Anti-Dissociation Passivation via Bidentate Anchoring for Efficient Carbon-Based CsPbI2.6Br0.4 Solar Cells

Molecular passivation on perovskite surface is an effective strategy to inhibit surface defect-assisted recombination and reduce nonradiative recombination loss in perovskite solar cells (PSCs). However, the majority of passivating molecules bind to perovskite surface through weak interactions, resulting in weak passivation effects and susceptible to interference from various factors. Especially in carbon-based perovskite solar cells (C-PSCs), the molecular passivation effect is more susceptible to disturbance in subsequent harsh preparation of carbon electrodes via blade-coating route. Herein, bidentate ligand 2,2′-Bipyridine (2Bipy) is explored to passivate surface defects of CsPbI_2.6Br_0.4 perovskite films. The results indicate that compared with monodentate pyridine (Py), bidentate 2Bipy shows a stronger chelation with uncoordinated Pb(II) defects and exhibits a greater passivation effect on perovskite surface. As a result, 2Bipy-modified perovskite films display a significantly boosted photoluminescence lifetime, accompanied by excellent anchoring stability and anti-dissociation of passivating molecules. Meanwhile, the moisture resistance of the 2Bipy-modified perovskite films is also significantly enhanced. Consequently, the efficiency of C-PSCs is improved to 16.57% (J_sc = 17.16 mA cm⁻², V_oc = 1.198 V, FF = 80.63%). As far as it is known, this value represents a new record efficiency for hole transport material-free inorganic C-PSCs.     

Chromium-Based Metal–Organic Framework as A-Site Cation in CsPbI2Br Perovskite Solar Cells

Inorganic CsPbI_xBr_3−x perovskite solar cells (PSCs) have gained enormous interest due to their excellent thermal stabilities. However, their intrinsically poor moisture stability hampers their further development. Herein, a chromium-based metal–organic framework group is intercalated inside the inorganic Pb I framework, resulting in a new multiple-dimensional electronically coupled CsPbI₂Br perovskite. In this structurally and electronically coupled perovskite, the π-conjugated terpyridyl can delocalize the excited valence electrons of metal Cr³⁺ ion, enabling multi-interactive charge-carrier transport channels within CsPbI₂Br perovskites. The stability and efficiency of the produced devices are substantially enhanced in comparison to their counterparts with only a pristine CsPbI₂Br active layer. The optimized all-inorganic PSC yields a power conversion efficiency (PCE) as high as 17.02%. Remarkably, the stabilized device retains 80% of its PCE after 1000 h in the ambient atmosphere. This study provides a new paradigm toward addressing the stability challenge of the inorganic perovskite while enhancing its carrier transport ability.     

All-Inorganic CsPbI3 Quantum Dot Solar Cells with Efficiency over 16% by Defect Control

All-inorganic CsPbI₃ quantum dots (QDs) have shown great potential in photovoltaic applications. However, their performance has been limited by defects and phase stability. Herein, an anion/cation synergy strategy to improve the structural stability of CsPbI₃ QDs and reduce the pivotal iodine vacancy (V_I) defect states is proposed. The Zn-doped CsPbI₃ (Zn:CsPbI₃) QDs have been successfully synthesized employing ZnI₂ as the dopant to provide Zn²⁺ and extra I⁻. Theoretical calculations and experimental results demonstrate that the Zn:CsPbI₃ QDs show better thermodynamic stability and higher photoluminescence quantum yield (PLQY) compared to the pristine CsPbI₃ QDs. The doping of Zn in CsPbI₃ QDs increases the formation energy and Goldschmidt tolerance factor, thereby improving the thermodynamic stability. The additional I⁻ helps to reduce the V_I defects during the synthesis of CsPbI₃ QDs, resulting in the higher PLQY. More importantly, the synergistic effect of Zn²⁺ and I⁻ in CsPbI₃ QDs can prevent the iodine loss during the fabrication of CsPbI₃ QD film, inhibiting the formation of new V_I defect states in the construction of solar cells. Consequently, the anion/cation synergy strategy affords the CsPbI₃ quantum dot solar cells (QDSC) a power conversion efficiency over 16%, which is among the best efficiencies for perovskite QDSCs.     

24.64%-Efficiency MA-Free Perovskite Solar Cell with Voc of 1.19 V Enabled by a Hinge-Type Fluorine-Rich Complex

High density of defects at interface severely affects the performance of perovskite solar cells (PSCs). Herein, cobalt (II) hexafluoro-2,4-pentanedionat (CoFAc), a hinge-type fluorine-rich complex, is introduced onto the surface of formamidinium cesium lead iodide (FACsPbI₃) film to address the issues of perovskite/Spiro-OMeTAD interface. The existence of CoFAc passivates both organic cation and halide anion vacancies by establishing powerful hydrogen bonds with HC(NH₂)₂⁺ (FA⁺) and strong ionic bonds with Pb²⁺ in perovskite films. In addition, CoFAc serves as a connecting link to enhance interfacial hole-transport kinetics via interacting with Spiro-OMeTAD. Consequently, FACsPbI₃ PSCs with CoFAc modification display a champion power conversion efficiency (PCE) of 24.64% with a charming open-circuit voltage (V_OC) of 1.191 V, which is the record V_OC among all the reported organic-inorganic hybrid PSCs with TiO₂ as electron transport layer. Furthermore, CoFAc-modified devices exhibit an outstanding long-term stability, which can maintain 95% of their initial PCEs after exposure to ambient atmosphere for 1500 h without any encapsulation.     

Synergistic Crystallization Modulation and Defects passivation via Additive Engineering Stabilize Perovskite Films for Efficient Solar Cells

Organic-inorganic lead halide perovskite are promising photovoltaic materials, but their intrinsic defects and crystalline quality severely deteriorate the solar cells efficiency and stability. Herein, potassium 1,1,2,2,3,3-hexafluoroprop-ane-1,3-disulfonimide (KHFDF) is introduced into PbI₂ precursor solution to passivate various defects and improve the crystalline quality of perovskite films. It is found that KHFDF can inhibit PbI₂ crystallization, thus tuning the crystal orientation and growth of perovskite films. Furthermore, KHFDF with dual-functional sulfonyl group cannot only passivate grain boundaries (GBs), but also passivate the defects at GBs via strong interaction with undercoordinated Pb²⁺ and/or hydrogen bonding with FA⁺, while the K⁺ counter cations allow ionic interaction with undercoordinated I⁻. As a result, the KHFDF-modified films exhibit high quality with a larger grain size and a reduced trap-state density, thereby suppressing the trap-state nonradiative recombination. And the devices show a champion efficiency up to 24.15%, benefiting from a sharp enhancement of open-circuit voltage (V_oc) of 1.183 V and fill factor of 81.78%. In addition, due to the enhanced humidity tolerance and chemical structure stability, the devices exhibit excellent long-term humidity and thermal stability without encapsulation.     

Efficient Passivation Strategy on Sn Related Defects for High Performance All-Inorganic CsSnI3 Perovskite Solar Cells

Despite remarkable progress in hybrid perovskite solar cells (PSCs), the concern of toxic lead ions remains a major hurdle in the path towards PSC's commercialization; tin (Sn)-based PSCs outperform the reported Pb-free perovskites in terms of photovoltaic performance. However, it is of a particularly great challenge to develop effective passivation strategies to suppress Sn(II) induced defect densities and oxidation for attaining high-performance all-inorganic CsSnI₃ PSCs. Herein, a facile yet effective thioamides passivation strategy to modulate defect state density at surfaces and grain boundaries in CsSnI₃ perovskites is reported. The thiosemicarbazide (TSC) with SC N functional groups can make strong coordination interaction with charge defects, leading to enhanced electron cloud density around defects and increased vacancy formation energies. Importantly, the surface passivation can reduce the deep level trap state defect density originated from undercoordinated Sn²⁺ ion and Sn²⁺ oxidation, significantly restraining nonradiative recombination and elongating the carrier lifetime of TSC treated CsSnI₃ PSCs. The surface passivated all-inorganic CsSnI₃ PSCs based on an inverted configuration delivers a champion power conversion efficiency (PCE) of 8.20%, with a prolonged lifetime over 90% of initial PCE, after 500 h of continuous illumination. The present strategy sheds light on surface defect passivation for achieving highly efficient all-inorganic lead-free Sn-based PSCs.     

Modification of Energy Level Alignment for Boosting Carbon-Based CsPbI2Br Solar Cells with 14% Certified Efficiency

Hole transfer material (HTM)-free, carbon-based all-inorganic perovskite solar cells (C-PSCs) are promising alternatives to conventional organic–inorganic hybrid PSCs in addressing thermal and moisture instability issues. However, the energy level mismatch between the inorganic perovskite and carbon electrode coupled, together with the incapability of the carbon electrode to reflect incident light for reabsorption, limits the power conversion efficiency (PCE) of C-PSCs. To address these issues, herein, a new strategy of a hexyltrimethylammonium bromide (HTAB)-modified CsPbI₂Br perovskite surface is devised to reduce this energy offset from 0.70 to 0.32 eV and increase the built-in potential by 70 mV for the final devices. Additionally, a CsPbI₂Br perovskite film with a thickness of up to 800 nm is realized via a hot-flow-assisted spin coating approach in an ambient atmosphere with humidity of less than 80%. Reduced energy offset coupled with suppressed charge recombination and thick perovskite layer boosts the champion PCE of CsPbI₂Br C-PSCs to 14.3% (J_sc = 14.1 mA cm⁻², V_oc = 1.26 V, and fill factor = 0.806), and the average PCE to 13.9% under one sun illumination. A new certified efficiency record of 14.0% is obtained for HTM-free inorganic C-PSCs. Meanwhile, the moisture-resistant barrier from the alkyl chain in HTAB improves the stability of the final devices.     

δ‐CsPbI3 Intermediate Phase Growth Assisted Sequential Deposition Boosts Stable and High‐Efficiency Triple Cation Perovskite Solar Cells

Cs/FA/MA triple cation perovskite films have been well developed in the antisolvent dripping method, attributable to its outstanding photovoltaic and stability performances. However, a facile and effective strategy is still lacking for fabricating high‐quality large‐grain triple cation perovskite films via sequential deposition method a, which is one of the key technologies for high efficiency perovskite solar cells. To address this issue, a δ‐CsPbI₃ intermediate phase growth (CsPbI₃‐IPG) assisted sequential deposition method is demonstrated for the first time. The approach not only achieves incorporation of controllable cesium into (FAPbI₃)_1–x(MAPbBr₃)_x perovskite, but also enlarges the perovskite grains, manipulates the crystallization, modulates the bandgap, and improves the stability of final perovskite films. The photovoltaic performances of the devices based on these Cs/FA/MA perovskite films with various amounts of the δ‐CsPbI₃ intermediate phase are investigated systematically. Benefiting from moderate cesium incorporation and intermediate phase‐assisted grain growth, the optimized Cs/FA/MA perovskite solar cells exhibit a significantly improved power conversion efficiency and operational stability of unencapsulated devices. This facile strategy provides new insights into the compositional engineering of triple or quadruple cation perovskite materials with enlarged grains and superior stability via a sequential deposition method.     

Dual Passivation of Perovskite Defects for Light‐Emitting Diodes with External Quantum Efficiency Exceeding 20%

Solution‐processed metal halide perovskites (MHPs) have attracted much attention for applications in light‐emitting diodes (LEDs) due to their wide color gamut, high color purity, tunable emission wavelength, balanced electron/hole transportation, etc. Although MHPs are very tolerant to defects, the defects in solution‐processed perovskite LEDs (PeLEDs) still cause severe nonradiative recombination and device instability. Here, molecular design of additives for dual passivation of both lead and halide defects in perovskites is reported. A bi‐functional additive, 4‐fluorophenylmethylammonium‐trifluoroacetate (FPMATFA), is synthesized by using a simple solution process. The TFA anions and FPMA cations can bond with undercoordinated lead and halide ions, respectively, resulting in dual passivation of both lead and halide defects. In addition, the bulky FPMA group can constrain the grain growth of 3D perovskite, enhancing electron–hole capture rates and radiative recombination rates. As a result, high‐performance PeLEDs with a peak external quantum efficiency reaching 20.9% and emission wavelength at 694 nm are achieved using formamidinium‐cesium lead iodide‐bromide (FA_0.33Cs_0.67Pb(I_0.7Br_0.3)₃). Furthermore, the operational lifetime of PeLEDs is also greatly improved due to the low trap density in the perovskite film.     

Over 24% Efficient Poly(vinylidene fluoride) (PVDF)-Coordinated Perovskite Solar Cells with a Photovoltage up to 1.22 V

Recently, organic–inorganic metal halide perovskite solar cells (PSCs) have achieved rapid improvement, however, the efficiencies are still behind the Shockley–Queisser theory mainly due to their high energy loss (E_LOSS) in open-circuit voltage (V_OC). Due to the polycrystalline nature of the solution-prepared perovskite films, defects at the grain boundaries as the non-radiative recombination centers greatly affect the V_OC and limit the device efficiency. Herein, poly(vinylidene fluoride) (PVDF) is introduced as polymer-templates in the perovskite film, where the fluorine atoms in the PVDF network can form strong hydrogen-bonds with organic cations and coordinate bonds with Pb²⁺. The strong interaction between PVDF and perovksite enables slow crystal growth and efficient defect passivation, which effectively reduce non-radiation recombination and minimize E_LOSS of V_OC. PVDF-based PSCs achieve a champion efficiency of 24.21% with a excellent voltage of 1.22 V, which is one of the highest V_OC values reported for FAMAPb(I/Br)₃-based PSCs. Furthermore, the strong hydrophobic fluorine atoms in PVDF endow the device with excellent humidity stability, the unencapsulated solar cell maintain the initial efficiency of >90% for 2500 h under air ambient of ≈50% humid and a consistently high V_OC of 1.20 V.     

Preparation of Tortuous 3D γ‐CsPbI3 Films at Low Temperature by CaI2 as Dopant for Highly Efficient Perovskite Solar Cells

Inorganic cubic CsPbI₃ perovskite (α‐CsPbI₃) has been widely explored for perovskite solar cells (PSCs) due to its thermal stability and suitable bandgap of 1.73 eV. However, α‐CsPbI₃ usually requires high synthesis temperatures (>320 °C). Additionally, it usually undergoes phase transition to the nonperovskite structure phase (β‐CsPbI₃), which results in poor photoelectric performance in devices. In this study, it is first found that the tortuous 3D CsPbI₃ phase (γ‐CsPbI₃) can be prepared and used for PSCs by solution process without any additive at low temperature (60 °C). The γ‐CsPbI₃ exhibits suitable bandgap of 1.75 eV and favorable photoelectric properties. However, γ‐CsPbI₃ is a metastable phase and easily transforms into β‐CsPbI₃ in ambient moisture. In order to improve the stability of γ‐CsPbI₃, calcium ions (Ca²⁺) with a relatively small radius of 100 pm are used to partially substitute lead ions (119 pm). This research proves that Ca²⁺ can effectively improve the stability of the γ‐CsPbI₃ at room temperature. By optimizing the doping concentration of Ca²⁺ (CsPb_1?xCa_xI₃, x is from 0% to 2%), the Ca²⁺‐doped γ‐CsPbI₃ PSCs achieve a hysteresis‐free J–V curve and a maximum power conversion efficiency (PCE) of 9.20%.     

Low-Temperature Crystallized and Flexible 1D/3D Perovskite Heterostructure with Robust Flexibility and High EQE-Bandwidth Product

All-inorganic perovskite cesium lead triiodide (CsPbI₃) has attracted much attention among the perovskite family due to its excellent optoelectronic properties and chemical stability. However, the high-temperature crystallization process makes CsPbI₃ less compatible with commercially flexible substrates, limiting its application into flexible optoelectronics. Here, a cation of 1-(3-aminopropyl)-2pyrrolidinone (APP) is reported that can form 1D (APP)PbI₃ perovskite as templates, and significantly reduce the CsPbI₃ black-phase transition energy with a low annealing temperature of 75 °C, which further enables a flexible (APP)PbI₃/γ-CsPbI₃ (1D/3D) heterostructure photodetector on ITO/PET substrate. A high external quantum efficiency (EQE) greater than 2377% is observed along the orientated 1D/3D heterostructure. The high gain and low noise result in a high specific detectivity (D*) over 10¹² Jones under −0.6 V low bias. The optimized device structure brings a high EQE × bandwidth product of 119 kHz under a low driving bias. Due to the high toughness of orientated APP⁺ ions and the face-connected [PbI₃]⁻ chains structure as a strong energy absorber, the flexible photodetector also shows excellent phase stability and impressive flexibility, remaining >90% initial responsivity after over 20 000 times bending with potential flexible imaging application in harsh environments.     

Modifying Surface Termination of CsPbI3 Grain Boundaries by 2D Perovskite Layer for Efficient and Stable Photovoltaics

It is highly desirable for all-inorganic perovskite solar cells (PVSCs) to have reduced nonideal interfacial charge recombination in order to improve the performance. Although the construction of a 2D capping layer on 3D perovskite is an effective way to suppress interfacial nonradiative recombination, it is difficult to apply it to all-inorganic perovskites because of the resistance of Cs⁺ cesium ions in cation exchange reactions. To alleviate this problem, a simple approach using an ultra-thin 2D perovskite to terminate CsPbI₃ grain boundaries (GBs) without damaging the original 3D perovskite is developed. The 2D perovskite at the GBs not only enhances the charge-carrier extraction and transport but also effectively suppresses nonradiative recombination. In addition, because the 2D perovskite can prevent the moisture and oxygen from penetrating into the GBs and at the same time suppress the ion migration, the 2D terminated CsPbI₃ films exhibit significantly improved stability against humidity. Moreover, the devices without encapsulation can retain ≈81% of its initial power conversion efficiency (PCE) after being stored at 40 ± 5% relative humidity for 84 h. The 2D-based champion device exhibits a high PCE of 18.82% with a high open-circuit voltage of 1.16 V.     

A Large Bandgap Organic Salt Dopant for Sn-Based Perovskite Thin-Film Transistor

Metal halide perovskite optoelectronic devices have made significant progress over the past few years, but precise control of charge carrier density through doping is essential for optimizing these devices. In this study, the potential of using an organic salt, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, as a dopant for Sn-based perovskite devices, is explored. Under optimized conditions, the thin film transistors based on the doped 2D/3D perovskite PEAFASnI₃ demonstrate remarkable improvement in hole mobility, reaching 7.45 cm²V⁻¹s⁻¹ with a low subthreshold swing and the smallest sweep hysteresis (ΔV_hysteresis = 2.27 V) and exceptional bias stability with the lowest contact resistance (2.2 kΩ cm). The bulky chemical structure of the dopant prevents it from penetrating the perovskite lattice and also surface passivation against Sn oxidation due to its hydrophobic nature surface. This improvement is attributed to the bifunctional effect of the dopant, which simultaneously passivates defects and improves crystal orientation. These findings provide new insights into potential molecular dopants that can be used in metal halide perovskite devices.     

Dopant-Free Polymer HTM-Based CsPbI2Br Solar Cells with Efficiency Over 17% in Sunlight and 34% in Indoor Light

To abate the issue of moisture-assisted phase transition of CsPbI₂Br, caused by hygroscopic dopants used in the hole-transporting material (HTM), developing dopant-free HTMs is necessary. In this work, a new polymer, PDTDT, is developed as a dopant-free HTM for CsPbI₂Br solar cells, and the device performance and stability are systematically compared with cells employing dopant-free P3HT. CsPbI₂Br solar cells using PDTDT show an efficiency of 17.36% with V_OC of 1.42 V and FF of 81.29%, which is one of the highest values for CsPbI₂Br cells. Moreover, a record-high efficiency of 34.20% with V_OC of 1.14 V under 200 lux indoor light illumination and efficiency of 14.54% (certified efficiency of 13.86%) for a 1 cm² device under one sun are accomplished. Importantly, PDTDT shows superior/comparable device stability to P3HT, promising its potential to be an alternative to popular doped Spiro-OMeTAD and P3HT HTM.     

Solution-processed field-effect transistors based on polyfluorene –cesium lead halide nanocrystals composite films with small hysteresis of output and transfer characteristics

We have designed and investigated electrical and optical properties of solution-processed organic field-effect transistors (OFETs) based on conjugated polymer PFO and perovskite –cesium lead halide nanocrystals (CsPbI₃) composite films. It was shown that OFETs based on PFO:CsPbI₃ films exhibit current-voltage (I-V) characteristics of OFETs with dominant hole transport and saturation current behavior at temperatures 200–300 K. It was found that PFO:CsPbI₃ OFETs have a negligible hysteresis of output and transfer characteristics especially at temperatures below 250 K. The values of the hole mobility estimated from I-Vs of PFO:CsPbI₃ OFETs were found to be ∼2.4 10⁻¹ cm²/Vs and ∼1.9 10⁻¹ cm²/Vs in saturation and low fields regimes respectively at 300 K; the hole mobility dropped down to ∼6 10⁻³ cm²/Vs and 2.8 10⁻³ cm²/Vs respectively at 200 K, and then down to 5.5 10⁻⁵ cm²/Vs at 100 K (in low field regime), which is characteristic of hopping conduction. The effect of sensitivity to light and light-emitting effect were found under application of negative source-drain and gate pulse voltages to PFO:CsPbI₃ OFETs at 300 K. The mechanism of charge carrier transport in OFETs based on PFO:CsPbI₃ hybrid films is discussed.     

Surface Defects Management by In Situ Etching with Methanol for Efficient Inverted Inorganic Perovskite Solar Cells

Inorganic perovskite solar cells (IPSCs) have developed rapidly due to their good thermal stability and the bandgap suitable for perovskite/silicon tandem solar cells. However, the large open-circuit voltage (V_OC) deficit derived from the surface defects and the energy level structure mismatch impede the development of device performance, especially in the P-I-N structure IPSCs. Herein, an innovative in situ etching (ISE) treatment method is proposed to reduce surface defects through methanol without additional passivator. It is found that the perovskite films treated with methanol result in a slight excess of PbI₂ on the surface and inserted into the grain boundaries. Therefore, the successful decrease of surface defects by methanol and the passivation of grain boundary defects by PbI₂ greatly reduce the trap density of perovskite films. And the larger work function of PbI₂ contributes to the energy band of perovskite surface bending downward and forms gradient energy level alignment at the I/N interface, which accelerates extraction of charge carriers. As a result, the efficiency of CsPbI_2.85Br_0.15 inverted IPSC is enhanced from 16.00% to 19.34%, which is one of the mostly efficient IPSCs. This work provides an original idea without additional passivator to manage the defects of inorganic perovskite.     

Molecularly Tailored Surface Defect Modifier for Efficient and Stable Perovskite Solar Cells

Surface defects cause non-radiative charge recombination and reduce the photovoltaic performance of perovskite solar cells (PSCs), thus effective passivation of defects has become a crucial method for achieving efficient and stable devices. Organic ammonium halides have been widely used for perovskite surface passivation, due to their simple preparation, lattice matching with perovskite, and high defects passivation ability. Herein, a surface passivator 2,4,6-trimethylbenzenaminium iodide (TMBAI) is employed as the interfacial layer between the spiro-OMeTAD and perovskite layer to modify the surface defect states. It is found that TMBAI treatment suppresses the nonradiative charge carrier recombination, resulting in a 60 mV increase of the open-circuit voltage (V_oc) (from 1.11 to 1.17 V) and raises the fill factor from 76.3% to 80.3%. As a result, the TMBAI-based PSCs device demonstrates a power conversion efficiency (PCE) of 23.7%. Remarkably, PSCs with an aperture area of 1 square centimeter produce a PCE of 21.7% under standard AM1.5 G sunlight. The unencapsulated TMBAI-modified device retains 92.6% and 90.1% of the initial values after 1000 and 550 h under ambient conditions (humidity 55%–65%) and one-sun continuous illumination, respectively.     

Constructing All-Inorganic Perovskite/Fluoride Nanocomposites for Efficient and Ultra-Stable Perovskite Solar Cells

Organic-inorganic hybrid perovskite solar cells (PSCs) have rapidly developed over the past decade and have achieved the latest certified power conversion efficiency (PCE) up to 25.5%. However, unsatisfactory long-term operational stability for these hybrid PSCs remains a huge obstacle to further development and commercialization. Herein, a unique hetero-structured CsPbI₃/CaF₂ perovskite/fluoride nanocomposites (PFNCs) is fabricated via a newly developed facile two-step hetero-epitaxial growth strategy to deliver efficient and ultra-stable PSCs. After being incorporated into the crystal lattice of α-phase CsPbI₃ perovskite, the cubic-phase CaF₂ in the resultant CsPbI₃/CaF₂ PFNCs can not only passivate the intrinsic defects of CsPbI₃ perovskite itself but also effectively suppress the notorious ion migration in hybrid perovskite Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45 (CsFAMA) thin-films of PSCs. As such, the CsFAMA PSC devices based on CsPbI₃/CaF₂-deposited perovskite thin-film achieve a mean PCE of 20.45%, in sharp contrast to 19.33% of the control devices without deposition. Specifically, the CsPbI₃/CaF₂-deposited PSC retains 85% of its original PCE after 1000 h continuous operation at the maximum power point under AM 1.5G solar light, far better than those of the control and CsPbI₃-deposited PSCs with a device T₈₅ lifetime of 315 and 125 h, respectively.     

In-Situ Hot Oxygen Cleansing and Passivation for All-Inorganic Perovskite Solar Cells Deposited in Ambient to Breakthrough 19% Efficiency

All-inorganic perovskite CsPbI₃ has attracted extensive attention recently because of its excellent thermal and chemical stability. However, its photovoltaic performance is hindered by large energy losses (E_loss) due to the presence of point defects. In addition, hydroiodic acid (HI) is currently employed as a hydrolysis-derived precursor of intermediate compounds, which often leads to a small amount of organic residue, thus undermining its chemical stability. Herein, an in-situ hot oxygen cleansing with superior passivation (HOCP) for the triple halide-mixed CsPb(I_2.85Br_0.149Cl_0.001) perovskite solar cells (abbreviated as CsPbTh₃) deposited in an ambient atmosphere to reduce the E_loss to as low as 0.48 eV for the power conversion efficiency (PCE) to reach 19.65% is demonstrated. It is found that the hot oxygen treatment effectively removes the organic residues. Meanwhile, it passivates halide vacancies, hence reduces the trap states and nonradiative recombination losses within the perovskite layer. As a result, the PCE is increased significantly from 17.15% to 19.65% under 1 sun illumination with an open-circuit voltage enlarged to 1.23 from 1.14 V, which corresponds to an E_loss reduction from 0.57 to 0.48 eV. Also, the HOCP-treated devices exhibit better long-term stability. This insight should pave a way for decreasing nonradiative charge recombination losses for high-performance inorganic perovskite photoelectronics.