Perovskite Interface Research Articles

Homogeneous crystallization and buried interface passivation for perovskite tandem solar modules.

Scalable fabrication of all-perovskite tandem solar cells is challenging because the narrow-bandgap subcells made of mixed lead-tin (Pb-Sn) perovskite films suffer from nonuniform crystallization and inferior buried perovskite interfaces. We used a dopant from Good's list of biochemical buffers, aminoacetamide hydrochloride, to homogenize perovskite crystallization and used it to extend the processing window for blade-coating Pb-Sn perovskite films and to selectively passivate defects at the buried perovskite interface. The resulting all-perovskite tandem solar module exhibited a certified power conversion efficiency of 24.5% with an aperture area of 20.25 square centimeters.

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.

Optimizing SnO2 Quantum Dot Precursor Solutions for Perovskite Solar Cells with Reduced Hysteresis

In recent years, SnO2 quantum dots (QDs) have been widely used for preparing the electron‐transport layer within perovskite solar cells (PSCs). However, the fabricated devices exhibit an evident hysteresis unless interlayer materials are introduced to passivate or prevent the formation of trap states at the SnO2–perovskite interface. Herein, the use of the zwitterion 3‐(1‐pyridinio)‐1‐propanesulfonate (PPS) as additive inside the SnO2 QDs solution is proposed. The results highlight that the PPS plays a multifunctional role by accelerating the synthesis of the QDs, enhancing the electron transfer and passivating defects at the SnO2–perovskite interface. The resulting PSCs with SnO2 QDs incorporating PPS exhibit a remarkable reduction in hysteresis index (HI) compared to those prepared with thiourea or without any additives. This reduction in HI suggests that PPS serves as a cost‐effective alternative additive for SnO2 QDs preparation, eliminating the need for additional interlayers or expensive additives.

Ionic Bonding Without Directionality Facilitates Efficient Interfacial Bridging for Perovskite Solar Cells.

Interface passivation through Lewis acid-base coordinate chemistry in perovskite solar cells (PSCs) is a universal strategy to reduce interface defects and hinder ion migration. However, the formation of coordinate covalent bonding demands strict directional alignment of coordinating atoms. Undoubtedly, this limits the selected range of the interface passivation molecules, because a successful molecular bridge between charge transport layer and perovskite bottom interface needs a well-placed molecular orientation. In this study, it is discovered that potassium ions can migrate to the hollow sites of multiple iodine ions from perovskite to form K-Ix ionic bonding, and the ionic bonds without directionality can support molecular backbone rotation to facilitate polar sites (carboxyl groups) chelating Pb at the bottom perovskite interface, finally forming a closed-loop bonding structure. The synergy of coordinate and ionic bonding significantly reduces interface defects, changes electric field distribution, and immobilizes iodine at the perovskite bottom interface, resulting in eliminating the hysteresis effect and enhancing the performance of PSCs. As a result, the corresponding devices achieve a high efficiency exceeding 24.5% (0.09 cm2), and a mini-module with 21% efficiency (12.4 cm2). These findings provide guidelines for designing molecular bridging strategies at the buried interface of PSCs.

Surface repair of wide-bandgap perovskites for high-performance all-perovskite tandem solar cells

Wide-bandgap (WBG) perovskite solar cells (PSCs) play a fundamental role in perovskite-based tandem solar cells. However, the efficiency of WBG PSCs is limited by significant open-circuit voltage losses, which are primarily caused by surface defects. In this study, we present a novel method for modifying surfaces using the multifunctional S-ethylisothiourea hydrobromide (SEBr), which can passivate both Pb-I and FA-I terminated surfaces. Moreover, the SEBr upshifted the Fermi level at the perovskite interface, thereby promoting carrier collection. This proposed method was effective for both 1.67 and 1.77 eV WBG PSCs, achieving power conversion efficiencies (PCEs) of 22.47% and 19.90%, respectively, with VOC values of 1.28 and 1.33 V, along with improved film and device stability. With this advancement, we were able to fabricate monolithic all-perovskite tandem solar cells with a champion PCE of 27.10%. This research offers valuable insights for passivating the surface trap states of WBG perovskite through rational multifunctional molecular engineering.

SnO2-Perovskite Interface Engineering Based on Bifacial Passivation via Multifunctional N-(2-Acetamido)-2-aminoethanesulfonic Acid toward Efficient and Stable Solar Cells.

Bifacial passivation on both electron transport materials and perovskite light-absorbing layers as a straightforward technique is used for gaining efficient and stable perovskite solar cells (PSCs). To develop this strategy, organic molecules containing multiple functional groups can maximize the effect of defect suppression. Based on this, we introduce N-(2-acetamido)-2-aminoethanesulfonic acid (ACES) at the interface between tin oxide (SnO2) and perovskite. The synergistic effect of multiple functional groups in ACES, including amino, carbonyl (C═O), and sulfonic acid (S═O) groups, promotes charge extraction of SnO2 and provides an improved energy level alignment for charge transfer. Furthermore, S═O in ACES effectively passivates the defects of uncoordinated Pb2+ in perovskite films, resulting in enhanced crystallinity and decreased nonradiative recombination at the buried interface. The power conversion efficiency (PCE) of related PSCs increases from 20.21% to 22.65% with reduced J-V hysteresis after interface modification with ACES. Notably, upon being stored at a low relative humidity of 40 ± 5% over 2000 h and high relative humidity of 80 ± 5% over 1000 h, the unencapsulated ACES-modified device retains up to 90% and 80% of their initial PCE, respectively. This study deepens defect passivation engineering on the buried interface of perovskites for realizing efficient and stable solar cells.

Surface Reconstruction via Molten Chloride Salt for Efficient and Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs) have attracted significant attention due to their high efficiencies that are closely associated with the optimized interface of perovskite (PVK) films. However, during film deposition, tremendous interfacial defects are generated in PVK films, which suppress device performance. Herein, we employ an organic molten chloride salt of 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) on the PVK surface to regulate the interface properties through surface reconstruction by heating to 110 °C, during which DMTMM undergoes an obvious phase transition from a solid to liquid molten salt. The mobile phase coordinates with unsaturated Pb2+ and halide vacancies to heal the structural defects. After the mixture cools to room temperature, a compact DMTMM interlayer is formed to protect PVKs from degradation in the air. Consequently, the DMTMM-treated MAPbI3-based PSCs yield a champion PCE approaching 20% with optimized stability. This molten-salt-assisted surface reconstruction strategy provides a new approach to establish highly stable hybrid perovskite films for high-performance PSCs.

All‐Inorganic Perovskite Solar Cells: Modification Strategies and Challenges

Cesium‐based all‐inorganic wide‐bandgap perovskite solar cells (AIWPSCs) have been demonstrated with exceptional optoelectronic properties such as intrinsic optical wide‐bandgap and high thermal stability, which make them suitable candidates for the front sub‐cells of tandem solar cells (TSCs). Passivation of perovskite surface and interface is a matter of common interest in this community since all‐inorganic perovskites always suffer from non‐ideal crystallization such as phase impurity, high defect density, and non‐uniform morphology. Despite these shortcomings, numerous efforts have been devoted in recent years to pursuing high‐performance AIWPSCs, which exhibit an abruptly increased power conversion efficiency (PCE) from 2.9% to over 21.0%. In view of not having a thorough summary about the advancements on AIWPSCs, herein, a comprehensive review is given to highlight the recent device performance progress of AIWPSC, particularly focusing on the strategies to passivate the defects of all‐inorganic perovskite, namely, additive engineering, solvent engineering, interface modification, and the exploration of new charge transport materials (CTMs) for improving the phase stability and PCE of AIWPSCs. Finally, a conclusive outlook on AIWPSCs will be given to provide our perspectives aiming to inspire the further development of AIWPSCs.

Investigation of the Role of K2SO4 Electrolyte in Hole Transport Layer for Efficient Quasi-2D Perovskite Light-Emitting Diodes.

Quasi-two-dimensional (2D) perovskite light-emitting diodes are promising light sources for color display and lighting. However, poor carrier injection and transport between the bottom hole transport layer (HTL) and perovskite limit the device performance. Here we demonstrate a simple and effective way to modify the HTL for enhancing the performance of perovskite light-emitting diodes (PeLEDs). An electrolyte K2SO4 is used to mix with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as the hole transport layer. The K+ doping helped the quasi-2D perovskite phases grow vertically along the interface of the PEDOT:PSS, fine-modulate the phase distribution, and simultaneously reduce the defect density of quasi-2D perovskites. It also significantly reduced the exciton quenching and injection barrier at PEDOT:PSS and quasi-2D perovskite interface. The optimized green PeLEDs with the K2SO4 doped PEDOT:PSS HTL showed a maximum luminance of 17185 cd/m2 which is almost 4.7 times brighter than the control one, with a maximum external quantum efficiency of 18.64%.

Understanding the Anomalous J–V Curves in Carbon‐Based Perovskite Solar Cells as a Structural Transition Induced by Ion Diffusion

The investigation of hole transport layer‐free mesoporous carbon perovskite solar cells by analyzing current–voltage (J–V) curves under different scan rates, light intensities, and temperatures is presented. A distinctive bump in the curves is identified, previously reported in the literature. The voltage at the inflection point of this transition shows a linear correlation with the scan rate, directly yielding a characteristic relaxation time. Increasing temperature demonstrates a reduction in the magnitude and characteristic time of the bump. It also indicates an activation energy of 0.8 eV, suggesting a diffusion mechanism. Importantly, the intensity of the illumination has no influence on the overall behavior, indicating that the phenomenon is not a photovoltaic processes. It is proposed that the bump originates from transition between a metastable state at high scan rates and a stable one reached after relaxation. To accurately replicate the measured J–V curves, a novel lumped circuit model is introduced and validated. A schematic microstructural model depicts the reversible reduction in photocurrent as a decline in charge transfer capacity caused by the diffusion of large ions at the mesoporous titanuim dioxyde interface. Ultimately, this study also suggests a plausible reason for the well‐known hysteresis commonly observed with perovskite solar cells.

Simultaneous Passivation of Perovskite Interfaces at Multiple Active Sites Improves Device Performance: Combining Theory and Experiment.

A multisite interface passivation material named 2-mercapto-4-methyl-5-thiazoleacetic acid (MMTA) is used to optimize the perovskite film top interface. DFT calculations and experiments show that MMTA can effectively passivate interface defects. Finally, the champion device's photoelectric conversion efficiency reached 23.44%, which possessed long-term stability.

Ambipolar Charge Carrier Transport Properties at the S-Benzyl-l-cysteine-Induced 2D/3D Halide Perovskite Interface

Ambipolar Charge Carrier Transport Properties at the S-Benzyl-<scp>l</scp>-cysteine-Induced 2D/3D Halide Perovskite Interface

Post‐Synthetic Interstitial Metal Doping for Efficient and Stable 3D/2D Heterostructured Perovskite Solar Cells

AbstractPerovskite solar cells (PSCs) have experienced exceptional development in recent years, due to their outstanding photoelectronic properties and low‐cost solution processing. Many state‐of‐the‐art PSC designs have been effectively demonstrated using a stacked 3D perovskite/2D perovskite heterostructure, yet limitations arise due to the low conductivity of the 2D perovskite, the hidden buried interface of 3D perovskite, and halide ion migration within 3D/2D PSC device under operational bias. Here, these limitations are overcome by developing a novel and universal post‐synthetic metal (Zn2+) doping strategy and realizing 3D/2D PSCs with superior efficiency and stability. Informed by ab initio calculations and synchrotron fine structure experiments, it is revealed that the introduced zinc ions are energetically favored at interstitial crystal sites, subsequently hindering the migration of halide ions and producing a beneficial shift toward a more n‐type character in the buried 3D perovskite interface. Combined with extensive photophysical characterization, the Zn2+‐modified 3D/2D perovskite thin film is shown to strongly recover its photo‐carrier conductivity compared with the 3D/2D perovskite film, boosting the efficiency (22.90%) of PSCs while exhibiting improved humidity and operational stability.

Suppressing Redox Reactions at the Perovskite-Nickel Oxide Interface with Zinc Nitride to Improve the Performance of Perovskite Solar Cells.

For p-i-nperovskite solar cells (PSCs), nickel oxide (NiOx) hole transport layers (HTLs) are the preferred interfacial layerdue to their low cost, high mobility, high transmittance, and stability. However, the redox reaction between the Ni≥3+ and hydroxyl groups in the NiOx and perovskite layer leads to oxidized CH3NH3 + and reacts with PbI in the perovskite, resulting in a large number of non-radiative recombination sites. Among various transition metals, an ultra-thin zinc nitride (Zn3N2) layer on the NiOx surface is chosen to prevent these redox reactions and interfacial issues using a simple solution process at low temperatures. The redox reaction and non-radiative recombination at the interface of the perovskite and NiOx reduce chemically by using interface modifier Zn3N2 to reduce hydroxyl group and defects on the surface of NiOx. A thin layer of Zn3N2 at the NiOx/perovskite interface results in a high Ni3+/Ni2+ ratio and a significant work function (WF), which inhibits the redox reaction and provides a highly aligned energy level with perovskite crystal and rigorous trap-passivation ability. Consequently, Zn3N2-modified NiOx-based PSCs achieve a champion PCE of 21.61%, over the NiOx-based PSCs. After Zn3N2 modification, the PSC can improve stability under several conditions.

Charge Carrier Dynamics at Carbon/Perovskite Interface: Implications on Carbon‐Based HTM‐Free Solar Cell Stability

Carbon‐based hole transport material (HTM)‐free perovskite solar cells (CPSCs) are an innovative device architecture that mitigates inherent challenges associated with record‐breaking perovskite solar cells (PSCs), which rely on metal/HTMs, including instability, manufacturing intricacy, and elevated costs. The photovoltaic efficiency and stability of CPSCs are profoundly influenced by the charge carrier dynamics at the interfaces. Herein, the charge carrier dynamics at the carbon(C)–perovskite interface in CPSCs and its implications on photovoltaic performances and stability, an aspect that has received limited exploration thus far are probed, are investigated using transient surface photovoltage (Tr‐SPV) and transient photoluminescence measurements. The study reveals that the C‐electrode effectively acts as a selective barrier, impeding electrons while facilitating the extraction of holes at the C–perovskite interface. This selective blocking mechanism holds significant implications for improving the performance and stability of CPSCs over HTM‐free PSCs with gold(Au) electrodes. The stability of CPSCs is evaluated by measuring shelf life, maximum power point tracking, Tr‐SPV, and X‐Ray diffraction measurements. By delving into these pivotal aspects, this work aims to contribute to the advancement and understanding of CPSCs for sustainable and efficient energy conversion.

Critical role of dopant in NiOx hole transport layer for mitigating redox reactivity at NiOx/absorber interface in mixed cation perovskite solar cells.

Redox chemistry transpiring at the interface of NiOx hole transport layer (HTL) and perovskite absorber is a critical phenomenon leading to relatively low values of open circuit voltage (VOC) and fill factor (FF), in turn hampering the overall device performance and stability. In this work, for the first time, the hard acid electronic nature of vanadium (V) dopant in nickel oxide HTL is opportunely exploited to mitigate the undesirable Lewis acid-base reactions occurring at the HTL/mixed-cation perovskite interface. The findings of the study show that vanadium doping results in improved interfacial energetics along with decreased VOC loss, confirming that despite the increase in Ni3+/Ni2+ ratio with the vanadium dopant, the redox reaction catalyzed by Ni3+ ions is kept under check. Vanadium doping also aided in the realization of superior perovskite films with lower Urbach energy, which translated into one order increase in maximum photoinduced carrier generation rate per unit volume. Carrier dynamics investigations show fewer defect states (lower VTFL) and trap-assisted recombination (lower diode ideality factor), which optimize the devices' photovoltaic performance. These benefits collectively contribute to low-loss charge transfer across the NiOx/mixed-cation perovskite interface, which increases the relative efficiency by ∼30% for 5 wt% V-doped NiOx devices compared to pristine NiOx devices, augmented by an increase in device J-V parameters like open circuit voltage (VOC), short circuit current density (JSC), and fill factor (FF).

NiOx/PANI nanocomposite doped carbon paste as electrode for long-term stable and highly efficient perovskite solar cells.

Carbon-based perovskite solar cells (PSCs) have emerged as a hopeful alternative in the realm of photovoltaics. They are considered promising due to their affordability, remarkable durability in humid environments, and impressive electrical conductivity. One approach to address the cost issue is to use affordable counter electrodes in PSCs that do not require organic hole transport materials (HTMs). This study utilized an innovative and economical method to create NiOx/PANI nanocomposites. Later, these nanoparticles were integrated into a carbon paste to act as an HTM. This incorporation is intended to optimize charge extraction, improve interfacial contact, align energy levels, reduce energy loss, minimize charge recombination, and protect the perovskite (FAPbI3) surface from degradation. The optoelectronic properties of these devices were investigated, and all cells showed improved efficiency compared to control cells. The NiOx/PANI doped carbon (NiOx/PANI+CE) exhibited excellent performance due to strong hole conductivity, well-aligned energy levels, and the formation of stepwise band alignment at the perovskite interface.

Translucent solar power for potential future implementations

This review focuses on recent advancements in semitransparent perovskite solar cells, including perovskite compositions, interface engineering and cutting-edge transparent electrodes.

Fluorene- and fluorenone-based molecules as electron-transporting SAMs for photovoltaic devices.

New semiconductors containing fluorene or fluorenone central fragments along with phosphonic acid anchoring groups were synthesized and investigated as electron transporting materials for possible application in photovoltaic devices. These derivatives demonstrate good thermal stability and suitable electrochemical properties for effective electron transport from perovskite, Sb2S3 and Sb2Se3 absorber layers. Self-assembled fluorene and fluorenone electron-transporting materials have shown improved substrate wettability, indicating bond formation between monolayer-forming compounds and the ITO, TiO2, Sb2S3, or Sb2Se3 surface. Additionally, investigated materials have compatible energetic band alignment and can passivate perovskite interface defects, which makes them interesting candidates for application in the n-i-p structure perovskite solar cell.

Amino acid salt induced PbI2 crystal orientation optimization for high-efficiency perovskite solar cells with long-term stability

By introducing potassium l-glutamate, residual PbI2 at the buried perovskite interface is eliminated, leading to enhanced photoelectric performance in perovskite solar cells.