All-inorganic Perovskite Solar Cells Research Articles

CsPbI3 all-inorganic perovskite solar cells: Development status and theoretical prediction

In this paper, the crystal structure, physical properties, photoelectric conversion efficiency and large-area development of CsPbI3 all-inorganic perovskite solar cells are comprehensively analyzed. The research results of the material in photoelectric conversion efficiency, large-area development and preparation technology are summarized. In addition, through theoretical prediction and simulation, this study simulated a CsPbI3 all-inorganic perovskite solar cell with a photoelectric conversion efficiency of 28.29 %, which provided a theoretical basis for the preparation of high-performance devices.

Design tungsten oxides hole transport layers (HTLs) to modify the back interface in all-inorganic carbon-based CsPbBr3 solar cells

To enhance the inferior photovoltaic performance of all-inorganic carbon-based perovskite solar cells (C-PSCs) caused by inefficient charge extraction and transport processes of the CsPbBr3/carbon back interface, three types of tungsten oxides (WO3, WO2.72, WO2) are synthesized as low cost and stable hole transport layers (HTLs) to modify the back interface by tunning the energy level alignment. Among the three kinds of tungsten oxides, WO3 shows the best hole extraction and transport capability and the C-PSCs using WO3 HTL generates a power conversion efficiency (PCE) of 7.90% with a high open circuit voltage (Voc) of 1.307 V, indicating a great PCE enhancement of 43.9%, as compared with the device without HTL (5.49%). Meanwhile, WO2.72 and WO2 also are also proved to be qualified HTLs and the devices show PCE values of 7.57% and 6.24%, respectively. Importantly, WO3 and WO2.72 based device show excellent stabilities with PCE retention over 90% of the initial PCE values under ambient conditions for 60 days.

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.

Maximizing photovoltaic performance of all-inorganic perovskite CsSnI3-xBrx solar cells through bandgap grading and material design

In the modern era of technology, worldwide paradigms have been shifted toward the utilization of green energy. Sun energy is the most astonishing eco-friendly resource of energy and can be harnessed with the help of photovoltaic cells. Hybrid (Organic-Inorganic) perovskite solar cells (PSCs) are emerged with incredible photovoltaic (PV) performance. Nevertheless, a significant challenge lies in their lower stability under diverse environmental conditions. To deal with this challenge, all inorganic cesium-based PSC has been studied and analyzed, results improved stability in comparison to hybrid PSC. However, the noxious nature of lead is deleterious to the environment. So, this work primarily aimed, to study lead-free all inorganic tin-based perovskite compound CsSnI3-xBrx, as the main light absorber layer. Further, to elevate the PV performance of PSC, bandgap grading is performed on CsSnI3-xBrx by varying bromide concentration x from 0 to 3. Bandgap grading encourages the absorption of a wide range of the light spectrum, by modulating bandgap (Eg) / affinity(χ) through the distance of the CsSnI3-xBrx layer. Additionally, it enhances light-generated charge carrier separation and collection by end electrodes. In this work, two different strategies have been adopted, linear and parabolic. During linear grading, the impact of variation in x (0 to 3) has been analyzed over the thickness 50–––500 nm in 10 linear steps for CsSnI3-xBrx. The highest PCE fetched from linearly graded layered FTO / CeO2 / CsSnI3-xBrx / CFTS / Gold PSC is 21.68 %. Similarly, in the parabolic graded absorber layer, the influence of change in the bowing factor (0 to 1), has been analyzed relative to different values of x (0 to 3). With improvement in PV performance, the maximum PCE delivered by parabolic-graded PSC is 23.61 %. Additionally, this work extends to check the compatibility of distinct electron transport layers (ETLs) and hole transport layers (HTLs). Upon analysis, it has been found that the best PV performance was obtained while selecting SnO2 / PEDOT as ETL / HTL respectively.

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.

Over 12% efficient CsSnI3 perovskite solar cells enabled by surface post-treatment with bi-functional polar molecules

Eco-friendly all-inorganic tin halide perovskite compounds have drawn significant attention for photovoltaic applications. Nevertheless, the non-radiative recombination derived from the uncoordinated Sn2+ cations at surface and the electron extraction barrier between different functional layers significantly impair the performance of perovskite device. Here we for the first time show that thiophene derivative, 3-thiophenemethylammonium iodide, as an interface modifier between the CsSnI3 perovskite surface and electron transport layer, can passivate defects and reduce the electron extraction potential barrier. The molecules of 3-thiophenemethylammonium iodide can autonomously inter-connect with uncoordinated Sn2+via lone electron pairs of the donated π electrons in electronic-rich thiophene molecule. Moreover, such interface modifier lowers the electron extraction potential barrier at the perovskite/electron transport layer junction in which an interface dipole electric field form. Consequently, the optimized planar solar cell with a structure of ITO/PEDOT:PSS/CsSnI3/ICBA/BCP/Ag, exhibited a power conversion efficiency of 12.05 % under AM 1.5G illumination condition. To the best of our knowledge, this is the highest efficiency for fully inorganic CsSnI3-based devices reported so far. This study represents an innovative approach to realize high-efficiency all-inorganic CsSnI3 perovskite solar cells.

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.

Multifunctional Interface Modification Enables Efficient and Stable HTL-Free Carbon-Electroded CsPbI2Br Perovskite Solar Cells.

In recent years, hole transport layer-free all-inorganic CsPbI2Br carbon-electroded perovskite solar cells (C-PSCs) have garnered significant attention due to a trade-off between stability and photovoltaic performance. However, there are inevitably many defects generated at the surfaces or grain boundaries of CsPbI2Br perovskite films, which will serve as carrier non-radiative recombination centers, and CsPbI2Br perovskite films are sensitive to water molecules to degrade, together with energy level mismatch between CsPbI2Br perovskite and carbon electrodes. Herein, 1-benzyl-3-methylimidazolium hexafluorophosphate (1-B-3-MIMPF6), an imidazolium-based ionic liquid simultaneously containing benzene ring and fluorine atoms, was introduced for the modification of the perovskite/carbon interface. The results showed that it could effectively reduce defects, enhance carrier transfer, mitigate carrier non-radiative recombination, facilitate energy alignment, and block moisture intrusion. Therefore, the photovoltaic performance of the modified PSCs with ITO/SnO2/CsPbI2Br/1-B-3-MIMPF6/carbon architecture has been boosted with a champion power conversion efficiency (PCE) of 13.47 %, open circuit voltage of 1.20 V, short circuit current density of 14.69 mA/cm2, and fill factor of 76 %. Moreover, the unencapsulated modified devices exhibited an improved stability and the PCE maintained 78 % of their initial PCE after 24 h storage at room temperature in a 30 %-35 % humidity environment, whereas that of the pristine devices dropped to almost zero.

Doping with KBr to Achieve High-Performance CsPbBr3 Semitransparent Perovskite Solar Cells.

Wide-bandgap semitransparent perovskite photovoltaics are emerging as one of the ideal candidates for building-integrated photovoltaics (BIPV). However, surface defects in inorganic CsPbBr3 perovskite prepared by vapor deposition severely limit the optoelectronic performance of perovskite solar cells. To address this issue, a strategy of doping a trace amount of KBr into perovskite by vapor deposition is adopted, effectively improving the quality of the film, reducing surface defect concentration, and enhancing the transportation and extraction of charge carriers. Simultaneously, fully physical vapor deposition technology is employed to fabricate perovskite solar cells with an average visible light transmittance of 44%. These devices exhibited an ultrahigh open-circuit voltage of 1.55 V and a superior power conversion efficiency (PCE) of 7.28%, demonstrating excellent moisture and heat resistance. Moreover, the corresponding 5 cm × 5 cm modules achieve a PCE of 5.35% with great thermal insulation capability. This work provides an approach for fabricating highly efficient all-inorganic perovskite solar cells with high average visible light transmittance, demonstrating new insights into their application in building-integrated photovoltaics.

BMP]+[BF4]--Modified CsPbI1.2Br1.8 Solar Cells with Improved Efficiency and Suppressed Photoinduced Phase Segregation.

With the rapid progress in a power conversion efficiency reaching up to 26.1%, which is among the highest efficiency for single-junction solar cells, organic-inorganic hybrid perovskite solar cells have become a research focus in photovoltaic technology all over the world, while the instability of these perovskite solar cells, due to the decomposition of its unstable organic components, has restricted the development of all-inorganic perovskite solar cells. In recent years, Br-mixed halogen all-inorganic perovskites (CsPbI3-xBrx) have aroused great interests due to their ability to balance the band gap and phase stability of pure CsPbX3. However, the photoinduced phase segregation in lead mixed halide perovskites is still a big burden on their practical industrial production and commercialization. Here, we demonstrate inhibited photoinduced phase segregation all-inorganic CsPbI1.2Br1.8 films and their corresponding perovskite solar cells by incorporating a 1-butyl-1-methylpiperidinium tetrafluoroborate ([BMP]+[BF4]-) compound into the CsPbI1.2Br1.8 films. Then, its effect on the perovskite films and the corresponding hole transport layer-free CsPbI1.2Br1.8 solar cells with carbon electrodes under light is investigated. With a prolonged time added to the reduced phase segregation terminal, this additive shows an inhibitory effect on the photoinduced phase segregation phenomenon for perovskite films and devices with enhanced cell efficiency. Our study reveals an efficient and simple route that suppresses photoinduced phase segregation in cesium lead mixed halide perovskite solar cells with enhanced efficiency.

All-Inorganic Perovskite Solar Cells: Defect Regulation and Emerging Applications in Extreme Environments.

All-inorganic perovskite solar cells (PSCs), such as CsPbX3 , have garnered considerable attention recently, as they exhibit superior thermodynamic and optoelectronic stabilities compared to the organic-inorganic hybrid PSCs. However, the power conversion efficiency (PCE) of CsPbX3 PSCs is generally lower than that of organic-inorganic hybrid PSCs, as they contain higher defect densities at the interface and within the perovskite light-absorbing layers, resulting in higher non-radiative recombination and voltage loss. Consequently, defect regulation has been adopted as an important strategy to improve device performance and stability. This review aims to comprehensively summarize recent progresses on the defect regulation in CsPbX3 PSCs, as well as their cutting-edge applications in extreme scenarios. The underlying fundamental mechanisms leading to the defect formation in the crystal structure of CsPbX3 PSCs are firstly discussed, and an overview of literature-adopted defect regulation strategies in the context of interface, internal, and surface engineering is provided. Cutting-edge applications of CsPbX3 PSCs in extreme environments such as outer space and underwater situations are highlighted. Finally, a summary and outlook are presented on future directions for achieving higher efficiencies and superior stability in CsPbX3 PSCs.

Synergizing experimental and theoretical insights: Unveiling the solar potential of La2NiMnO6 double perovskite for enhanced efficiency and sustainability in photovoltaics

Amidst the escalating demand for sustainable energy solutions, this research delves into the competence of double perovskite oxide La2NiMnO6 as a solar cell luminary. Addressing material synthesis, structural intricacies, and device construction, the study responds to the limitations of labour-intensive first-generation Si solar cells along with the toxicity of lead attributed perovskite solar cells, steering towards a revolutionary era. La2NiMnO6 distinctive attributes a formidable dielectric constant, positioning it as a beacon in solar energy. Crafted via sol gel citrate alchemy, its structural, optical, and electronic intricacies were meticulously explored. Experimental insights into the fabrication process, employing optimised spray pyrolysis layers, enrich the narrative. Structural analyses confirm La2NiMnO6 prowess, while optical studies unveil its visible spectrum absorbance. Simulations and the experimental J-V curve show PCEs of 10% and 4.5 %, solidifying the La2NiMnO6 stance in the all-inorganic perovskite solar cell realm. This study propels the evolution of photovoltaic technology, laying pathways for sustainable energy alternatives and setting new benchmarks.

Numerical simulation and performance optimization of all-inorganic CsGeI3 perovskite solar cells with stacked ETLs/C60 by SCAPS device simulation

Perovskite solar cells, particularly those featuring CsGeI3 as the absorption layer, are distinguished by their non-toxicity and inherent stability. In this work, to optimize the interface contact of the cells, enhance their built-in electric field, and consequently augment the power conversion efficiency, a C60 layer was incorporated into the electronic transport layer. This incorporation led to the formation of a novel dual-electron transport layer structure. Employing SCAPS-1D simulation software, a range of electron and hole transport layer combinations was explored. The optimal configuration was determined to be FTO/SnO2/C60/IDL1/CsGeI3/IDL2/Cu2O/Au. The absorption layer's thickness, doping concentration, defect density, and bandgap were optimized. Furthermore, an investigation was conducted on the performance implications arising from alterations in the dual electron conduction layer SnO2/C60's thickness, bandgap, and doping concentration. Concurrently, adjustments were made to refine the defect density in the interface defect layer, and an investigation was carried out to determine the optimal operational temperature. These endeavors culminated in the achievement of an impressive 30.34% optimal power conversion efficiency, representing a significant 54.25% enhancement over the pre-optimization efficiency of 19.67%. This work stands as a valuable reference for subsequent investigations into the dual electron transport layer structure in Ge-based perovskite solar cells.

Mathematical Modeling and Optimization of Highly Efficient Nontoxic All-Inorganic CsSnGeI3-Based Perovskite Solar Cells with Oxide and Kesterite Charge Transport Layers.

Despite exceptional optoelectronic properties and rapidly increasing efficiency of perovskite solar cells (PSCs), the issues of toxicity and device instability have hampered the commercialization of this renewable energy technology. Lead (Pb) being the main culprit creates major environmental risks and therefore must be replaced with a nontoxic material such as tin (Sn), germanium (Ge), etc. Moreover, replacing organic cations in the perovskite's ABX3 structure with inorganic ones like cesium (Cs) helps aid the stability issues. This study uses six different kesterite-based hole transport layers (HTLs) and three different metal oxide-based electron transport layers (ETLs) to numerically simulate and optimize all-inorganic CsSnGeI3 PSCs. Metal oxide ETLs are used in this study due to their large band gap, while kesterite HTLs are used due to their excellent conductive properties. All of the simulations are performed under standard testing conditions. A total of 18 novel planar (n-i-p) PSCs are modeled by the combination of various charge transport layers (CTLs), and the device optimization was done to enhance the power conversion efficiencies (PCEs) of the PSCs. Furthermore, the effect of CTLs on the energy band alignment, electric field, quantum efficiency, light absorption, and recombination rate is analyzed. Additionally, a detailed analysis of the impact of defect density (Nt), interface defects (ETL/Perv, Perv/HTL), temperature, and work function on the functionality of 18 different CsSnGeI3-based PSCs is conducted. The simulation findings demonstrate that SnO2/CsSnGeI3/CNTS is the most efficient optimized PSC among all of the simulated structures, with a PCE of 27.33%, Jsc of 28.04 mA/cm2, FF of 85%, and Voc of 1.14 V.

A theoretical study of all-inorganic perovskite solar cells: Computational modeling of the CsPbI[formula omitted]/RbGeI[formula omitted] bilayer absorber structure

All-inorganic perovskite solar cells (AI-PSCs) have garnered significant attention in the perovskite community due to their stability and efficient photogeneration and absorption capabilities. Despite the toxicity associated with all-inorganic CsPbI3 perovskites containing lead (Pb), its presence remains crucial for achieving excellent photovoltaic properties. However, the imperative shift towards AI-PSCs using less toxic materials with suitable photovoltaic properties is imperative. The incorporation of a double perovskite absorber layer allows for broadening the absorption spectrum of PSCs and enhancing cell stability. In this study, we propose a novel AI-PSC structure with CsPbI3 as the top absorber with a wide bandgap of 1.69 eV and a lead-free RbGeI3 perovskite as the bottom absorber layer with a low bandgap of 1.31 eV. Utilizing numerical simulations with the SCAPS-1D simulator, we analyze the photovoltaic parameters of AI-PSCs with single and double absorber layers. Our investigations reveal that a double absorber layer structure, comprising CsPbI3 and RbGeI3 materials, outperforms a single-junction PSC based on CsPbI3. By optimizing critical device parameters, we achieved an impressive efficiency of 31.91% in an AI-PSC device with a CsPbI3(0.6 μm)/RbGeI3(2 μm) bilayer configuration. This study positions lead-free RbGeI3 perovskite as a promising partner for CsPbI3, offering a potential pathway for the development of highly efficient AI-PSCs.

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.

Integration of SWCNT and WO3 for efficient charge extraction in all-inorganic perovskite solar cells

The construction of efficient interfacial charge transfer and extraction plays an essential role in improving the photovoltaic performance of perovskite solar cells (PSCs). Herein, the single-walled carbon nanotube (SWCNT) and WO3 are integrated as a robust hole extractor for all-inorganic CsPbBr3 PSCs. The introduction of SWCNT with high carrier transport behavior and numerous oxygen-containing edge groups not only promotes the hole transport from CsPbBr3 film to carbon back electrode, but also passivates the metal ion defect states within the CsPbBr3 film. The further integration of WO3 hole transport materials compensates for the energy level gap between the perovskite film and the carbon electrode to decrease interfacial energy loss and boosts hole extraction. Benefiting from the collaborative promotion of charge transport and extraction by SWCNT and WO3, the tailored CsPbBr3 PSCs without encapsulation achieve a champion power conversion efficiency of 10.47 % and a long-term stability with 91.3 % retention of the initial efficiency under high temperature and humidity conditions for 800 h.

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.

Recent progress in all-inorganic tin-based perovskite solar cells: a review

Recent progress in all-inorganic tin-based perovskite solar cells: a review

Back interface engineering by 2D layered N–Ti3C2 in low-cost carbon based all-inorganic hole transport layer free perovskite solar cells

The mismatched energy level alignments, back interface defects in the perovskite/carbon back interface, as well as low conductivity of carbon counter electrode are the primary factors for the low photovoltaic behavior of all-inorganic hole transport layer (HTL)-free perovskite solar cells (C–PSCs) using carbon counter electrode-based. Herein, 2D layered Ti3C2 and N–Ti3C2 are proposed to form Ti3C2@carbon and N–Ti3C2@carbon counter electrodes for modifying the perovskite/carbon back interface. First, the appropriate work function of Ti3C2 can optimize the energy level alignments. Second, nitrogen doping can enhance the conductivity of Ti3C2 which can lower the total resistance of the device. Third, the specific 2D layered structure Ti3C2 and N–Ti3C2 can reduce back interface defects. Therefore, the perovskite/carbon back interface shows improved charge extraction and transport capabilities disclosed by photoluminescence measurements. Consequently, the power conversion efficiencies (PCE) of the C–PSCs are enhanced to 7.56 % from 5.94 % by using Ti3C2@carbon counter electrode, and further to 8.91 % by using N–Ti3C2 @carbon counter electrode, indicating remarkable PCE improvements of 27.3 % and 50.0 %. Moreover, the Ti3C2@carbon and N–Ti3C2@carbon-based C–PSCs show remarkable stabilities under ambient conditions for 30 days. This work is expected to provide a feasible path to optimize the back interface of the all-inorganic C–PSCs.