CsPbI2Br Perovskite Solar Cells Research Articles

Effective surface treatment for efficient and stable inverted inorganic CsPbI2Br perovskite solar cells

The interest in all-inorganic perovskite solar cells (PSCs) featuring a p-i-n structure is on the rise, attributed to their superior heat resistance and adaptability with tandem cell methods. However, their progress has been far from the regular structure owing to the comparatively low open circuit voltage (Voc). This research employs phenylethylammonium iodide, incorporating various side groups, as passivators to tackle the previously mentioned problems and investigate their effects on passivation. It is found that a reduction of trap-state density in perovskite film was accomplished due to the PEAI effective passivation effect by establishing coordination with the under-coordinated Pb2+ ions. Furthermore, there was an enhancement in the alignment of energy levels at the CsPbI2Br perovskite/PCBM junction, resulting in better charge extraction from the CsPbI2Br layer to the charge transport layer. As a result, an improved champion efficiency of 14.26 % with a Voc of 1.11 V, Jsc of 16.21 mA/cm2, and FF of 79.28 % was yielded for the PEAI treatment inverted CsPbI2Br device, compared with the 12.15 % efficiency of the control device. Superior device stability was exhibited for the optimal PEAI-treated devices without encapsulation. This research validates the significance of a side group on a surface passivation molecule to effectively passivate defects and optimize energy levels, especially for boosting Voc.

Crystallization management of CsPbI2Br perovskites by PbAc2-incorporated twice spin-coating process for efficient and stable CsPbI2Br perovskite solar cells

CsPbI2Br perovskite solar cell has been extensively studied due to its exceptional thermal stability and relatively stable perovskite phase structure. However, the presence of bromine leads to a rapid crystallization rate of CsPbI2Br films, resulting in small grain size and high defect density. Additionally, CsPbI2Br demonstrates poor light absorption due to its wide bandgap. Therefore, it is crucial to control the crystallization rate and increase the film thickness to reduce defect density, enhance light absorption, and improve photovoltaic performance. In this study, we utilized a PbAc2-incorporated twice spin-coating (PTS) process to address these issues. Initially, PbAc2 was added to the CsPbI2Br precursor solution to form a CsPbI2Br film, which was then coated with the CsPbI2Br precursor solution to produce the PTS film. Ac− can delay the perovskite crystallization, leading to the formation of thicker and denser CsPbI2Br films. Moreover, lone-pair electrons of the oxygen atom provided by Ac− formed coordination bonds with under-coordinated Pb2+ ions to fill halogen ion vacancies, thereby reducing the defect density. Ultimately, the PTS CsPbI2Br device achieved a peak power conversion efficiency (PCE) of 16.19% and maintained 96.7% of its initial PCE over 1500 h at room temperature under 25% relative humidity without any encapsulation.

Effects of 3-Bromo-N-methylbenzylamine modification on CsPbI2Br perovskite films and perovskite solar cells

In this work, 3-Bromo-N-methylbenzylamine (3-B-N-MB) was designed to modify CsPbI2Br/hole transport layer interface to reduce the interfacial non-radiative recombination loss of all-inorganic CsPbI2Br perovskite solar cells (PSCs). The effects of 3-B-N-MB modification on the morphology, structure, optical absorption, defect concentration, carrier lifetime, energy level, hydrophobicity of CsPbI2Br perovskite film and device performance, and carrier dynamics, as well as their mechanisms were systematically studied. The results show that the lone pair electrons in the N atom of N-H group in strongly alkaline 3-B-N-MB is more conducive to coordinate with uncoordinated Pb2+/Cs+ in CsPbI2Br, meanwhile the H atom of N-H group in 3-B-N-MB can react with I−/Br− in CsPbI2Br through hydrogen bonding, passivating interface defects to increase grain size and enhance the crystallinity and density of CsPbI2Br films, optimizing interface energy level matching to promote carrier transport, thus suppressing interfacial non-radiative recombination to improve device performance. As a result, the PCE of the 3-B-N-MB modified PSCs significantly enhanced ∼32.5 % as compared to that of the pristine one and the air stability of the device has also improved. The 3-B-N-MB modification provides a new strategy to enhance the efficiency and stability of all-inorganic perovskite solar cells.

Bridging the buried interface with conjugated molecule for highly efficient carbon-based inorganic CsPbI2Br perovskite solar cells fabricated in air

Manipulating the buried interface of all-inorganic perovskite solar cells (PSCs) is essential to improve the performance of devices. However, the conventional modifiers of interface typically present insulating feature that can impede the transportation of carrier, leading to an inferior charge transport efficiency. Herein, we propose a conjugated molecule, 2,4-hexadienoic acid potassium salt, which can act as a bridge at the buried interface of device and improve the crystallization of perovskite film. Besides, this interfacial modifier also promotes larger and denser grains, passivating defects and suppress non-radiative recombination of buried interface. Simultaneously, the electrical performance of tin oxide film is enhanced and facilitate a better energy level alignment. Consequently, carbon electrodes-based PSCs (C-PSCs) are fabricated via a hot air-assisted method in air, and C-PSCs based on all-inorganic perovskite demonstrate significant enhancement of open circuit voltage (1.25 V) via conjugated molecule modification, and the power conversion efficiency (PCE) increase significantly from 10.86 % to 13.11 %. Moreover, unencapsulated target devices exhibit better stability than the control devices. This work offers a new idea to construct an interfacial bridge via conjugated molecule for efficient and stable C-PSCs fabricated in air.

Dual‐Doping Strategy of Metal Chlorides in Ambient Air with High Humidity for Achieving Highly Air‐Stable All‐Inorganic Perovskite Solar Cells

It is fundamentally challenging to achieve stable and efficient all‐inorganic perovskite solar cells (PSCs) in ambient air conditions for low‐cost commercial manufacturing, as the crystallinity, surface morphology, and optical activity of all‐inorganic perovskites exhibit high sensitivity to environmental factors such as moisture and illumination. Herein, a dual‐doping strategy is presented to prepare high‐quality dual‐doping CsPbI2Br films under ambient air with relative humidity of 70% (70% RH) by introducing CaCl2 and InCl3 additives into precursor solution. The results from the experiments and calculations reveal that the CaCl2 additive can isolate moisture by forming hydrates at the surface and grain boundary of perovskites. Meanwhile, the addition of InCl3 can significantly improve the optoelectronic properties via the heterovalent substitution of Pb2+ by a small amount of In3+. Moreover, the phase segregation can be significantly suppressed in the dual‐doping CsPbI2Br films owing to decreasing the electron–phonon coupling strength and increasing the activation energy of ion migration. The unencapsulated dual‐doping CsPbI2Br PSC with the power conversion efficiency (PCE) of 15.51% (70% RH) demonstrates high humidity storage and long‐term optical stability, remaining 90% of the original PCE after aging 2400 h under ambient air (50% RH) and 1500 h under continuous illumination, respectively.

Crystallization management and defect passivation via additive engineering for efficient and stable carbon-based CsPbI2Br perovskite solar cells

Inorganic CsPbI2Br perovskite solar cells (PSCs) have attracted enormous interest due to their excellent thermal stability and immense potential for application in tandem solar cells. However, the rambunctious crystallization and poor film quality of inorganic CsPbI2Br perovskite are the main factors limiting their performance improvement. Herein, dibenzoylmethane (DBM), containing electron-rich and dual CO functional groups, as an efficient precursor additive, is first introduced to regulate the crystallization of CsPbI2Br perovskite while passivating its associated defects. After DBM modification, nucleation is accelerated and the crystallinity of CsPbI2Br film is improved, thus promoting the phase stability. Additionally, DBM can passivate uncoordinated Pb2+ defects, thereby significantly reducing non-radiative recombination, and can also decrease the energy level difference between CsPbI2Br/Carbon. As a result, when DBM additive is incorporated in the CsPbI2Br, the power conversion efficiency (PCE) of the device with the fluorine doped tin oxide glass (FTO)/SnO2/CsPbI2Br/Carbon structure is significantly improved to 13.46 %, an increase of nearly 13 % compared to the control device (11.72 %). The unpackaged devices exhibit excellent air and thermal stability, still remaining over 90 % of its initial PCE after aging for 500 h under ambient conditions, or continuous heating at 65 °C in glovebox for 500 h, respectively.

Optimization of the performance of CsPbI2Br perovskite solar cells in air by adding polyethylene-graft-maleic anhydride and its mechanism

In this study, by adding Polyethylene-graft-maleic anhydride (PGMA) to the inorganic CsPbI2Br perovskite film, the coordination bonds and hydrogen bonds between PGMA and CsPbI2Br cooperate to passivate defects, regulate energy level and stabilize the perovskite structure and eventually improve the device performance. We systematically study the effects of PGMA addition on the morphology, structure, light absorption, defect concentration and carrier lifetime, hydrophobicity, and optical stability and room temperature black phase stability of CsPbI2Br films, and the photoelectric performance and air stability of PSCs, as well as their mechanism. The experimental results show that the addition of 3 wt% of PGMA greatly improves the photoelectric conversion efficiency (PCE) of CsPbI2Br PSCs by 40.19 % because of the synergistic passivation effects and energy level tuning. The hydrogen bonds between –CH2 in PGMA and I−/Br− in CsPbI2Br, along with the coordination of carbonyl groups with Cs+/Pb2+, improve carrier transport and collection by inactivating flaw and managing the level, reducing the non-radiative recombination losses. In addition, the PSCs with 3 wt% of PGMA maintain 80 % of their initial efficiency even after 600 h in high humidity air environment due to the synergistic effect of coordination bonds and hydrogen bonds. Our study provides valuable insights into the use of PGMA to improve the performance of all-inorganic CsPbI2Br PSCs and the practicality of perovskite solar cells.

Simultaneous Defect Passivation and Electric Level Regulation with Rubidium Fluoride for High-Efficiency CsPbI2Br Perovskite Solar Cells.

Due to the good balance of efficiency and stability, CsPbI2Br perovskite solar cells (PSCs) recently have attracted widespread attention. However, the improvement in photovoltaic performance for CsPbI2Br PSCs was mainly limited by massive defects and unmatched energy levels. Surface modification is the most convenient and effective strategy to decrease defect densities of perovskite films. Herein, we deposited rubidium fluoride (RbF) onto the surface of CsPbI2Br perovskite films by spin-coating. The numerous defects could be significantly passivated by RbF, resulting in suppressed nonradiative recombination. Furthermore, the CsPbI2Br perovskite film after RbF treatment exhibits a deeper Fermi level, and an additional built-in electric field forms to promote charge transport. Consequently, the champion device achieves a high efficiency of 10.82% with an improved VOC of 1.14 V, and it also exhibits excellent stability after long-term storage. This work offers a simple and effective approach to enhance the photovoltaic performance and stability of PSCs for broader applications in the future.

Crystallization Regulation and Lead Leakage Prevention Simultaneously for High-Performance CsPbI2Br Perovskite Solar Cells.

All-inorganic CsPbI2Br perovskite is striking as a result of the reasonable band gap and thermal stability. However, the notorious air instability, unsatisfactory conversion efficiencies, and toxic water-soluble Pb2+ ions have greatly limited the further development of CsPbI2Br-based devices. Herein, a facile strategy is developed to prepare efficient and air-stable CsPbI2Br-based perovskite solar cells (PSCs) with in situ lead leakage protection. With the introduction of 2,2'-dihydroxy-4,4'-dimethoxy-5,5'-disulfobenzophenone disodium salt (BP-9) into the CsPbI2Br precursor solution, the crystallization of perovskite can be regulated at a reduced trap density, the uncoordinated Pb2+ ions and electron-rich defects in the structure can be passivated to suppress non-radiative recombination, and the energy level arrangement can be optimized to improve charge carrier transport. Consequently, the optimized PSC achieved a championship efficiency of 17.11%, accompanied by negligible J-V hysteresis and remarkably improved air stability. More importantly, the strong chelation of BP-9 with water-soluble Pb2+ ions minimizes the leakage of toxic lead in the perovskite structure.

Organic-Hydrochloride-Modified ZnO Electron Transport Layer for Efficient Defect Passivation and Stress Release in Rigid and Flexible all Inorganic Perovskite Solar Cells.

All inorganic CsPbI2Br perovskite (AIP) has attracted great attention due to its excellent resistance against thermal stress as well as the remarkable capability to deliver high-voltage output. However, CsPbI2Br perovskite solar cells (PeSCs) still encounter critical challenges in attaining both high efficiency and mechanical stability for commercial applications. In this work, formamidine disulfide dihydrochloride (FADD) modified ZnO electron transport layer (ETL) has been developed for fabricating inverted devices on either rigid or flexible substrate. It is found that the FADD modification leads to efficient defects passivation, thereby significantly reducing charge recombination at the AIP/ETL interface. As a result, rigid PeSCs (r-PeSCs) deliver an enhanced efficiency of 16.05% and improved long-term thermal stability. Moreover, the introduced FADD can regulate the Young's modulus (or Derjaguin-Muller-Toporov (DMT) modilus) of ZnO ETL and dissipate stress concentration at the AIP/ETL interface, effectively restraining the crack generation and improving the mechanical stability of PeSCs. The flexible PeSCs (f-PeSCs) exhibit one of the best performances so far reported with excellent stability against 6000 bending cycles at a curvature radius of 5mm. This work thus provides an effective strategy to simultaneously improve the photovoltaic performance and mechanical stability.

Fluorinated organic ammonium salt passivation for high-efficiency and stable inverted CsPbI2Br perovskite solar cells.

All-inorganic CsPbI2Br inverted perovskite solar cells (PSCs) have drawn increasing attention because of their outstanding thermal stability and compatible process with tandem cells. However, relatively low open circuit voltage (Voc) has lagged their progress far behind theoretical limits. Herein, we introduce phenylmethylammonium iodide and 4-trifluoromethyl phenylmethylammonium iodide (CFPMAI) on the surface of a CsPbI2Br perovskite film and investigate their passivation effects. It is found that CFPMAI with a -CF3 substituent significantly decreases the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions and effectively suppresses the non-radiative recombination in the resulting PSC. In addition, CFPMAI surface passivation facilitates the optimization of energy-level alignment at the CsPbI2Br perovskite/[6,6]-phenyl C61 butyric acid methyl ester interface, resulting in improved charge extraction from the perovskite to the charge transport layer. Consequently, the optimized inverted CsPbI2Br device exhibits a markedly improved champion efficiency of 14.43% with a Voc of 1.12V, a Jsc of 16.31 mA/cm2, and a fill factor of 79.02%, compared to the 10.92% (Voc of 0.95V) efficiency of the control device. This study confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

Effective surface passivation for stable and high-performance inverted CsPbI2Br perovskite solar cells with efficiency over 15%

Inverted CsPbI2Br perovskite solar cells (PSCs) still suffer from substantially non-radiative recombination losses at the perovskite interface, which limits the future advancement of CsPbI2Br perovskite-based single- and multi-junction photovoltaic cells. Interfacial defect passivation of perovskite films is an effective approach for enhancing the performance of PSCs. In this study, we introduce thiophene halide salts with different side groups on the surface of CsPbI2Br films to passivate the inorganic perovskite film and investigate their passivation effects. Our studies show that the 2-thiophenemethylammonium iodide (TM) passivator with –CH2NH3I side group effectively mitigates the trap density of the perovskite film by forming coordination bonding with Pb2+ ions, thus significantly inhibiting the non-radiative recombination in the resulting PSC. In addition, after the TM treatment, the better energy-level alignment between the CsPbI2Br/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) interface is achieved, thus enhancing the charge extraction from perovskite to the charge transport layer. The resulting inverted CsPbI2Br device demonstrates a significantly enhanced champion efficiency of 15.07% with a Voc of 1.16 V, Jsc of 16.42 mA/cm2, and FF of 79.11%, compared to the 11.19% efficiency of the control device, and maintains >97% of the initial efficiency after being stored for over 1700 h in N2 atmosphere. This work confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

Fluorine substitutions engineering of benzotriazole‐based hole transport polymers toward high‐performance CsPbI2Br perovskite solar cells

AbstractDeveloping suitable hole transport materials is of utmost importance in the quest to enhance the performance of CsPbI2Br perovskite solar cells (PSCs). Among the various undoped hole transport materials (HTMs), D‐π‐A type polymers incorporating benzodithiophene (BDT) as the D unit and benzotriazole (BTA) as the A unit have shown promising potential. To further optimize the energy level and enhance the hole transport ability of these HTMs, we employed a fluorine substitution strategy to synthesize P‐BTA‐2F and P‐BTA‐4F based on the polymer P‐BTA‐0F. Subsequently, we investigated the impact of varying degrees of fluorine substitution on the properties of the polymer materials and the performance of the devices. As the number of F substitutions increases, the polymer energy level of the HTM gradually shifts downward, the face‐on stacking of the HTM strengthens, the hole mobility of the HTM increases, and the rate of hole extraction and transport becomes faster. Ultimately, the CsPbI2Br PSCs based on the P‐BTA‐4F HTM achieve the highest power conversion efficiency (PCE) of 17.68%. Those findings demonstrate that selecting an appropriate amount of fluorine substitution is crucial for regulating the performance of polymer HTMs and improving device efficiency.

Bottom-up multi-interface modification boosts the performance of carbon-based HTL-free all-inorganic CsPbI2Br perovskite solar cells

The inferior interface quality between CsPbI2Br perovskite and the electron transport layer (ETL) as well as carbon electrode limits the stability and power conversion efficiency (PCE) of hole transport layer (HTL) free carbon-based all-inorganic CsPbI2Br perovskite solar cells (C-IPSCs). Herein, perfluoropropionic acid (PFPA) is designed as a bottom-up multiple surface defect passivator that can simultaneously passivate perovskite/TiO2 interface and perovskite/carbon electrode interface. The comprehensive experiments demonstrate that PFPA can not only optimize the electron mobility, conductivity, and band structure of the TiO2 ETL through passivating oxygen vacancies (VO), but also diffuse to the upper surface of perovskite film through grain boundaries to passivate the surface lead defects, thereby facilitating the gradient alignment of the perovskite surface energy levels with the carbon electrode. At the same time, PFPA can effectively release the tensile stress at the interface of perovskite and reduce the delocalization state of the band tail caused by lattice distortion, so as to prepare high-quality perovskite films. As a result of the above interaction, the PCE of HTL-free CsPbI2Br C-IPSCs after PFPA modification is increased from 12.24% (control device) to 14.15%. In addition, the modified unencapsulated devices show superior long-term stability and thermal stability.

Enhanced Efficiency and Stability of Inverted CsPbI2Br Perovskite Solar Cells via Fluorinated Organic Ammonium Salt Surface Passivation.

All-inorganic perovskite solar cells (PSCs) have recently received increasing attention due to their outstanding thermal stability. However, the performance of these devices, especially for the devices with a p-i-n structure, is still inferior to that of the typical organic-inorganic counterparts. In this study, we introduce phenylammonium iodides with different side groups on the surface of the CsPbI2Br perovskite film and investigate their passivation effects. Our studies indicate that the 4-trifluoromethyl phenylammonium iodide (CFPA) molecule with the -CF3 side group effectively decreases the trap density of the perovskite film by forming interactions with the undercoordinated Pb2+ ions and significantly inhibits the nonradiative recombination in the derived PSC, leading to an enhanced open-circuit voltage (Voc) from 0.96 to 1.10 V after passivation. Also, the CFPA post-treatment enables better energy-level alignment between the conduction band minimum of CsPbI2Br perovskite and [6,6]-phenyl C61 butyric acid methyl ester, thereby enhancing the charge extraction from the perovskite to the charge transport layer. These combined benefits result in a significant enhancement of the power conversion efficiency from 11.22 to 14.37% for inverted CsPbI2Br PSCs. The device without encapsulation exhibits a degradation of only ≈4% after 1992 h in a N2 glovebox.

Effects of passivated molecular side group on inverted inorganic CsPbI2Br perovskite solar cells

The advancement of efficient and stable inverted CsPbI2Br perovskite solar cells (PSCs) is imperative for their unique advantages of eliminating detrimental dopants and enabling compatible processes with tandem cells in comparison with the regular structures. However, the progress of this structure lags due to its relatively low open circuit voltage (Voc). Herein, we present an effective surface passivation strategy using phenethylammonium iodides with a different side group to ameliorate the aforementioned issues. It has been observed that 4-methyl phenethylammonium iodide (MePEAI) with the –CH3 side group can effectively reduce the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions, thereby suppressing the nonradiative recombination. Additionally, this approach optimizes the energy-level alignment at the perovskite/PCBM interface. As a result, the optimized device demonstrates a substantially enhanced efficiency from 11.23 to 14.10 %. Furthermore, the MePEAI-treated device exhibits excellent long-term stability. The unencapsulated device retains 81.2 % of its initial power conversion efficiency (PCE) after being stored for over 2900 h in an N2 atmosphere.

DTBDT‐Based Polymer Hole Transport Materials for Low Voltage Loss CsPbI2Br Perovskite Solar Cells

AbstractThe power conversion efficiency (PCE) of CsPbI2Br perovskite solar cells (PSCs) is still far from the theoretical efficiency due to the pronounced losses in open‐circuit voltage (VOC). The VOC loss can be mitigated by employing an appropriate hole transport layer (HTL), which facilitates energy level alignment and minimizes interface recombination losses. In this work, two D‐π‐A type polymers are chosen, PE64 and PE65, as HTLs, where pentacyclic dithieno[2,3‐d; 2′,3′‐d “]benzo[1,2‐b; 4,5‐b”]dithiophene (DTBDT) as the D‐unit and quinoxaline (Qx) as the A‐unit. It is demonstrated that the polymer PE65 with chlorinated thiophene side chain on the DTBDT unit has an optimized molecular arrangement, improved energy level matching, and enhanced passivation with CsPbI2Br, effectively reducing the losses caused by radiative and non‐radiative recombination in CsPbI2Br PSCs. Finally, the CsPbI2Br PSCs utilizing PE65 as HTL achieve a power conversion efficiency (PCE) of 17.60% with a high VOC of 1.44 V. Furthermore, the PE64 and PE65 are also employed to construct inter‐connecting layers (ICLs) for tandem solar cells (TSCs). The CsPbI2Br/D18:Y6 TSCs based on PE65‐ICL yield a PCE of 22.32% with a high VOC of 2.25 V. This work demonstrates that pentacyclic DTBDT‐based polymers are also promising HTLs for high‐performance PSCs and TSCs.

Zirconium Doping to Enable High-Efficiency and Stable CsPbI2Br All-Inorganic Perovskite Solar Cells.

All-inorganic wide-bandgap perovskite CsPbI2Br has attracted much attention because of its inherent thermal stability and ideal bandgap for the front subcell of tandem solar cells (TSCs). However, the low power conversion efficiency (PCE) and poor moisture stability of CsPbI2Br still restrict its future commercialization. Herein, zirconium tetrachloride (ZrCl4) was doped into CsPbI2Br films to modulate the crystal growth and improve the film quality. The partial substitution of the B-site Pb2+ of CsPbI2Br with Zr4+ suppresses the unwanted phase conversion from the crystallized black α-phase to the δ-phase, resulting in improved phase stability. Consequently, the humidity and thermal stability of the film are greatly improved. Additionally, the incorporation of ZrCl4 suppresses nonradiative recombination and forms a matched energy-level alignment with the hole-transport layer (Spiro-OMeTAD). Benefiting from these features, the ZrCl4-doped CsPbI2Br perovskite solar cell (PSC) shows an outstanding efficiency of 16.60% with a high open-circuit voltage of 1.29 V. The unencapsulated devices simultaneously show excellent humidity and thermal stability, retaining over 91% of PCEinitial after 1000 h of aging in ambient air conditions and 92% PCEinitial after 500 h of continuous heating at 85 °C in a nitrogen environment, respectively. Furthermore, ZrCl4-doped CsPbI2Br was employed as the front subcell of perovskite/organic TSCs and achieved a remarkable PCE of 19.42%, showing great potential for highly efficient and stable TSCs.

Acetate-based ionic liquid engineering for efficient and stable CsPbI2Br perovskite solar cells with an unprecedented fill factor over 83%

The current investigation addresses the persistent challenge of poor ambient stability exhibited by inorganic lead halide perovskites, primarily stemming from intrinsic phase transitions and the presence of defect states. This area of research has been considerably unexplored thus far. On the other hand, the notable effects of ionic liquids (ILs) in improving both stability and efficiency of perovskite photovoltaics have been substantial. In line with these developments, this study endeavors to synergize these two critical domains by introducing an acetate (Ac)-based IL into the inorganic perovskite precursor solution to tailor the crystal growth and charge carrier dynamics in CsPbI2Br films, resulting in prolonged stability and enhanced photovoltaic performance. The integration of 1-butyl-3-methylimidazolium acetate (BMIMAc) can indeed accelerate the crystallization of the inorganic perovskite film by interacting the Ac− anion with uncoordinated Pb2+ cation in CsPbI2Br. This interaction prompts the formation of smaller grains, which in turn inhibits the creation of non-photoactive phases. Moreover, the presence of BMIMAc as a passivation agent introduces significant defect-healing capabilities, eliminated charge recombination, and increased hydrophobicity. This work endeavors to pave the way for high-efficiency, enduring, and more robust inorganic PSCs through the integration of innovative materials and advanced understanding of fundamental principles, resulting uniform and dense perovskite film. Accordingly, 1.1 mol% BMIMAc-passivated device enables an impressive efficiency of 15.6% with an unprecedented fill factor (FF) exceeding 83%. Remarkably, even after undergoing extended light-soaking for 600 h, the BMIMAc-passivated device retains approximately 85% of its initial efficiency.

Antisolvent-Free Heterogenous Nucleation Enabled by Employing 4-Tert-Butyl Pyridine Additive and Two-Step Annealing for Efficient CsPbI2Br Perovskite Solar Cells.

All inorganic perovskite based on CsPbI2Br has attracted significant attention due to its relatively thermal stable structure compare to its hybrid counterparts. With a wide bandgap of 1.9eV and excellent light absorption capability, it has been extensively explored for applications in indoor photovoltaics and as a front absorber in tandem devices. However, the uncontrollable crystallization process during solvent evaporation and thermal annealing leads to both macroscopic defects like cracks and microscopic defects such as voids. In this study, a metastable adduct with lead (II) halides by incorporating 4-tert-butyl pyridine as a volatile Lewis base monodentate ligand in the precursor solution is formed. The strategic preferential decomposition of the adduct during the early-stage low-temperature annealing facilitated the desorption of lead (II) halides, inducing antisolvent-free heterogenous nucleation. This, in turn, promoted crystal growth during subsequent high-temperature annealing, resulting in dense films with low defect density. As a result, a maximum open-circuit voltage of 1.30V is achieved with the champion power conversion efficiency of 16.5% in CsPbI2Br-based perovskite solar cell. The work reveals a new mechanism of using Lewis acid-base adduct to obtain high quality perovskite films other than hindering crystallization in traditional way.