Energy Level Alignment Research Articles

Construction of Efficient Cs2AgBiBr6 Perovskite Solar Cells by Enhancing Hole‐Selective Contact with Deep‐Level Dopant‐Free Hole Transport Material

AbstractThe mismatched energy level alignment at the hole transport interface is recognized to be a prominent limitation for the Cs2AgBiBr6‐based perovskite solar cell (PSC) to achieve high power conversion efficiency (PCE) but has not been well investigated yet. In order to solve this problem to some extent, it is proposed to balance the energy offset at the Cs2AgBiBr6 and hole transport material (HTM) interface to reduce the hole transport barriers, and a novel HTM TPTI‐TPA2F with deep level is designed to implement this strategy. The research demonstrates that, on the one hand, the planar π‐conjugation and the presence of multiple heteroatoms on TPTI‐TPA2F facilitate the formation of well‐oriented film and surface defect passivation; on the other hand, the higher film ionization potential of TPTI‐TPA2F effectively balances the energy barrier for hole transport. As a result, improved hole‐selective contact is achieved with TPTI‐TPA2F as HTM, and the interfacial energy loss is suppressed. Correspondingly, the optimized Cs2AgBiBr6 PSCs using the TPTI‐TPA2F HTM without doped feature an excellent PCE of 4.05% and a high open circuit voltage of 1.15 V, with much improved long‐term humidity and thermal stability. This work provides an attractive strategy for developing efficient Cs2AgBiBr6 PSCs.

Organic inorganic hybrid solar cell with photoactive hole transporting CuSbS2 nanoflakes

An easy-to-process, low-cost and environmentally benign organic inorganic hybrid solar cell (HSC) based on textured silicon (t-Si) is fabricated. The heterojunction solid state cell is composed of n-type t-Si having a micro-pyramidal surface with good anti-reflection properties, coated with a p-type layer of CuSbS2 nanoflakes dispersed in a polymer matrix of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The large hole density (2.7 × 1015 /cm3), high photoconductivity (5.37 mS cm−1), mono-dispersity of nanoflakes (50–80 nm), increased recombination resistance and a broad band absorption, with a band gap of ∼ 0.85 eV render CuSbS2 nanoflakes to be an ideal photo-absorber cum hole transport material for a highly scalable all solid-state HSC. Besides these attributes, the thermodynamically aligned energy levels of t-Si and CuSbS2 nanoflakes enable one-directional pathways for transfer and transport of electrons and holes to their respective contacts, yielding a high-power conversion efficiency (PCE) of 8.5 % under AM 1.5, 1 sun irradiance along with an average external quantum efficiency of 60 % superior by 39.2 % relative to its analogue devoid of CuSbS2. The effect of alkali texturization on the photovoltaic performance of the cells is also delineated by comparison with planar (pl)-Si based cells. The long-term stability of the In-Ga/t-Si/PEDOT:PSS + CuSbS2/Ag cell under intermittent illumination and storage over eight weeks confirmed from the nominal drop in PCE by ∼ 22 % demonstrates the efficacy of this affordable wet-chemistry approach for developing robust Si based HSC contrasting with the classical and expensive inorganic p-n junction crystalline Si solar cell.

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

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

Efficient Inverted Perovskite Photovoltaics Through Surface State Manipulation.

Inverted perovskite solar cells (PSCs) are considered as the most promising avenue for the commercialization of PSCs due to their potential inherent stability. However, suboptimal interface contacts between electron transport layer (ETL) (such as C60) and the perovskite absorbing layer within inverted PSCs always result in reduced efficiency and poor stability. Herein, a surface state manipulation strategy has been developed by employing a highly electronegative 4-fluorophenethylamine hydrochloride (p-F-PEACl) to effectively address the issue of poor interface contacts in the inverted PSCs. The p-F-PEACl demonstrates a robust interaction with perovskite film through bonding of amino group and Cl- with I- and Pb2+ ions in the perovskite, respectively. As such, the surface defects of perovskite film can be significantly reduced, leading to suppressed non-radiative recombination. Moreover, p-F-PEACl also plays a dual role in enhancing the surface potential and improving energy-level alignment at the interfaces between the perovskite and C60 carrier transport layer, which directly contributes to efficient charge extraction. Finally, the open-circuit voltage (Voc) of devices increases from 1.104 V to 1.157V, leading to an overall efficiency improvement from 22.34% to 24.78%. Furthermore, the p-F-PEACl-treated PSCs also display excellent stability.

Ultrafast Quasi‐2D/3D Perovskite Photodetectors Conferred Using Interfacial Engineering of Self‐Assembled Monolayers

AbstractQuasi‐2D (q‐2D) perovskites are extensively studied due to their hybrid properties of 3D and 2D phases and have proven to be applied to a wide range of optoelectronics. Multiple device engineering methods for perovskite photodetectors are developed. However, the treatment of self‐assembled monolayer (SAM) is rarely discussed. Herein, a series of silane‐coupling agents of (3‐chloropropyl)trichlorosilane (CPTS), phenyltrichlorosilane, and (3‐aminopropyl)triethoxysilane is adopted as SAM materials and elucidated their influence on q‐2D/3D CsPbBr3 films and their photodetector performance. The optical properties and morphology results reveal that perovskite film on CPTS‐modified surface can prolong excitons’ lifetime, produce a larger grain size and better size distribution, while also present better crystallinity and united orientation. As for the fabricated photodetectors, the device on a CPTS‐modified surface has the highest photocurrent of 5.46 × 10−8 A, a responsivity of 0.16 A W−1, and an 18‐times‐higher specific detectivity than the pristine counterpart, which comes from the higher surface energy and favorable energy level alignment. The photodetector on the CPTS‐modified surface also shows better stability than that on the pristine surface. This study pioneers by using SAMs on q‐2D perovskite photodetectors and provides a facile route of device fabrication for perovskite photodetectors.

Multifunctional Trifluoroborate Additive for Simultaneous Carrier Dynamics Governance and Defects Passivation to Boost Efficiency and Stability of Inverted Perovskite Solar Cells.

The main obstacles to promoting the commercialization of perovskite solar cells (PSCs) include their record power conversion efficiency (PCE), which still remains below the Shockley-Queisser limit, and poor long-term stability, attributable to crystallographic defects in perovskite films and open-circuit voltage (Voc) loss in devices. In this study, potassium (4-tert-butoxycarbonylpiperazin-1-yl) methyl trifluoroborate (PTFBK) was employed as a multifunctional additive to target and modulate bulk perovskite defects and carrier dynamics of PSCs. Apart from simultaneously passivating anionic and cationic defects, PTFBK could also optimize the energy-level alignment of devices and weaken the interaction between carriers and longitudinal optical phonons, resulting in a carrier lifetime of greater than 3 μs. Furthermore, it inhibited non-radiative recombination and improved the crystallization capacity in the target perovskite film. Hence, the target rigid and flexible p-i-n PSCs yielded champion PCEs of 24.99 % and 23.48 %, respectively. More importantly, due to hydrogen bonding between formamidinium and fluorine, the target devices exhibited remarkable thermal, humidity, and operational tracking at maximum power point stabilities. The reduced Young's modulus and residual stress in the perovskite layer also provided excellent bending stability for flexible target devices.

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

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

Unraveling Interface-Driven and Loss Mechanism-Centric Phenomena in 3D/2D Halide Perovskites: Prospects for Optoelectronic Applications.

In recent years, organic-inorganic metal halide perovskite solar cells (PSCs) have attracted considerable interest due to their remarkable and rapidly advancing efficiencies. Over the past decade, PSC efficiencies have significantly approached those of state-of-the-art silicon-based photovoltaics, making them a promising material. Currently, the scientific community widely recognizes the performance of 3D-PSCs and 2D-PSCs individually. However, when both are combined to form a heterostructure, the lattice and charge dynamics at the interface undergo a multitude of mechanisms that affect their performance. The interface between heterostructures facilitates the degradation of PSCs. The degradation pathways can be attributed to lattice distortions, inhomogeneous energy landscapes, interlayer ion migration, nonradiative recombination, and charge accumulation. This Review is dedicated to examining the phenomena that arise at the interface of 3D/2D halide perovskites and their related photophysical properties and loss mechanism processes. We mainly focus on the impact of lattice mismatch, energy level alignment, anomalous carrier dynamics, and loss mechanisms. We propose a "cause-impact-identify-rectify" approach to gain a comprehensive understanding of the ultrafast processes occurring within the material. Finally, we highlight the importance of advanced spectroscopic and imaging techniques in unraveling these intricate mechanisms. This discussion delves into the future possibilities of fabricating 3D/2D heterostructure-based optoelectronic devices, pushing the boundaries of performance across diverse fields. It envisions the creation of devices with unparalleled capabilities, exceeding the limitations of current technologies.

Anomalously bright single-molecule upconversion electroluminescence

Efficient upconversion electroluminescence is highly desirable for a broad range of optoelectronic applications, yet to date, it has been reported only for ensemble systems, while the upconversion electroluminescence efficiency remains very low for single-molecule emitters. Here we report on the observation of anomalously bright single-molecule upconversion electroluminescence, with emission efficiencies improved by more than one order of magnitude over previous studies, and even stronger than normal-bias electroluminescence. Intuitively, the improvement is achieved via engineering the energy-level alignments at the molecule−substrate interface so as to activate an efficient spin-triplet mediated upconversion electroluminescence mechanism that only involves pure carrier injection steps. We further validate the intuitive picture with the construction of delicate electroluminescence diagrams for the excitation of single-molecule electroluminescence, allowing to readily identify the prerequisite conditions for producing efficient upconversion electroluminescence. These findings provide deep insights into the microscopic mechanism of single-molecule upconversion electroluminescence and organic electroluminescence in general.

A Hole-Selective Self-Assembled Monolayer for Both Efficient Perovskite and Organic Solar Cells.

Self-assembled monolayers (SAMs) emerging as promising hole-selective layers (HSLs) are advantageous for facile processability, low cost, and minimal material consumption in the fabrication of both perovskite solar cells (PSCs) and organic solar cells (OSCs). However, owing to the different nature between perovskites and organic semiconductors, few SAMs were reported to effectively accommodate both PSCs and OSCs at the same time. In this regard, a universally applicable SAM that can accommodate both perovskites and organic semiconductors could be desirable for simplifying cell manufacturing, especially from an industrial perspective. In this work, we designed a SAM, TDPA-Cl by introducing chlorinated phenothiazine as the headgroup and linking with anchor phosphonic acid through a butyl chain. The resulting dense SAM was carefully characterized in terms of molecular bonding, surface morphology, and packing density, and its functions in OSCs and PSCs were discussed from the aspects of interactions with the absorber layer, energy level alignment, and charge-selective dipoles. The PM6:Y6-based OSCs with TDPA-Cl SAM as the HSL showed a superior performance to those with PEDOT:PSS. Furthermore, the universality was proved with an efficiency of 17.4% in the D18:Y6 system. In PSCs, the TDPA-Cl-based devices delivered a better performance of 22.4% than the PTAA-based devices (20.8%) with improved processability and reproducibility. This work represents a SAM with reasonably good compromise between the differing requirements of OSCs and PSCs.

Utilizing rubidium chloride as an effective andstable interface modification layer forhigh-efficiency solar cells.

The presence of interface defects between the perovskite layer and the underlying substrate has a significant impact on the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). S n O 2 thin films are employed in PSCs as electron transport layers to achieve high PCE. However, the significant lattice mismatch between S n O 2 and the perovskite material leads to a large number of uncoordinated defects at the interface between perovskite and substrate, resulting in recombination losses at the interface. In this study, rubidium chloride (RbCl) was introduced as the interface modification layer between the perovskite layer and the S n O 2 electron transport layer to enhance the PCE of PSCs. The research showed that the RbCl interface modification layer effectively passivated the under-coordinated defects of Sn ions and optimized the energy level alignment between the perovskite layer and the S n O 2 film. Moreover, the fabricated PSCs exhibited an open-circuit voltage of 1.11V and a power conversion efficiency of 21.64%. Furthermore, the device maintained 80% of initial efficiency after storage for 30days in an inert gas environment and 60% of the value after storage for 30days in ambient air.

Bi/Bi2O3/TiO2 heterojunction photocathode for high-efficiency visible-light-driven lithium-sulfur batteries: Advancing light harvesting and polysulfide conversion

Integrating solar-electrical energy conversion and electrical-chemical energy storage functions within a single device offers a promising strategy for efficient light harvesting, conversion, and storage of renewable solar energy. Herein, we develop visible-light-driven photoelectrochemical Li2S6-based lithium-sulfur batteries (VPLSBs) for simultaneous energy conversion and storage, employing a versatile Bi/Bi2O3/TiO2 photocathode as both a light harvester and redox catalyst. The narrowed band gap of photocathode minimizes photoelectron-hole recombination, enabling efficient light-to-electrical energy conversion. Its energy level alignment with Li-S electrochemical potentials facilitates the photocarriers’ participation in polysulfide conversions, supporting electrical-to-chemical energy storage. Under visible light, the Bi/Bi2O3/TiO2 photocathode exhibits a photoelectrocatalysis effect, enhancing interfacial charge transfer, reducing Li2S deposition resistance, and ensuring stable Li2S plating/stripping. Additionally, the bare photo-charging process achieves an overall energy conversion-storage efficiency of 2.58 %. The VPLSB demonstrates an exceptional specific capacity of 1484 mA h g−1 over 900 cycles, maintaining an apparent energy efficiency of 100.2 % at 0.2 mA cm−2.

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.

Boosting the efficiency of organic solar cells based on a highly planar π-conjugated solid additive working as the sensitizer

Solid additives have been demonstrated as a simple and effective approach to improve the performance of organic solar cells (OSCs). The exploitation of excellent solid additive is an important aspect to obtain efficient OSC. This research designs and synthesizes a novel solid additive IDT(BDT-IC)2 as the sensitizer for OSCs. The IDT(BDT-IC)2 is an A-π-d-π-A type molecule, which possesses a highly planar π-conjugated structure. This molecule exhibits a complementary light absorption with suitable energy levels, which meets the requirement of a qualified sensitizer. It helps to enhance the external quantum efficiency spectrum of the device. Thus, an increased photocurrent is achieved. The addition of IDT(BDT-IC)2 promotes the formation of a cascade energy level alignment and tunes the miscibility of the active layer. Both the exciton dissociation and electron transportation are improved, which enhances the fill factor. As a result, the average power conversion efficiency (PCE) of the PM6:Y6 OSC is increased from 15.75 % of the control device to 16.34 % by incorporating merely 0.25 wt% of IDT(BDT-IC)2. And the highest PCE with a value of 16.70 % is obtained. This research offers a facile and effective strategy for highly efficient OSCs by applying solid additive as the sensitizer.

Quantifying Non‐Radiative Recombination in Passivated Wide‐Bandgap Metal Halide Perovskites Using Absolute Photoluminescence Spectroscopy

AbstractWide‐bandgap (>1.6 eV) mixed‐halide perovskites tend to experience notable open‐circuit voltage losses in solar cells due to non‐radiative recombination. Here, the effects of defects and their passivation on the non‐radiative recombination of charge carriers in mixed‐halide perovskite solar cells are studied. By determining the quasi‐Fermi level splitting via absolute photoluminescence measurements of perovskite layers with and without charge transport layers, bulk and interface contributions are disentangled and compared to the radiative open‐circuit voltage. For wide‐bandgap perovskites, non‐radiative recombination present in the pristine perovskite layers increases with increasing bandgap. The most prominent loss, located at the perovskite – electron transport layer interface (ETL), can be reduced by interface passivation for the different bandgaps studied (1.58 to 1.82 eV) to a level close to that of the intrinsic losses. By combining light‐intensity‐dependent absolute photoluminescence spectroscopy with sensitive spectral photocurrent measurements it is found that different passivation agents result in a similar decrease of the non‐radiative recombination for different bandgaps. This suggests that the gained open‐circuit voltage is not due to an improved energy level alignment at the perovskite – ETL interface. Instead, passivation involves eliminating the direct contact between the perovskite semiconductor and the ETL.

CP-AFM Molecular Tunnel Junctions with Alkyl Backbones Anchored Using Alkynyl and Thiol Groups: Microscopically Different Despite Phenomenological Similarity.

In this paper, we report results on the electronic structure and transport properties of molecular junctions fabricated via conducting probe atomic force microscopy (CP-AFM) using self-assembled monolayers (SAMs) of n-alkyl chains anchored with acetylene groups (CnA; n = 8, 9, 10, and 12) on Ag, Au, and Pt electrodes. We found that the current-voltage (I-V) characteristics of CnA CP-AFM junctions can be very accurately reproduced by the same off-resonant single-level model (orSLM) successfully utilized previously for many other junctions. We demonstrate that important insight into the energy-level alignment can be gained from experimental data of transport (processed via the orSLM) and ultraviolet photoelectron spectroscopy combined with ab initio quantum chemical information based on the many-body outer valence Green's function method. Measured conductance GAg < GAu < GPt is found to follow the same ordering as the metal work function ΦAu < ΦAu < ΦPt, a fact that points toward a transport mediated by an occupied molecular orbital (MO). Still, careful data analysis surprisingly revealed that transport is not dominated by the ubiquitous HOMO but rather by the HOMO-1. This is an important difference from other molecular tunnel junctions with p-type HOMO-mediated conduction investigated in the past, including the alkyl thiols (CnT) to which we refer in view of some similarities. Furthermore, unlike in CnT and other junctions anchored with thiol groups investigated in the past, the AFM tip causes in CnA an additional MO shift, whose independence of size (n) rules out significant image charge effects. Along with the prevalence of the HOMO-1 over the HOMO, the impact of the "second" (tip) electrode on the energy level alignment is another important finding that makes the CnA and CnT junctions different. What ultimately makes CnA unique at the microscopic level is a salient difference never reported previously, namely, that CnA's alkyne functional group gives rise to two energetically close (HOMO and HOMO-1) orbitals. This distinguishes the present CnA from the CnT, whose HOMO stemming from its thiol group is well separated energetically from the other MOs.

Superior Intermolecular Noncovalent Interactions Empowered Dopant‐Free Hole Transport Materials for Efficient and Stable Sb2(S,Se)3 Solar Cells

AbstractAntimony selenosulfide (Sb2(S,Se)3) solar cells are critically restrained by the Sb2(S,Se)3/charge transport layer interface with scarce carriers transfer ability and high density of deep‐level defect‐induced traps, which are prone to spark the nonradiative recombination and capture the benign photogenerated carriers. Herein, utilizing the intermolecular noncovalent interactions strategy in molecular stereoscopic structural engineering, two dopant‐free hole transport materials (HTMs) are constructed, coded as T‐BDT and F‐BDT, with synergistic hole selectivity and interfacial healing ability. The theoretical simulation and experimental results decipher that the F‐BDT possesses the more favorable planarized conformation, charge delocalization/coupling and molecular stacking pattern, which endow it with the salient hole selection, robust interface passivation and appropriate energy level alignment. Consequently, the Sb2(S,Se)3 solar cell with F‐BDT as dopant‐free HTM realize an outstanding power conversion efficiency of 9.13%, hitting the record high for Sb2(S,Se)3 devices under dopant‐free conditions.

Buried Interface‐The Key Issues for High Performance Inverted Perovskite Solar Cells

AbstractInterface engineering is known for effectively improving interfacial contact and passivating defects to enhance device performance of inverted perovskite solar cells (PSCs). Currently, most of works focus on surface passivation, while the buried interface is equally important. The film quality of perovskite layer greatly relies on the buried interface, leaving a pronounced impact on overall device performance. In addition, resolving defects and energy level mismatch at buried interface remains challenging. Optimizing the buried interface becomes a promising approach for high‐efficiency inverted PSCs. This review summarizes recent advances in buried interface engineering and emphasize the importance of corresponding characterization techniques. The various functions of buried interface engineering are carefully discussed, including crystallization modulation, defect passivation, energy level alignment, chemical reaction inhibition, chemical bridge, dipole cancellation and novel buried interfacial techniques. Finally, current challenges and prospects are put forward that should be addressed to further improve device performance of inverted PSCs.

Wide‐Bandgap Polymers with a C(sp3)─F Polyfluoride Backbone Enable High‐Efficient Ternary Organic Solar Cells

AbstractFluorination strategy is demonstrated to be a successful approach for optimizing the electron distribution and morphology of organic photovoltaic materials. The previous works focus on introducing only a few C(sp2)─F bonds into conjugated backbone or C(sp3)─F bonds into sidechains. Herein, a new strategy by introducing C(sp3)─F polyfluoride unit into the backbone is proposed, wherein the fluorine atoms are not involved into the conjugation but can promote the intermolecular interaction between backbones. Two wide‐bandgap fluoropolymers are prepared and employed as the third component for ternary organic solar cells. As expected, even if there are six fluorine atoms in a single repeat unit, the relevant fluoropolymers possess complementary absorption and aligned energy levels. More importantly, the polyfluoride backbone affords adequate non‐covalent interactions, consequently enhancing the polymer aggregation and packing order, which is verified by a fibril‐like morphology in the blend film with the host polymer PM6 and only 10 wt.% fluoropolymer. In addition, the decreased surface energy caused by polyfluoride unit is beneficial for the improvement of domain purity and the formation of nanoscale phase separation between donor and acceptor materials. As a result, the fluoropolymer‐assisted ternary device displays a higher efficiency of 18.74% compared with the binary device (17.39%).

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.