Locking Surface Dimensionality for Endurable Interface in Perovskite Photovoltaics

Abstract

ABSTRACT

Surface passivation with organic ammoniums improves perovskite solar cell performance by forming 2D/quasi‐2D structures or adsorbing onto surfaces. However, complexity from mixed phases can trigger phase transitions, compromising stability. The control of surface dimensionality after organic ammonium passivation presents significant importance to device stability. In this study, we developed a poly‐fluorination strategy for surface treatment in perovskite solar cells, which enabled a high and durable interfacial phase purity after surface passivation. The locked surface dimensionality of perovskite was achieved through robust interaction between the poly‐fluorinated ammoniums and the perovskite surface, along with the steric hindrance imparted by fluorine atoms, reducing its reactivity and penetration capabilities. The high hydrophobicity of the poly‐fluorinated surface also aids in moisture resistance of the perovskite layer. The champion device achieved a power conversion efficiency (PCE) of 25.2% with certified 24.6%, with 90% of its initial PCE retained after approximately 1200 h under continuous 1‐sun illumination, and over 14,400 h storage stability and superior stability under high‐temperature operation.

Introduction

Metal halide perovskite (ABX₃, where A is usually a monovalent organic cation, B is a divalent cation, and X is a halide anion) has emerged as a prominent contender in the field of next-generation photovoltaic materials. Over the past decades, perovskite solar cells (PSCs) have witnessed remarkable progress, with their power conversion efficiency (PCE) soaring to an impressive high value [1, 2]. Despite the promising prospects, such as ease-of-fabrication and low manufacturing cost, the commercialization of PSCs still faces challenges in terms of long-term stability, acting as major deterrents in their widespread adoption [3]. Surface modification utilizing organic ammonium has been widely adopted as an effective approach to improve both the PCE and stability of devices. Organic ammonium salts possess –NH₃⁺ functional groups that can interact with the defective surface of polycrystalline perovskite thin film [4–8]. They can react with the excess lead iodide (PbI₂) on the perovskite surface, leading to the formation of two-dimensional (2D) [9–13], quasi-2D [14–17] phases, or a mixture of such phases on the surface. The formation of such a thin layer atop always aids in reducing the nonradiative recombination of charge carriers at the interface. The superior resistance of such phases to moisture and oxygen also helps improve the film stability [18, 19]. Alternatively, in some circumstances, these organic ammoniums can attach to the perovskite surface through coordination bonding [20], electrostatic interactions [13, 21], or physical absorption [22, 23] at the defective perovskite surface without forming 2D phases. Such surface molecular absorption is enabled by the isovalent charge and a comparable size of their –NH₃⁺ anchoring unit to the A-site cations in the bulk film. Both surface passivation mechanisms, whether resulting in the formation of 2D phases or not, have been reported to benefit the device performance on a comparable level [17]. However, controlling the formation of surface structures after depositing organic ammonium-based passivators presents a significant challenge. The deposition of these passivators frequently results in the in-situ formation of mixed structures, including molecular absorption, and 2D and quasi-2D perovskite phases presented by the formula (R-NH₃)₂A_n-1B_nX_3n+1, where n is the number of octahedral layers; different n values correspond to varied perovskite phase dimensionality, with n = 1 for 2D, and n > 1 for quasi-2D [15]. The absorption of the organic ammonium without forming a complete 2D structure can be loosely described as the case of n = 0. The difficulty in controlling such intricate surface reactions can be reflected by the fact that slight variations in the deposition processes of the organic ammoniums with even the same molecular structure can lead to significantly different surface structures [4, 15]. Such a phenomenon is likely due to the similarly low formation energies of these phases on the perovskite interface [24]. This always induces the evolution of surface phases during the long-term operation of the devices, deteriorating the device longevity of PSCs [15, 25–29]. This study addressed the problem of uncontrollable perovskite surface dimensionality caused by introducing a poly-fluorination strategy. We replaced the hydrogen atoms on the conventionally used alkyl chain-based organic ammoniums with fluorine atoms, which successfully locked the perovskite surface dimensionality taking advantage of the unique surface interaction capability and the steric effects of this highly fluorinated structure. The resultant endurable interface facilitates the elongation of device longevity.

Results and Discussion

Derived from the widely used surface posttreatment material butylamine hydroiodide (BAI), we substituted the seven hydrogen atoms in the alkyl chain with fluorine atoms, resulting in 2,2,3,3,4,4,4-heptafluoro butylamine hydroiodide (7FBAI) (Figure 1A). The molecular structure of 7FBAI was confirmed via the ¹H-NMR spectroscopy in Supporting Information S1: Figure S1. We spin-coated BAI and 7FBAI respectively on perovskite films, followed by annealing at 100°C for 1 min. We performed X-ray diffraction (XRD) on films treated with BAI or 7FBAI. In Figure 1B, we show the zoomed-in XRD patterns over a diffraction angle (2θ) range of 2°–10°. For the BAI-treated film, low-diffraction-angle features at 4.5° and 9.0° correspond to the first- and second-order diffraction peak of n = 2 phase, respectively [21]. The diffraction signal located at 6.4° corresponds to the n = 1 phase of perovskite. The results confirm the presence of multiple surface structures on the film. For the 7FBAI-treated film, the absence of Bragg diffraction signals at low diffraction angles suggests that 7FBAI treatment leads to a high phase purity of 3D only throughout the film. A complete diffraction pattern from 2° to 50° is available in Figure 1C; the diffraction peaks at 14.1° and 28.4° correspond to the characteristic (001) and (002) crystal planes of the α-phase perovskite, respectively, showing that the treatment of either BAI or 7FBAI does not induce obvious change in crystal orientation of the 3D phase of perovskite.

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We used scanning electron microscopy (SEM) to evaluate the perovskite film morphology. Compared with the untreated film in Supporting Information S1: Figure S2, BAI- and 7FBAI-treated films both showed enlarged grain sizes to a similar extent (Figure 1D,E), which is also supported by the atomic force microscopy (AFM) results in Supporting Information S1: Figure S3A,B. We used conductive AFM (C-AFM) to study the electronic properties of films after treating them with different passivators (Supporting Information S1: Figure S3C,D). The BAI- and 7FBAI-treated films demonstrated a similar averaging surface current signal of ~21.8 and ~22.3 pA, respectively, suggesting that both treatments led to slightly enhanced surface conductivity. Supporting Information S1: Figure S3E,F presents the statistical results of the surface current signals. 7FBAI treatment results in a full width at half maxima (FWHM) of 0.48, which is similar to that of the 0.54 after BAI treatment, indicating a similarly uniform conductivity throughout the films. We used UV-visible (UV-vis) absorption spectroscopy to examine the bandgaps of perovskite films treated with BAI or 7FBAI (Supporting Information S1: Figure S4). The absorption threshold for the 7FBAI sample was almost the same as the BAI-treated one, which indicates that the poly-fluorination strategy does not significantly alter the bandgap of the perovskite films. We then used photoluminescence (PL) and time-resolved PL (TRPL) measurements to elucidate the charge carrier dynamics of the perovskite films. The 7FBAI-treated film exhibited an enhanced PL intensity compared with the BAI-treated one, which suggested the reduced defect density in the 7FBAI sample (Figure 1F). The TRPL response in Figure 1G shows that, compared with BAI, 7FBAI treatment yielded an extended PL lifetime from 2.5 to 3.6 μs, which indicated 7FBAI being more effective in suppressing carrier recombination and reducing lower defect density than BAI. PL mapping (Supporting Information S1: Figure S5) showed a higher averaging PL intensity in the 7FBAI-treated film than that of the BAI-treated sample, which aligns well with the results from the PL measurements. The PL intensity of 7FBAI showed a narrower uniform distribution compared with that of the BAI-treated film, which suggests that 7FBAI is more evenly distributed than BAI on the perovskite surface and interacted with the surface defects. This observation is also consistent with the C-AFM results.

We conducted aging tests on these perovskite films under various conditions to evaluate their durability. Figure 2A,B exhibits the XRD patterns of the perovskite films with BAI and 7FBAI subjected to 1-sun light soaking for different durations, that is, 0, 3, and 7 days, respectively. The signals from n = 1 and n = 2 phases from the fresh film, as discussed in Figure 1B, suggest the inherent low formation energy of these phases, which impede the control of surface composition from the outset. This leads to an increased disorder in surface structure and compromised film stability when the films are exposed to external stimuli. With increasing illumination duration, the BAI-treated film showed enhanced diffraction signals from the quasi-2D phase (n = 2, 2θ = 4.5°), while signals from the n = 1 phase (2θ = 6.4°) diminished. The change in the relative intensity of different phases over time indicates the surface phase transitions during the illumination. This could be attributed to the movement of the butylammonium cation, demonstrating the failure of BAI in maintaining surface dimensionality over time. In contrast, the XRD patterns of 7FBAI-treated films maintained imperceptible signals from low-dimensional phases with extended illumination, which indicates a stable surface phase structure locked by the 7FBAI. Figure 2C,D shows the XRD patterns of BAI and 7FBAI-treated films, respectively, after annealing at different temperatures room temperature (RT), 85, 100, and 125°C) for 10 min. For BAI-treated film, diffraction signals corresponding to low-dimensional phases (n = 1 at 2θ = 6.4° and n = 2 at 2θ = 4.5°) were observed across films annealed at all four temperatures. The increase in the annealing temperature led to a decrease in peak intensity of n = 1 phase, while the peak intensity of n = 2 phase increased. This intensity of that phase n = 1 is more readily transformed into the n = 2 phase under elevated temperature. We introduce the value of activation energy to demonstrate from a kinetic perspective that the 2D phase transition on the surface of 3D/2D perovskites can occur rapidly; according to the Arrhenius equation [30], the activation energy for phase transition from n = 1 to n = 2 can be estimated to be 0.13 eV, as shown in Supporting Information S1: Figure S6. This estimated value is much lower than the conventional 0.42–4.17 eV activation energy in most cases [31]. The low activation energy results in the easy transition from n = 1 to n = 2 phase and leads to the coexistence of multiple phases with varied n values. Contrastingly, no peaks were observed for the 7FBAI sample throughout the aging tests under different annealing temperatures, confirming the successfully retained surface dimensionality.

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To gain mechanistic insights into how 7FBAI treatment enabled the locking of surface dimensionality of perovskite, we conducted X-ray photoelectron spectroscopy (XPS) on perovskite films treated with 7FBAI or BAI. As shown in Supporting Information S1: Figure S7, the BAI-treated sample did not show signals from fluorine atoms, while the presence of the fluorine (F 1s) peak at 687.5 eV verifies the successful deposition of 7FBAI on the perovskite surface. In Figure 3A, the pristine film exhibited two peaks at 137.9 and 142.8 eV, which correspond to the Pb 4f_7/2 and Pb 4f_5/2, respectively. For the 7FBAI-treated film, these peaks shifted to slightly higher binding energies of 138.2 and 143.1 eV, respectively, whereas the BAI-treated film showed smaller peak shifts. These results suggest that the interaction between the ammonium group of 7FBAI and the surface Pb of perovskite is stronger than that between BAI and the latter. We attribute this to the strong electronegativity of the fluorine atoms in 7FBAI, which made the electron cloud within the molecules shift away from the ammonium head group. This made the –NH₃⁺ groups in 7FBAI more positively charged, strengthening their binding with the negatively charged PbI₆²⁻ terminated perovskite surface. As a result, the molecular anchoring capability on the perovskite surface is enhanced. This is further verified by the electrostatic potential (ESP, φ) of 7FBAI and BAI obtained by the Gauss simulation (Figure 3B). The maximum ESP (φ_max) in the molecule, which is on the ammonium head group, is increased from 152 kcal/mol for BAI to 157 kcal/mol for 7FBAI. This means the electrons are redistributed in 7FBAI due to the electron-withdrawing effect induced by the fluorine atoms. Compared with the BAI molecules, the electrons deviate away from the ammonium head group in 7FBAI, resulting in more positively charged –NH₃⁺ groups bonding strongly with the negatively charged surface defects. We used Fourier transform infrared (FTIR) spectroscopy to gain a further understanding of the interaction between fluorine atoms and the perovskite framework. The C–F bond in pure 7FBAI showed typical stretching vibration modes at 897 and 720 cm^–1, which is shifted to 903 and 724 cm^–1, respectively, upon binding to FAI (Figure 3C). The absence of obvious vibration absorption in the C–F bond peak position for the pure FAI sample indicates the accuracy of the FTIR results. The upward shift of the C–F bond stretching vibration frequency could result from the electrons being biased toward the C–F bond when a hydrogen bond was formed between FA⁺ and the fluorine atoms, as depicted in Figure 3D. To confirm this speculation, we mixed BAI or 7FBAI with FAI to further compare the interaction between FAI and BAI or 7FBAI (Figure 3E and Supporting Information S1: Figure S8). The N–H bond of FAI in perovskite precursor showed typical stretching modes at 3342 and 1601 cm^–1, respectively. In the case of BAI, N–H bond peak positions showed negligible peak shift, suggesting weak interaction with FAI. When the hydrogen atoms were replaced by fluorine atoms, the vibration frequency of N–H bonds in 7FBAI shifted to 3336 and 1598 cm^–1, respectively. This indicates the molecular interaction between the N–H bonds in FAI and 7FBAI, which can be attributed to the formation of hydrogen bonds between FA⁺ and fluorine atoms. We then resorted to solution-state proton nuclear magnetic resonance (¹H NMR) spectroscopy to resolve the hydrogen bonding interaction between FAI and 7FBAI (Figure 3F). The peaks at 8.99 and 8.66 ppm can be assigned to the hydrogen attached to nitrogen atoms in FAI. There is no significant peak shift after introducing BAI, indicating a weak molecular interaction. On the contrary, the introduction of 7FBAI into FAI results in a peak position shift to 9.09 and 8.82 ppm, respectively, which can be attributed to the weakened electron shielding effect as hydrogen bonds form between FA⁺ and fluorine atoms. The hydrogen bond, along with the larger volume of F atoms than H atoms, could also introduce extra steric hindrance to the 7FBAI molecules to lower their reactivity and, thus, block the penetration of 7FBAI toward the perovskite bulk phase. In comparison to the BAI sample, the significantly increased contact angle of 7FBAI suggests a reduced interfacial energy, originating from the fluorine atoms being exposed on top. Such reduced interfacial energy could lead to a more stable interface (Supporting Information S1: Figure S9). Apart from the locked surface dimensionality, the hydrophobic nature of fluorine also facilitates such an endurable interface by protecting the perovskite active layer from environmental moisture. As summarized in Figure 3G, the highly reactive BAI moves from the perovskite surface, which leads to the surface structure evolution and the coexistence of multiple surface structures. In comparison, the strong interaction between 7FBAI and the perovskite surface, along with the steric hindrance and low reactivity, potentially makes 7FBAI be easily fixed on the perovskite surface, locking the surface dimensionality for an endurable interface (Figure 3H).

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We assessed fabricated PSCs (ITO/SnO₂/FA_0.95Cs_0.05PbI₃/spiro-OMeTAD/Ag) using the spin coating method. Figure 4A shows the J-V characteristics under simulated AM 1.5 G illumination of the champion PSCs obtained with the respective molecule, with photovoltaic parameters summarized in the inset.

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The best-performing BAI-based device showed a PCE of 24.0%, with an open-circuit voltage (V_OC) of 1.17 V, a short-circuit current (J_SC) of 25.7 mA cm^–2, and a fill factor (FF) of 79.8% (Figure 4A). Replacing the BAI passivation layer with 7FBAI yielded a considerably improved PCE up to 25.2% (certified 24.6% with an active area of 9.3 mm², see the certificate in Supporting Information S1: Figure S10), with a V_OC of 1.20 V, a J_SC of 25.9 mA cm⁻², and an FF of 81.1%. The external quantum efficiency (EQE) measurements indicate that the target devices exhibit the same photon response across the entire spectra as the control devices, which match the measured short-circuit current density values (Supporting Information S1: Figure S11). Statistical photovoltaic parameters summarized in the box plots in Supporting Information S1: Figure S12 confirmed good reproducibility of the PCE improvement with 7FBAI. The maximum power point tracking of devices passivated with BAI or 7FBAI is shown in Figure 4B, where the 7FBAI-treated device exhibited a higher PCE with a more stable output than the BAI-treated devices within 2-min maximum power point tracking. The improved performance of 7FBAI-based devices could be attributed to the reduced carrier recombination and faster charge extraction. The relationship of V_OC versus the logarithm of different illumination intensities was performed to understand the carrier transport and recombination in the PSCs (Figure 4C). Introducing the ideality factor n_ID as a pre-factor [32] we find that ${\mathit{eV}}_{\mathit{OC}}=E_g-n_{\mathit{ID}}{k}_{B}T\ln \frac{I_0}{I},$where E_g is the bandgap, T is the temperature, k_B is the Boltzmann constant, and I₀ is the reverse saturation current. Measurement of V_OC as a function of light intensity for solar cells with different treatments yields ideality factors of 1.59 for BAI and 1.32 for 7FBAI. The ideality factor of the 7FBAI-treated device was determined to be closer to 1 compared with the BAI-treated device, indicating reduced non-radiative charge recombination. The suggested reduction in non-radiative charge recombination by ideality factor also explains the improvement in V_OC for 7FBAI-based devices. The difference in charge recombination was also reflected in the reverse saturation current as revealed by dark J-V measurements. Figure 4D shows the comparison of the dark J-V curves of 7FBAI- and BAI-treated devices. The 7FBAI-based device featured a lower reverse saturation current, indicative of reduced interfacial trap states, and thus suppressed non-radiative charge recombination. The reduced carrier recombination of the 7FBAI-based device is also evidenced by the transient photovoltage (TPV) results under open-circuit conditions (Supporting Information S1: Figure S13A). A slower TPV decay for a 7FBAI-based device suggests a substantially longer charge-recombination lifetime, which is consistent with the TRPL measurement. This indicates a lower defect concentration and hence enhanced electronic property in the 7FBAI-incorporated perovskite film, consistent with the higher V_OC of the corresponding devices. Meanwhile, transient photocurrent (TPC) decay under the short-circuit condition was conducted to investigate the influence of 7FBAI on the charge transfer in the devices (Supporting Information S1: Figure S13B). A faster transient photocurrent decay suggests charge transfer lifetime in the 7FBAI-containing device, without affecting the perovskite band structure. The enhanced charge transfer might have resulted from the reduced interfacial defects and the better film quality of 7FBAI-based films, consistent with the higher J_SC and FF.

The changes in PCEs of the PSCs were tracked over time under one sun illumination according to the International Summit on Organic Photovoltaic Stability (ISOS) protocols [33]. While the PCE of the BAI-treated device dropped swiftly over time, the 7FBAI-treated device retained over 90% of its initial PCE after 1150 h at 25°C following the ISOS-L-1 protocol (Figure 4E). Figure 4F shows the storage stability of the devices following ISOS-D-1 protocol, where the 7FBAI-treated device can retain 85% of its initial PCE after 14,400 h storage, while the device with BAI can only be stored for approximately 6 months. The light-heat stability tests under open-circuit conditions were conducted following the ISOS-L-2 protocol under continuous 85°C heating (Figure 4G). While the BAI-based device showed a fast decay to less than 85% of its initial PCE after only 400 h, 7FBAI-based device retained over 85% of its initial PCE after about 650 h. Aging conditions of elevated temperatures of 105°C (Supporting Information S1: Figure S14) and 125°C (Supporting Information S1: Figure S15) were employed to assess the resistance of these devices to even more severe heat stimuli. While the T85 of the BAI-incorporated device is 177 h for 105°C and 61 h for 125°C accelerated aging test, the T85 for the device with 7FBAI is over 480 h for 105°C and over 200 h for 125°C (T85 means the time for a PSC to degrade to 85% of its initial PCE). Unlike the uncontrollable mixed phases caused by BAI deposition, 7FBAI-treatment contributes to a fixed surface dimensionality and thus an endurable interface that promises superior thermal stability, especially under elevated temperatures.

Conclusion

In this study, we developed a poly-fluorination strategy into traditional organic ammonium molecules as surface passivators to effectively stabilize the surface dimensionality of perovskite. The introduction of fluorine atoms allows the increased anchoring capability of the ammonium head group and introduces stronger molecular interaction with the perovskite surface framework, which effectively prevents the molecules from diffusing into the bulk. Moreover, the electron-withdrawing nature of the fluorine atoms contributes to increased steric hindrance, further fixing the surface dimensionality by inhibiting the infiltration of molecules into the perovskite lattice. The retained surface dimensionality allows an endurable interface throughout the extended operation of photovoltaic devices. With the application of 7FBAI, we observed a significant increase in the device's PCE from 24.0% to 25.2%, with a certified PCE of 24.6%, alongside remarkable thermal stability across various temperatures. Our findings highlight an effective fluorine substitution strategy to rationally regulate the surface dimensions for an endurable interface and maintain the device's performance over prolonged operational periods.

Author Contributions

Jingjing Xue, Rui Wang, Xu Zhang, and Yixin Luo conceived the idea. Xu Zhang and Yixin Luo did the device fabrication and characterization under the supervision of Jingjing Xue and Rui Wang. Yixin Luo, Xiaonan Wang, Yuan Tian, Pengju Shi, Libing Yao, Wei Fan, Jiazhe Xu, Jingyi Sun, and Qingqing Liu assisted with the device fabrication and characterizations. Yixin Luo wrote the manuscript. All the authors discussed the results and commented on the manuscript.

Acknowledgments

All the authors thank Dr. Zhong Chen and Yuan Cheng from the Instrumentation and Service Center for Molecular Sciences, Dr. Xiaohe Miao and Dr. Lin Liu from the Instrumentation and Service Center for Physical Sciences (ISCPS), and Yangyang Fan from Jiu-an Lv Group at Westlake University for the assistance in the characterizations. J. Xue and R.W. acknowledge grants (grant numbers LR24F040001, LD24E020001 and LD22E020002) from the Natural Science Foundation of Zhejiang Province of China. J. Xue acknowledges grants from the National Natural Science Foundation of China (grant number 62274146). R.W. acknowledges the support of Key R&D Program of Zhejiang (2024SSYS0061). This work was also supported by the Fundamental Research Funds for the Central Universities (226-2022-00200).

Conflicts of Interest

The authors declare no conflicts of interest.

References

National Renewable Energy Laboratory (NREL). Best Research‐Cell Efficiency Chart (NREL, 2024). Accessed October 8, 2024, https://www.nrel.gov/pv/cell-efficiency.html.

C. Wang, Y. Ding, Y. Wang, et al., “Metal Halide Perovskites for Solar‐To‐Chemical Energy Conversion in Aqueous Media,” Carbon Energy 6, no. 11 (2024): e500.

L. Zhang, Y. Wang, X. Meng, et al., “The Issues on the Commercialization of Perovskite Solar Cells,” Materials Futures 3, no. 2 (2024): 022101.

Q. Jiang, Y. Zhao, X. Zhang, et al., “Surface Passivation of Perovskite Film for Efficient Solar Cells,” Nature Photonics 13, no. 7 (2019): 460–466.

L. Zhang, H. Li, K. Zhang, et al., “Major Strategies for Improving the Performance of Perovskite Solar Cells,” iEnergy 2, no. 3 (2023): 172–199.

R. Xu, F. Pan, J. Chen, et al., “Optimizing the Buried Interface in Flexible Perovskite Solar Cells to Achieve Over 24% Efficiency and Long‐Term Stability,” Advanced Materials 36, no. 7 (2023): 2308039.

M. Li, J. Zhou, L. Tan, et al, “Brominated PEAI As Multi‐Functional Passivator for High‐Efficiency Perovskite Solar Cell,” Energy & Environmental Materials 6, no. 3 (2023): e12360.

Y. Tian, X. Zhang, K. Zhao, et al., “High‐Entropy Hybrid Perovskites With Disordered Organic Moieties for Perovskite Solar Cells,” Nature Photonics 18, no. 9 (2024): 960–966.

A. H. Proppe, A. Johnston, S. Teale, et al., “Multication Perovskite 2D/3D Interfaces Form via Progressive Dimensional Reduction,” Nature Communications 12, no. 1 (2021): 3472.

S. Teale, A. H. Proppe, E. H. Jung, et al., “Dimensional Mixing Increases the Efficiency of 2D/3D Perovskite Solar Cells,” Journal of Physical Chemistry Letters 11, no. 13 (2020): 5115–5119.

T. Zhao, C.‐C. Chueh, Q. Chen, A. Rajagopal, and A. K. Y. Jen, “Defect Passivation of Organic–Inorganic Hybrid Perovskites by Diammonium Iodide Toward High‐Performance Photovoltaic Devices,” ACS Energy Letters 1, no. 4 (2016): 757–763.

E. Ugur, E. Aydin, M. De Bastiani, et al., “Front‐Contact Passivation Through 2D/3D Perovskite Heterojunctions Enables Efficient Bifacial Perovskite/Silicon Tandem Solar Cells,” Matter 6, no. 9 (2023): 2919–2934.

G. Yan, Z. Ma, Q. Liu, et al., “Synergistic Passivation via Lewis Coordination and Electrostatic Interaction for Efficient Perovskite Solar Cells,” ACS Applied Energy Materials 6, no. 13 (2023): 7014–7024.

D. Yu, Q. Wei, H. Li, et al., “Quasi‐2D Bilayer Surface Passivation for High Efficiency Narrow Bandgap Perovskite Solar Cells,” Angewandte Chemie International Edition 61, no. 20 (2022): e202202346.

H. Chen, S. Teale, B. Chen, et al., “Quantum‐Size‐Tuned Heterostructures Enable Efficient and Stable Inverted Perovskite Solar Cells,” Nature Photonics 16, no. 5 (2022): 352–358.

W. Fu, H. Liu, X. Shi, L. Zuo, X. Li, and A. K. Y. Jen, “Tailoring the Functionality of Organic Spacer Cations for Efficient and Stable Quasi‐2D Perovskite Solar Cells,” Advanced Functional Materials 29, no. 25 (2019): 1900221.

T. Yang, L. Gao, J. Lu, et al., “One‐Stone‐For‐Two‐Birds Strategy to Attain Beyond 25% Perovskite Solar Cells,” Nature Communications 14, no. 1 (2023): 839.

Q. Wang, J. Zhu, Y. Zhao, et al., “Cross‐Layer All‐Interface Defect Passivation With Pre‐Buried Additive Toward Efficient All‐Inorganic Perovskite Solar Cells,” Carbon Energy 6, no. 9 (2024).

X. Huo, J. Lv, K. Wang, et al., “Surface Sulfidation Constructing Gradient Heterojunctions for High‐Efficiency (Approaching 18%) Htl‐Free Carbon‐Based Inorganic Perovskite Solar Cells,” Carbon Energy 6, no. 12 (2024): e586.

Y. Hao, X. Wang, M. Zhu, et al., “Sulfonyl Passivation Through Synergistic Hydrogen Bonding and Coordination Interactions for Efficient and Stable Perovskite Solar Cells,” Journal of Materials Chemistry A 10, no. 24 (2022): 13048–13054.

Z. Ma, R. Yu, Z. Xu, et al., “Crosslinkable and Chelatable Organic Ligand Enables Interfaces and Grains Collaborative Passivation for Efficient and Stable Perovskite Solar Cells,” Small 18, no. 22 (2022): e2201820.

Z. Feng, Z. Xia, Z. Wu, et al., “Efficient and Stable Perovskite Solar Cells Via Organic Surfactant Interfacial Passivation,” Solar Energy 227 (2021): 438–446.

S. Ghosh, D. Pariari, T. Behera, et al., “Buried Interface Passivation of Perovskite Solar Cells by Atomic Layer Deposition of Al2O3,” ACS Energy Letters 8, no. 4 (2023): 2058–2065.

L. N. Quan, M. Yuan, R. Comin, et al., “Ligand‐Stabilized Reduced‐Dimensionality Perovskites,” Journal of the American Chemical Society 138, no. 8 (2016): 2649–2655.

Y. Zheng, T. Niu, X. Ran, et al., “Unique Characteristics of 2D Ruddlesden–Popper (2DRP) Perovskite for Future Photovoltaic Application,” Journal of Materials Chemistry A 7, no. 23 (2019): 13860–13872.

A. Q. Alanazi, M. H. Almalki, A. Mishra, et al., “Benzylammonium‐Mediated Formamidinium Lead Iodide Perovskite Phase Stabilization for Photovoltaics,” Advanced Functional Materials 31, no. 30 (2021): 2101163.

M. Wang, Z. Shi, C. Fei, et al., “Ammonium Cations With High pKa in Perovskite Solar Cells for Improved High‐Temperature Photostability,” Nature Energy 8, no. 11 (2023): 1229–1239.

J. Hou, W. Li, H. Zhang, et al., “Synthesis of 2D Perovskite Crystals Via Progressive Transformation of Quantum Well Thickness,” Nature Synthesis 3, no. 2 (2023): 265–275.

S. M. Park, M. Wei, J. Xu, et al., “Engineering Ligand Reactivity Enables High‐Temperature Operation of Stable Perovskite Solar Cells,” Science 381, no. 6654 (2023): 209–215.

Q. Jiang, R. Tirawat, R. A. Kerner, et al., “Towards Linking Lab and Field Lifetimes of Perovskite Solar Cells,” Nature 623, no. 7986 (2023): 313–318.

C. Zhang, H. Su, and S. Zhang, “Discussions on the Arrhenius Equation,” University Chemisrty 37, no. 7 (2022): 2204035.

N. E. Courtier, “Interpreting Ideality Factors for Planar Perovskite Solar Cells: Ectypal Diode Theory for Steady‐State Operation,” Physical Review Applied 14, no. 2 (2020): 024031.

M. V. Khenkin, E. A. Katz, A. Abate, et al., “Consensus Statement for Stability Assessment and Reporting for Perovskite Photovoltaics Based on Isos Procedures,” Nature Energy 5, no. 1 (2020): 35–49.