,4-ethylenedioxythiophene (DBEDOT) is spin-coated onto the surface of the CsPbBr3 film directly and then subjected to annealing; DBEDOT undergoes in situ polymerization to form poly(3,4-ethylenedioxythiophene) (PEDOT), which aims to ameliorate the issue of excessive energy level difference between CsPbBr3 and the carbon electrode, and to facilitate the extraction and transport efficiency of holes between the CsPbBr3 perovskite and the carbon electrode. Compared to the pristine device, the PCE of the device based on in situ polymerization is enhanced and achieves a maximum efficiency of 9.81%. Furthermore, the unencapsulated devices based on in situ polymerization maintain 95.9% of their original efficiency after 40 days of stability testing.

Colloidal Stabilizer‐Mediated Crystal Growth Regulation and Defect Healing for High‐Quality Perovskite Solar Cells

AbstractHigh‐quality perovskite (PVK) films is essential for the fabrication of efficient and stable perovskite solar cells (PSCs). However, unstable colloidal particles in PVK suspensions often hinder the formation of crystalline films with low defect densities. Herein, ethylenediaminetetraacetic acid (EDTA) as a colloidal stabilizer into lead iodide (PbI2) is introduced colloidal solutions. EDTA forms chelated complexes with Pb2+, enhancing the electrostatic repulsion and steric hindrance between colloidal particles. This stabilizes the particles and inhibits disordered motion (Brownian motion) and excessive aggregation. As a result, PbI2 films with a uniform hole distribution are formed, providing ample pathways for subsequent PVK film growth and sufficient space. During the film formation process, the replacement of molecules by formamidinium iodide (FAI) and EDTA slows down crystallization, ultimately leading to PVK films with large grain sizes and low defect density. By using this approach, champion power conversion efficiencies (PCEs) of 24.05% for FA0.97Cs0.03PbI3 PSC, 11.08% for CsPbBr3 PSC, and 25.19% for FA0.945MA0.025Cs0.03Pb(I0.975Br0.025)3 PSC are achieved. Moreover, the EDTA‐based FA0.97Cs0.03PbI3 device retains over 90% of its initial PCE after 1000 h at the maximum power point (MPP) under continuous illumination.

Multifunctional molecular bridge enabled interface passivation and strain release for stable and efficient all-inorganic perovskite solar cells

The precise management of the buried interface in n-i-p perovskite solar cells (PSCs) to achieve efficient charge extraction and transport is crucial for improving the photovoltaic performance. Here, a 4-chloro-2,5-dimethoxyaniline (CDA) modifier with multifunctional groups is utilized as a molecular bridge at the TiO2/CsPbBr3 buried interface to enhance the qualities of TiO2 and CsPbBr3 films and the arrangement of interface energy level. The chlorine atom in CDA can heal the oxygen vacancies defects on the TiO2 film surface, thereby improving its electron mobility and conductivity. The –O– and –NH2 groups in CDA play a passivation effect on the ions defects of CsPbBr3 film, and especially the two –O– groups can anchor the lattice Pb atoms of CsPbBr3 perovskite, which effectively reduce the trap states of CsPbBr3 film and release the residual lattice strain. The modification of CDA also improves the wettability and energy level of TiO2 film to optimize CsPbBr3 crystal growth and charge transport, respectively. Consequently, the CsPbBr3 PSCs with CDA molecular bridge free of encapsulation achieve a highly increased power conversion efficiency of 10.85 %, in contrast with 8.16 % value of the control device. After 720 h of storage at 85 °C and in air environment with 85 % relative humidity, the efficiency of the CDA-modified device retains 93.1 % of the initial value, demonstrating excellent long-term humidity and thermal stability.

Interfacial modulation by ammonium salts in hole transport layer free CsPbBr3 solar cells with fill factor over 86 %

CsPbBr3-based perovskite solar cells (PSCs) are potential candidates for the next-generation photovoltaic technology owing to their robust stability. Nevertheless, the inorganic CsPbBr3 PSCs using carbon electrode without hole transport layer usually suffer from severe non-radiative recombination loss at CsPbBr3/Carbon interfaces, thereby generating low fill factors (FFs) and further limiting the improvement of power conversion efficiencies (PCEs). To circumvent this issue, we proposed a universal interfacial engineering strategy to reduce the trap-assisted recombination through depositing butylammonium bromide (BABr) on the surface of CsPbBr3 films, which would enhance the FF and subsequent PCE of inorganic PSCs. The experimental results illustrate that the BABr modification could not only improve the morphology and phase purity of the inorganic perovskite films, but also adjust the energy level alignment between the CsPbBr3 layer and carbon electrode. After the optimization of BABr concentrations, we fabricated the BABr-modified device delivered an impressive PCE of 9.86 % with an extreme high FF over 86 %, which is one of the highest values achieved among the reported inorganic PSCs. Moreover, the PCE of unsealed CsPbBr3 device with BABr exhibited almost no attenuation after 90 days storage under the ambient atmosphere.

Preparation of Highly Efficient and Stable All-Inorganic CsPbBr3 Perovskite Solar Cells Using Pre-Crystallization Multi-Step Spin-Coating Method

All-inorganic CsPbBr3 perovskite solar cells have garnered extensive attention in the photovoltaic domain due to their remarkable environmental stability. Nevertheless, CsPbBr3 prepared using the conventional sequential deposition method suffers from issues such as inferior crystallinity, low phase purity, and poor film morphology. Herein, we propose a pre-crystallization methodology by introducing a minute quantity of CsBr into the PbBr2 precursor solution to generate a small amount of CsPb2Br5 crystals within the PbBr2 film, leading to a porous PbBr2 film with enhanced crystallinity. Under the influence of more pores and CsPb2Br5 crystals as nucleation sites for inducing growth, a CsPbBr3 film with a larger crystal size, lower grain boundary density, stronger crystallinity, and higher phase purity is formed. Compared with untreated devices, photovoltaic devices prepared using the pre-crystallization method achieved a champion photovoltaic conversion efficiency (PCE) of 8.62%. Furthermore, pre-crystallized devices demonstrate higher stability than untreated ones and can still retain 94% of the original PCE after being exposed to air for 1000 h without encapsulating.

Reducing oxygen vacancies of MoO3 by polyaniline functionalization for stable and efficient inorganic tri-brominated perovskite solar cells

The photovoltaic performance of perovskite solar cells (PSCs) is closely dependent on the efficient carrier extraction and transport at the interface. Here, a polyaniline (PANI) functionalized MoO3 (PANI/MoO3) hole transport material (HTM) is exploited to perfect the interface between the perovskite layer and carbon electrode in all-inorganic CsPbBr3 PSCs. After functionalization with PANI, the p-type behavior and the hole mobility and conductivity of MoO3 are improved by reducing the oxygen vacancies, which boosts the hole extraction and transport, energy level arrangement at the interface of CsPbBr3 perovskite/(PANI/MoO3) HTM. Meanwhile, the PANI/MoO3 with rich C–N and N–H groups introduced by PANI passivates the ions trap states of perovskite films by the C–N⋯Pb2+ (Cs+) Lewis acid-base coordination and the N–H⋯Br− hydrogen bonding, leading to an effective suppression of non-radiative recombination for improved carrier extraction. As a result, the PANI/MoO3 HTMs-based CsPbBr3 PSCs obtain a remarkably increased power conversion efficiency of 10.41 %, in comparison with the efficiency of the original device (6.55 %). In addition, the unencapsulated device with PANI/MoO3 HTMs shows excellent long-term stability with 93.9 % maintenance of the initial efficiency after storing in air with 85 % relative humidity and at 85 °C for 30 days.

Porous PbBr2 films modulation by indium tribromide additive for the fabrication of SnO2-based CsPbBr3 perovskite solar cells

The achievement of complete conversion of PbBr2 films presents a significant challenge in the development of CsPbBr3 films with consistent growth, comprehensive coverage, and controllable components. To address this challenge, introducing a porous structure in the planar PbBr2 film is advantageous for facilitating the immersion of CsBr precursor, thereby reducing impurity phase formation and mitigating strain caused by the film volume expansion. In order to accomplish this, indium tribromide (InBr3) was employed as an additive and the InBr3(DMF)3 adduct was utilized to expedite the release of organic molecules in PbBr2(DMF), resulting in the transformation of planar PbBr2 film into porous structures. The growth orientation of PbBr2 crystals was altered by this transformation, effectively suppressing the generation of metallic Pb impurities in the film. Additionally, it not only optimizes the morphology of CsPbBr3 film but also reduces impurity phase. As a result, the InBr3:CsPbBr3 perovskite solar cell achieved an efficiency of 7.28 %. The majority of In3+ ions were concentrated near the buried interface between SnO2 and InBr3:CsPbBr3, leading to significant improvements in both non-radiative recombination defect states within the perovskite film and electron injection and collection capabilities within the device.

Enhancing carrier collection in CsPbBr3 solar cells through crystal orientation and defect passivation

All-inorganic carbon-based CsPbBr3 perovskite solar cells (PSCs) have gained growing interest for their remarkable stability. However, compared to their organic–inorganic hybrid counterparts, there is still substantial room for improving their performance primarily due to the inferior photogenerated carrier collection efficiency. Here, we employ area-dependent transient photocurrent to assess the carrier transit time in CsPbBr3 PSCs, revealing that an extended carrier transit time relative to the lifetime significantly contributes to their low carrier collection efficiency. To address this challenge, we narrow the gap between carrier transit time and lifetime by introducing a dual-functional additive, serving to facilitate both crystallization orientation and defect passivation. Consequently, we achieve enhanced short-circuit current and efficiency in CsPbBr3 PSCs.

Optimization of the ETL titanium dioxide layer for inorganic perovskite solar cells

Titanium dioxide layers are the most popular electron transport layer (ETL) in perovskite solar cells. However most studies focuses on mesoporous structure and application with organic–inorganic hybrid perovskite. In this study, the topic of ETL in planar structure of inorganic CsPbBr3 perovskite solar cells was tackled, the presented approach will reduce production costs and improve cell stability, which is the greatest drawback of perovskite cells especially organic–inorganic perovskite. The potential application of these technology are greenhouses and building integrated PV sector. Here, the two TiO2 precursors titanium(IV) ethoxide in ethanol and titanium(IV) bis(acetylacetonate) diisopropoxide (Tiacac) were investigated, optimized and compared. TiO2 layers were deposited on high roughness FTO, without the use of a mesoporous layer, by spin coating method. The correlation between stock solution concentration and thickness of manufactured layers was tracked for both precursors as well as their difference in morphology of the final films and other properties. In particular, conformality and optical properties are better for Tiacac. Slightly lower refractive index of Tiacac-based titania reduced the reflective losses from 7.3 to 6.9% effectively. The obtained layers were used for inorganic solar cells of CsPbBr3 perovskite to finally settle the issue of optimal thickness and precursor. It is interesting that despite the supremacy in investigated properties of commonly used of the precursor Tiacac, the results of the cells pointed to the Tieth. The efficiency of the champion cell is 6.08% for Tieth, while 5.62% is noted for Tiacac. Trying to figure out this riddle, we shed a new light on the phenomena going on the ETL/inorganic perovskite interface investigating nanoroughness.

Isobutyramide Additive to Improve the Performance of CsPbBr3 Perovskite Solar Cells Prepared by Green Solvent

The inorganic cesium lead bromide (CsPbBr3) perovskite solar cell (PSC) is considered as an attractive option for new solar cells due to its outstanding stability. Preparing CsPbBr3 PSCs with H2O can effectively save costs and reduce the harm of toxic solvents to the environment. However, the poor contact property of the PbBr2 layer to the CsBr/H2O solution and the ability of water to dissolve the CsPbBr3 phase has a significant impact on the performance of the CsPbBr3 devices. In this article, isobutyramide is introduced into the PbBr2 film in the first step to improve the wettability of the PbBr2 film to CsBr/H2O solution, followed by spin‐coating of the 150 mg mL−1 CsBr/H2O solution on the PbBr2 film. Using this strategy, the fabricated PSCs with the architecture of FTO/compact‐TiO2/mesoporous‐TiO2/CsPbBr3 film/carbon demonstrate outstanding performance with a maximum efficiency of 9.59%. Furthermore, after 45 days of storage at ambient temperatures, the unencapsulated device retains more than 96% of its original efficiency. Therefore, this work provides a good demonstration for the preparation of high‐efficiency and eco‐friendly CsPbBr3 PSCs.

Cross‐layer all‐interface defect passivation with pre‐buried additive toward efficient all‐inorganic perovskite solar cells

AbstractThe buried interface in the perovskite solar cell (PSC) has been regarded as a breakthrough to boost the power conversion efficiency and stability. However, a comprehensive manipulation of the buried interface in terms of the transport layer, buried interlayer, and perovskite layer has been largely overlooked. Herein, we propose the use of a volatile heterocyclic compound called 2‐thiopheneacetic acid (TPA) as a pre‐buried additive in the buried interface to achieve cross‐layer all‐interface defect passivation through an in situ bottom‐up infiltration diffusion strategy. TPA not only suppresses the serious interfacial nonradiative recombination losses by precisely healing the interfacial and underlying defects but also effectively enhances the quality of perovskite film and releases the residual strain of perovskite film. Owing to this versatility, TPA‐tailored CsPbBr3 PSCs deliver a record efficiency of 11.23% with enhanced long‐term stability. This breakthrough in manipulating the buried interface using TPA opens new avenues for further improving the performance and reliability of PSC.

Bulk and interface passivation through potassium iodide additives engineering enables high-performance and humidity-stable CsPbBr3 perovskite solar cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have gained significant attention in the past decade due to their exceptional photovoltaic performance and unique advantages. However, the organic cation component of the hybrid perovskites results in poor humidity resistibility and thermal stability. Replacing organic cations with inorganic cations, such as Cs+, to fabricate all-inorganic CsPbX3 PSCs, is an effective way to improve their stability. Among the CsPbX3 PSCs, full-brominated CsPbBr3 PSCs have excellent moisture and thermal tolerance, with great potential for commercialization. However, these PSCs suffer from energy loss during operation, and their photoelectric conversion efficiency is lower than that of mainstream hybrid PSCs. Additive engineering is an effective method to improve the quality of perovskite films, which introduces functional additives into the perovskite precursor to induce perovskite crystallization, achieve the passivation of uncoordinated ions defects, and finely tune the energy level structures. In this study, Potassium iodide (KI) was added to the CsBr precursor solution to participate in the formation of the CsPbBr3 perovskite thin film. The partial substitution of A-site cation in the ABX3 perovskite occurred during the film formation, leading to beneficial variation of the crystal structure and photoelectronic performance in the CsPbBr3 system. The planar-architecture device based on the modified CsPbBr3 layer could reach a best efficiency of 10.06 %, together with a high open-circuit voltage (Voc) of 1.60 V. The KI-doped CsPbBr3 based PSC can retain over 90 % of the original PCE even after 30 days of aging, thanks to the diminished defect density by the KI passivation.

Enhanced efficiency and stability of inorganic CsPbBr3 perovskite solar cells based on carbon counter electrode by applying PbTiO3-coated TiO2 nanorod films as scaffold layers

The CsPbBr3 perovskite solar cells (PSCs) based on carbon counter electrode (CCE) are promising because of the advantages including fabrication simplicity and excellent stability, but their power conversion efficiencies (PCE) are low due to interfacial carrier recombination as the direct contact of the CsPbBr3 with electron transport materials (ETM). In this paper, PbTiO3 shells were grown onto TiO2 nanorods to form PbTiO3-coated TiO2 scaffold layer via a two-step method. The presence of PbTiO3 could promote crystallinity of the CsPbBr3 perovskite film and inhibits interface recombination at the CsPbBr3/TiO2 interface. Consequently, the carbon-based CsPbBr3 solar cells with PbTiO3/TiO2 scaffold layer achieves a high PCE of 7.28%, demonstrating an increase by 19.9% compared with the devices based on TiO2 NRs. Moreover, the champion devices exhibited excellent stability in ambient air, with the PCE value remaining at 93% over 28 days.

Reinforced SnO2 tensile‐strength and “buffer‐spring” interfaces for efficient inorganic perovskite solar cells

AbstractSuppressing nonradiative recombination and releasing residual strain are prerequisites to improving the efficiency and stability of perovskite solar cells (PSCs). Here, long‐chain polyacrylic acid (PAA) is used to reinforce SnO2 film and passivate SnO2 defects, forming a structure similar to “reinforced concrete” with high tensile strength and fewer microcracks. Simultaneously, PAA is also introduced to the SnO2/perovskite interface as a “buffer spring” to release residual strain, which also acts as a “dual‐side passivation interlayer” to passivate the oxygen vacancies of SnO2 and Pb dangling bonds in halide perovskites. As a result, the best inorganic CsPbBr3 PSC achieves a champion power conversion efficiency of 10.83% with an ultrahigh open‐circuit voltage of 1.674 V. The unencapsulated PSC shows excellent stability under 80% relative humidity and 80°C over 120 days.

Strengthened Buried Interface via Metal Sulfide Passivation Toward High‐Performance CsPbBr3 Perovskite Solar Cells

Although SnO2 has been widely used as the electron transport material (ETM) of the perovskite solar cells (PSCs), the energy level mismatch at the SnO2/CsPbBr3 buried interface is as high as 1 eV, which is disastrous for the CsPbBr3‐based PSCs. Herein, a buffer layer of metal sulfide (CdS, ZnS) is introduced to solve this problem. The power conversion efficiency (PCE) of CsPbBr3 PSCs has been increased from 8.16% to 9.48% for ZnS‐treated SnO2 (ZnS‐SnO2), and a champion efficiency of 10.61% has been achieved in CdS‐treated SnO2 (CdS‐SnO2) devices. Aside from the reduced energy loss, the mobility of the SnO2 ETM has been greatly enhanced after the metal sulfide treatment. The CdS‐SnO2 devices also enjoy the benefits of reduced defect density and speeded carrier extraction, contributing to an almost 30% performance enhancement. This 10.61% PCE is among the highly efficient CsPbBr3‐based PSCs reported to date. Finally, CdS‐SnO2 devices survive a harsh damp heat test (120 °C with a relative humidity of 50%) for a month with less than 15% efficiency loss, demonstrating the superior stability of our CsPbBr3 PSCs.

Methanol as an anti-solvent to improve the low open-circuit voltage of CsPbBr3 perovskite solar cells prepared with water.

CsPbBr3 has received more and more attention in the field of optoelectronic devices due to its excellent stability. To address the cost and environmental concerns associated with the use of toxic methanol, water has been explored as a substitute solvent for CsBr in the preparation of CsPbBr3 perovskite solar cells (PSCs). In this study, we utilized methanol as an anti-solvent of the CsBr/H2O solution to regulate the detrimental effects of water on the CsPbBr3 film and control the crystallization process. From results of the experiment, it was found that methanol anti-solvent treatment greatly improved the crystallization of the CsPbBr3 film, increased the grain size, and reduced the defect density. After the introduction of methanol anti-solvent treatment, the power conversion efficiency (PCE) increased from 6.09% to 7.91%, while the open-circuit voltage (Voc) increased from 1.18 V to 1.39 V. Furthermore, we incorporated 2-hydroxyethylurea into the CsPbBr3 PSCs to improve the wettability of PbBr2 towards the CsBr/H2O solution and ensure the formation of pure-phase CsPbBr3 films. The introduction of 2-hydroxyethylurea resulted in an additional increase in Voc from 1.19 V to 1.42 V. The PCE further improved from 6.56% to 8.62% after methanol anti-solvent treatment. These results demonstrate that methanol treatment effectively addresses the low Voc issue observed in CsPbBr3 PSCs prepared with water as a solvent. Importantly, this approach significantly reduces the reliance on methanol compared to conventional fabrication methods for CsPbBr3 PSCs. Overall, this work presents a promising pathway for achieving high Voc and efficiency in CsPbBr3 PSCs by utilizing water as a solvent.

Enhanced charge extraction enabled by amide-functionalized carbon quantum dots modifier for efficient carbon-based perovskite solar cells

The effective improvement of interfacial charge extraction and inhibition of charge recombination are crucial for promoting the performance of perovskite (PVK) solar cells (PSCs). Here, the N,N’-methylenebisacrylamide-functionalized carbon quantum dots (MBA/CQDs) with defects passivation effect and appropriate energy levels are proposed as a back interface modifier for carbon-based CsPbBr3 PSCs. The functionalization of MBA molecules not only increases the content of sp2 hybrid carbon in CQDs, but also expands the passivation effect of CQDs on surface defects of PVK films by introducing carbonyl and amino groups, which improves the carrier transport and reduces the carrier nonradiative recombination. Additionally, the modification of MBA/CQDs provides an intermediate energy level at the PVK/carbon back interface, which boosts hole extraction and lowers energy loss. Finally, a leading-edge power conversion efficiency of 10.40 % is derived for the MBA/CQDs modified champion device, which is significantly improved compared to the 7.02 % efficiency for the original CsPbBr3 PSCs. Furthermore, the unpackaged CsPbBr3 PSCs with MBA/CQDs have an excellent stability, maintaining an initial efficiency of 92 % after 30 days of storage at high humidity (85 % relative humidity) and temperature (85 °C) in air.

Enhanced efficiency and long-term stability of all inorganic CsPbBr3 perovskite solar cells via regulation of charge separation and extraction by band engineered-Co3O4 nanocrystals as a hole transport material layer

Insertion of an inorganic HTM intermediate at the CsPbBr3/Carbon interface can significantly improve photo-generated holes extraction efficiency without sacrificing advantages in device stability. Herein, low-cost and eco-friendly Co3O4 nanocrystals were synthesized by precipitation method and utilized as efficient inorganic HTM for CsPbBr3 PSCs. By regulating the hole quasi-fermi level (Ef, HTL) of the perovskite film with Co3O4 nanocrystals possessing a lower conduction band (CB), the built-in electric field (BEF) inside the CsPbBr3 can be reinforced, for which the Co3O4-induced energy level reconstruction facilitates fast charge separation and extraction because of the intensified driving force. In addition, the charge recombination behavior can be effectively inhibited. Finally, all inorganic CsPbBr3 PSCs with an architecture of FTO/c-TiO2/m-TiO2/CsPbBr3/Co3O4/carbon PSC realizes efficiency of 8.92% with an open-circuit voltage (Voc) of 1.531 V. Furthermore, the unencapsulated Co3O4-based PSC exhibits excellent stability in ambient air, keeping 98% of its initial efficiency after 90 days in 80% high humidity condition, and 97% of initial efficiency after 40 days in a high-temperature atmosphere of ∼80 °C.

Enhancing performance and stability of CsPbBr3 perovskite solar cells through environmentally friendly binary solvent fabrication

Enhancing performance and stability of CsPbBr3 perovskite solar cells through environmentally friendly binary solvent fabrication

Boosting the efficiency and stability of CsPbBr3 perovskite solar cells through modified multi-step spin-coating method

In this research, we enhance the stability of all-inorganic CsPbBr3 perovskite solar cells using a modified multi-step spin-coating technique. By introducing low-concentration CsBr and PbBr2 in two additional steps, we achieve a PbBr2 layer with fewer pinholes, improved crystallinity, and a smoother surface. This promotes the formation of a high-quality CsPbBr3 film with larger grains by incorporating a derivative-phase CsPb2Br5. This film reduces interface defects, enhances grain growth, and boosts power conversion efficiency from 5.43% to 9.36%. Notably, unencapsulated devices maintain stable performance for over 2400 h in ambient air conditions.