Effective Defect Passivation Research Articles

Unlocking Near 100% PLQY: The Impact of Post‐Treatment on Emission Efficiency of Mn2+: CsPbCl3 Nanocrystals

AbstractMn2+ doped CsPbCl3 nanocrystals (Mn2+:CsPbCl3 NCs) show immense promise in lighting and display technologies owing to their outstanding optical characteristics. Nonetheless, high defect density, inefficient Mn2+ doping, and poor structural robustness pose considerable challenges in the synthesis of Mn2+:CsPbCl3 NCs with high photoluminescence quantum yield (PLQY) and long‐term stability. This study introduces an eco‐friendly room‐temperature post‐treatment method utilizing MgCl2/oleylamine solution, boosting the total PLQY of the NCs from 65% to 98%, including a 30% increase for Mn2+ emission. Additionally, the post‐treatment significantly improves the NCs’ resilience against UV light, retaining 80% of their initial PL intensity after 120 hours of UV exposure. Comprehensive analyses including density functional theory simulation and temperature‐dependent PL spectra suggested that the PLQY enhancement is due to the improved Mn2+ doping efficiency and the effective passivation of native vacancy defects. The stability of the NCs is enhanced by replacing Pb2+ with Mg2+ and Mn2+, mitigating lattice distortions within the [PbCl6]4− octahedral framework. The color rendering index of white light‐emitting diodes fabricated with the post‐treated Mn2+:CsPbCl3 NCs achieves an exceptional value of 98. This work offers novel insights into the fabrication of high‐PLQY Mn2+:CsPbCl3 NCs, advancing the practical deployment of perovskite nanomaterials in various industries.

Enhancing the performance and stability of organometal halide perovskite by using a feasible and economical interface material

AbstractOrganometal halide perovskites (OHPs) are one of the viable options for solar absorber materials because their power conversion efficiencies are getting better and better over time. In the conventional n-i-p-based configuration, TiO2 has been widely used as an electron transport layer (ETL). However, a number of constraints, such as low electron mobility and a mismatched band alignment with perovskite, restrict future advances in solar performance and device environmental stability. As a result, SnO2 has garnered a lot of interest as a potential replacement due to the comparatively low manufacturing temperature, better electron mobility and appropriate energy alignment w.r.t perovskite. In this experimental work, the primary emphasis was placed on enhancing the efficiency as well as the stability of OHPs by performing interface engineering at the ETL (SnO2)/perovskite interface. We improved the surface quality of the SnO2 ETL layer by using a material called 8-Hydroxyquinoline, which was quite inexpensive, and we prepared a favourable plane for the deposition of perovskite. Remarkably, the proposed surface modification material made the SnO2 layer easier to wet and impacted the growth of perovskite grains. This made the perovskite layer more compact and smooth. Our experimental findings imply that the OHPs’ enhanced charge recombination resistance and decreased charge transfer resistance are caused by effective defect passivation at the junction of the SnO2 and perovskite films, as well as a decrease in recombination due to unwanted trap states. The fabricated cell produced a power conversion efficiency (PCE) of 20.42%, higher than a PCE of 17.9% obtained for a device without surface modification. The proposed material for changing the surface also made OHPs more stable by reducing the surface paths for the reaction with humidity and reducing the amount of extra PbI2 in the perovskite layer. Various research groups have investigated the modification of SnO2 ETL using interfacial engineering methods and have contributed to enhancing OHPs’ solar performance and device stability.

An Orientation-Enhanced Interlayer Enables Efficient Sn-Pb Binary Perovskite Solar Cells and All-Perovskite Tandem Solar Cells with High Fill Factors.

The performance of narrow-bandgap (NBG) perovskite solar cells (PSCs) is limited by the severe nonradiative recombination and carrier transport barrier at the electron selective interface. Here, we reveal the importance of the molecular orientation for effective defect passivation and protection for Sn2+ at the perovskite/C60 interface. We constructed an internally self-anchored dual-passivation (ISADP) layer, where the orientation of PCBM can be significantly enhanced by the interaction between ammonium and carbonyl groups. It can facilitate the contact with C60 and minimize the nonradiative energy loss at the electron transport interface. This strategy remarkably enhances the FF of NBG PSCs, from 77.45% to 82.88%, and the power conversion efficiency (PCE) from 20.67% to 24.02%. Moreover, monolithic all-perovskite TSCs exhibit a high certified PCE (under reverse scan) of 28.12% and a record FF of 84.25%. This work opens up a new pathway for enhancing the performance of monolithic all-perovskite TSCs.

Dual-interface passivation to improve the efficiency and stability of inverted flexible perovskite solar cells by in-situ constructing 2D/3D/2D perovskite double heterojunctions

Perovskite solar cells (PSCs) have demonstrated considerable potential as a promising photovoltaic technology. Nevertheless, the continued advancement is impeded by the presence of interfacial defects, which give rise to nonradiative recombination and ion migration. In this work, we demonstrate a simple and effective method to in-situ construct 2D/3D/2D perovskite double heterojunctions for effective passivation of defects and mitigation of ion migration in 3D perovskites. As a result, the inverted double-heterojunction PSCs exhibited a high power conversion efficiency (PCE) of 24.08 % with a low VOC loss of 0.37 V due to the minimal nonradiative recombination by dual-interface passivation. The stability of double-heterojunction devices has been significantly improved, maintaining 92 % of the initial value after 3000 h of storage under indoor light in a N2 atmosphere. Especially, the 2D/3D/2D perovskite double heterojunctions are applicable to flexible PSCs (FPSCs) to enhance both PCE and mechanical stability by effective residual stress release. Consequently, the FPSCs demonstrated a PCE of 21.58 % while retaining 86 % of the initial PCE even after undergoing a multi-cycle bending test for 10,000 cycles.

Synergetic Dual‐Additive Strategy for Regulating Crystallization and Defect Passivation of Perovskite Nanograin Toward Efficient Light‐Emitting Diodes

AbstractPerovskite nanograins with a dimension larger than the Bohr exciton diameter have significant advantages in achieving high‐performance light‐emitting diodes (LEDs) due to their bandgap uniformity and strong charge confinement effect. However, perovskite nanograin films prepared by the solution spin‐coating method are prone to produce massive defects due to the fast crystallization rate, leading to severe nonradiative recombination that greatly detracts the performance of LEDs. Therefore, regulating crystallization and minimizing defects plays a crucial role in the development of perovskite nanograins for high‐performance LEDs. Herein, a simple dual‐additive strategy is reported to manipulate the growth of high‐quality CsPbBr3‐based nanograin films. A multifunctional additive 5‐aminovaleric acid (5AVA) is introduced to slow down the crystallization rate of CsPbBr3, followed by the further addition of triphenylphosphine oxide (TPPO) to achieve effective synergistic passivation of defects, which can significantly enhance radiative recombination rate and reduce defects‐induced nonradiative recombination. Ultimately, based on the 5AVA and TPPO co‐modified CsPbBr3 nanograins, the perovskite LEDs are fabricated achieving a maximum external quantum efficiency (EQE) of 20.95% and an average EQE of approaching 20%, demonstrating excellent reproducibility. This work provides new insight into the crystallization regulation and defect passivation of perovskite nanograins and the further improvement of device performance.

Ultralong photoluminescence lifetime enables efficient tin halide perovskite solar cells

Lewis base additives typically undergo interactions with SnI2 to achieve effective defect passivation in lead-free perovskite films. In this work, the thiophene ring in 2-thiophenethylammonium chloride (TEACl) has coordination interactions with Sn2+ and the -NH3+ therein forms hydrogen bonds with I-. This facilitates the deposition of homogeneous and dense films with fewer defects during crystallization process. Otherwise, 2-pyridinethylammonium chloride (AEPCl) gives poorly perovskite films with high defect density because of the overly strong interaction with SnI2. As a result, the average photoluminescence life time of TEACl-passivated perovskite film was substantially increased to 22.04 ns, compared with the control film (5.15 ns) and the AEPCl-passivated film (3.55 ns). Ultimately, the target solar cell with TEACl passivation presented a power conversion efficiency of 13.24% and excellent shelf-stand stability with a 90% retaining of initial efficiency after 2000 h of aging in N2 atmosphere. This work sheds new light on the structural tailoring of Lewis base passivators for efficient defect passivation in lead-free tin halide perovskites.

Enhancing efficiency through surface passivation of carbon-based perovskite solar cells

Perovskite solar cells (PSCs) have made significant strides in power conversion efficiency (PCE), but their commercialization remains limited by stability issues. Additionally, the high cost of electrodes like gold necessitates the exploration of more affordable alternatives such as carbon (graphene). In this study, we present an approach that combines material dimensionality control and interfacial passivation using post-device treatment with phenethylammonium iodide (PEAI), an organic halide salt, to enhance the efficiency of carbon-based PSCs. Effective defect passivation is key to further improving the PCE and open-circuit voltage (VOC) of PSCs. Our results show that PEAI successfully passivates defects on the perovskite surface, significantly reducing non-radiative recombination. As a result, we achieved carbon-based PSCs with an impressive efficiency of 19.3%, demonstrating excellent stability under maximum power point tracking (MPPT) for over 900 h.

Innovative In Situ Passivation Strategy for High-Efficiency Sb2(S,Se)3 Solar Cells.

An effective defect passivation strategy is crucial for enhancing the performance of antimony selenosulfide (Sb2(S,Se)3) solar cells, as it significantly influences charge transport and extraction efficiency. Herein, a convenient and novel in situ passivation (ISP) technique is successfully introduced to enhance the performance of Sb2(S,Se)3 solar cells, achieving a champion efficiency of 10.81%, which is among the highest recorded for Sb2(S,Se)3 solar cells to date. The first principles calculations and the experimental data reveal that incorporating sodium selenosulfate in the ISP strategy effectively functions as an in situ selenization, effectively passivating deep-level cation antisite SbSe defect within the Sb2(S,Se)3 films and significantly suppressing non-radiative recombination in the devices. Space-charge-limited current (SCLC), photoluminescence (PL), and transient absorption spectroscopy (TAS) measurements verify the high quality of the passivated films, showing fewer traps and defects. Moreover, the ISP strategy improved the overall quality of the Sb2(S,Se)3 films, and fine-tuned the energy levels, thereby facilitating enhanced carrier transport. This study thus provides a straightforward and effective method for passivating deep-level defects in Sb2(S,Se)3 solar cells.

In Situ Synthesis of Br‐Rich CsPbBr3 Nanoplatelets: Enhanced Stability and High PLQY for Wide Color Gamut Displays

AbstractThis study presents the Br‐rich in situ synthesis of blue‐emitting 2D CsPbBr3 nanoplatelets (NPLs) with various Br/Pb ratios using ZnBr2 as a Br precursor to enhance Br ion adsorption significantly. This leads to effective passivation of surface defects, particularly Pb−Br bonds, by increasing the positive charge density around Pb atoms, thus creating a stable bonding environment and reducing defect formation. Consequently, the photoluminescence quantum yield (PLQY) improves from 31.15% for a Br/Pb ratio of 2 to 87.2% for a ratio of 6. NPLs with a Br/Pb ratio of 6 also exhibit longer lifetimes (16.69 ns) and slower bleach recovery dynamics, indicating fewer non‐radiative recombination pathways and effective exciton dynamics. Additionally, NPLs with the Br/Pb ratio of 6 demonstrated better thermal stability, with an activation energy of 124.3 meV, indicating stronger exciton binding. These NPLs also exhibited enhanced stability, with UV tolerance at 43.9% and water resistance at 23.8%, making them suitable for displays and lighting. Furthermore, Br‐passivated CsPbBr3 NPLs are used as blue emitters in prototype white LEDs, achieving a wide color gamut, 126.6% of the National Television Standards Committee and 94.5% of Rec. 2020, demonstrating their potential for high‐quality lighting and advanced display technologies.

(Invited) Progresses on Plasma Processing of Halide Perovskite Materials for Photovoltaic Applications

Metal halide perovskite (MHPs) solar cells represent a promising newcomer in the front of emerging photovoltaic technologies to address the dramatic energy crisis and climate change that we are facing. The exceptional properties of MHPs derive from their hybrid organic-inorganic nature, which allows also for low-cost and straightforward processing. Solar cells containing MHPs as absorbing layer have already achieved a power conversion efficiency of about 25,7 %, close to the efficiency of silicon-based devices. Nevertheless, a major limitation, still preventing the uptake of the technology, is related to the reduced stability of these materials when exposed to operative conditions, namely temperature, light, and moisture. Herein, an effective defect passivation of MHP surfaces is a key strategy to tackle both the stability and the enhancement of solar cell performances. Although many solution-based approaches 1 have been tested, we propose here an innovative use of plasma, as a solvent-free, scalable, and non-invasive promising strategy to boost MHP solar cells performances 2. As starting point we exposed the surface of Methylammonium Lead Iodide perovskite thin films to different plasma conditions implying the variation of power, gas, and treatment time, both for low-pressure (LP) and atmospheric pressure plasmas (APPs). The impact of Ar, , and LPPs on MAPbI3 optochemical properties and morphology was correlated to the performance of the photovoltaic devices and rationalized by density functional theory calculations3. Herein an interesting improvement in photoluminescence was observed for the Ar and treated films, while an improvement in PCE was observed only for the Ar treated device. This result was ascribed to the efficient removal of the superficial organic component, revealed through X-ray photoelectron spectroscopy (XPS), following suitable surface passivation by the electron transporting layer deposition. Following these results, we tested APP treatments, finding a milder morphological modification than LPP treatments but withstanding good surface passivation, as confirmed through the improved photoluminescence intensity, while the effect in terms of photovoltaic devices is still under investigations. Moving from these encouraging results, we applied plasma surface treatments to tin-based perovskite, finding a very interesting beneficial effect when reductive plasma conditions (forming gas) were used on FaSnI3 thin film.4 The collection of these results already show the great versatility and potential of plasma-based techniques for the intelligent modification of metal halide perovskite for solar energy conversion.

Repairing Interfacial Defects in Self-Assembled Monolayers for High-Efficiency Perovskite Solar Cells and Organic Photovoltaics through the SAM@Pseudo-Planar Monolayer Strategy.

Lately, carbazole-based self-assembled monolayers (SAMs) are widely employed as effective hole-selective layers (HSLs) in inverted perovskite solar cells (PSCs). Nevertheless, these SAMs tend to aggregate in solvents due to their amphiphilic nature, hindering the formation of a monolayer on the ITO substrate and impeding effective passivation of deep defects in the perovskites. In this study, a series of new SAMs including DPA-B-PY, CBZ-B-PY, POZ-B-PY, POZ-PY, POZ-T-PY, and POZ-BT-PY are synthesized, which are employed as interfacial repairers and coated atop CNph SAM to form a robust CNph SAM@pseudo-planar monolayer as HSL in efficient inverted PSCs. The CNph SAM@pseudo-planar monolayer strategy enables a well-aligned interface with perovskites, synergistically promoting perovskite crystal growth, improving charge extraction/transport, and minimizing nonradiative interfacial recombination loss. As a result, the POZ-BT-PY-modified PSC realizes an impressively enhanced solar efficiency of up to 24.45% together with a fill factor of 82.63%. Furthermore, a wide bandgap PSC achieving over 19% efficiency. Upon treatment with the CNph SAM@pseudo-planar monolayer, also demonstrates a non-fullerene organic photovoltaics (OPVs) based on the PM6:BTP-eC9 blend, which achieves an efficiency of 17.07%. Importantly, these modified PSCs and OPVs all show remarkably improved stability under various testing conditions compared to their control counterparts.

Multifaceted anchoring ligands for uniform orientation and enhanced cubic-phase stability of perovskite quantum dots

All-inorganic CsPbI3 perovskite quantum dots (PQDs) hold significant potential for next-generation photovoltaics due to their unique optoelectronic properties, and the surface-bound ligand playing a key role in the stability and functionality of CsPbI3 PQDs. Initially used long-chain ligands in PQDs synthesis stabilize the black phase but hinder charge transport when employed to solar cells, necessitating their replacement with shorter ones. However, this leads to the formation of surface defects and loss of tensile strain, resulting in the transition to the undesired orthorhombic phase (δ-phase) and compromising PQD solar cell performance. Therefore, developing a ligand exchange process that achieves the optimal balance between conductivity and stability in PQD solid films continues to be a significant challenge. To address these issues, we developed an efficient ligand-exchange process utilizing a multifaceted anchoring ligand, 2-thiophenemethylammonium iodide (ThMAI). The larger ionic size of ThMA+ compared to Cs+ facilitates the restoration of surface tensile strain in PQDs, while its thiophene and ammonium groups enable effective passivation of surface defects. Owing to these advantages, ThMAI-treated CsPbI3 PQD thin films exhibit improved carrier lifetime, uniform PQD orientation, and increased ambient stability. As a result, the ThMAI-treated CsPbI3 PQD solar cells demonstrate an improved power conversion efficiency (PCE) of 15.3 % and an enhanced device stability.

Understanding of Defect Passivation Effect on Wide Band Gap p-i-n Perovskite Solar Cell.

The wide band gap perovskite solar cells (PSCs) have attracted considerable attention for their great potential as top cells in high efficiency tandem cell application. However, the photovoltaic performance and stability of PSCs are constrained by nonradiative recombination, primarily stemming from defects within the bulk and at the interface of charge transport layer/perovskite and phase segregation. In this study, we systematically investigated the effects of 2-thiopheneethylammonium chloride (TEACl) on a wide band gap (∼1.67 eV) Cs0.15FA0.65MA0.20Pb(I0.8Br0.2)3 (CsFAMA) perovskite solar cell. TEACl was employed as a passivation layer between the perovskite and electron transport layer (ETL). With TEACl treatment, charged defects responsible for sub-band absorption and electrostatic potential fluctuation were effectively suppressed by the passivation of bulk defects. The incorporation of TEACl, which led to the formation of a TEA2PbX4/Perovskite (2D/3D) heterojunction, facilitated better band alignment and effective passivation of interface defects at the ETL/CsFAMA. Owing to these beneficial effects, the TEACl passivated PSC achieved a photo conversion efficiency (PCE) of 19.70% and retained ∼85% of initial PCE over ∼1900 h, surpassing the performance of the untreated PSC, which exhibited a PCE of 16.69% and retained only ∼37% of its initial PCE.

Moisture‐Induced High‐Quality Perovskite Film in Air for Efficient Solar Cells

The quality of perovskite light‐harvesting layer is known to be the most critical factor for the performance of perovskite solar cells (PSCs). Herein, a facile ambient air‐aging process (AAP, 20%–30% RH) is adopted to realize the fabrication of high‐quality Cs0.15FA0.75MA0.1PbI3 perovskite films, thereby upgrading device performance. We find that the perovskite crystallinity after AAP for 10 d is greatly intensified, with large grain size and preferred crystal orientation along (110) and (220) planes. Comparative studies on the Ag‐based devices employing the perovskite films upon exposing to different atmospheres, i.e., dry N2, dry O2, N2, and H2O (20%–30% RH) and ambient air (20%–30% RH), demonstrate that H2O molecules in air rather than O2 molecules induce an effective defect passivation that holds the multiple functions in enhancing the quality of perovskite film, inhibiting the nonradiative recombination, prolonging the carrier lifetime, and improving the energy level matching, etc. Moreover, the positive effect of H2O in ambient atmosphere on cell performance is irreversible and remains even if moisture escapes. Finally, the average power conversion efficiency (PCE) of device based on the AAP‐induced film is increased from 18.24 ± 1.49 to 21.34 ± 0.76, with the champion PCE up to 22.60%. Also, the device with AAP exhibits better moisture resistance capability. Herein, it offers a viable AAP‐induced route for the perovskite films with superb optoelectronic properties that can be subsequently extended to the design and construction of other photovoltaic devices for practical application.

Molecular packing regulation of dopant-free hole transport polymers for efficient perovskite solar cells

Spiro-OMeTAD is a primary hole transport material (HTM) employed in most state-of-the-art regular perovskite solar cells (PSCs). The essential reliance on hygroscopic ionic dopants to enhance the conductivity and mobility of Spiro-OMeTAD has dramatically compromised the stability of PSCs. Here, we demonstrated excellent photovoltaic performance of PSCs by developing two dopant-free polymers, namely L1 and L2, using thieno[3,2-b]thiophene as a building block. It is found that the n-hexyl-modified thiophene side chains endow the polymer L2 with favorable crystallinity, unique self-assembly behavior, and a preferable face-on stacking orientation. After the addition of a small amount (10 %) of PM6 to create a polymer alloy named LPA, the above properties were further improved, and the resulting film exhibited a distinct fibrous morphology, resulting in increased hole mobility and effective defect passivation. Consequently, PSCs employing LPA as a dopant-free HTM afforded a high efficiency of 23.81 %. Importantly, LPA-based PSCs exhibit significantly enhanced operational stability with a T80 lifetime of 1572 h at 55 °C. This work provides a crucial guideline for the design of dopant-free polymers, thereby advancing the practical application of PSCs.

Strategic Buried Defect Passivation of Perovskite Emitting Layers by Guanidinium Chloride for High-Performance Pure Blue Perovskite Light Emitting Diodes.

Perovskite light-emitting diodes (PeLEDs) show promise for high-definition displays due to their exceptional electroluminescent properties. However, the performance of pure blue PeLEDs is hindered by the unfavorable ionic behavior of halides and the presence of defective antisites in blue-emitting perovskite materials. An unstable buried interface between charge transport layers and the perovskite emitting layer is a major issue that limits carrier transport and recombination behavior in PeLEDs. In this study, effective buried defect passivation of pure blue perovskite emitting layers by introducing guanidinium chloride (GACl) as a bottom-passivating layer is demonstrated. The GACl bottom layer not only passivates the point defects present at the buried interface but also provides chloride anions to suppress ion migration and halide vacancy formation. Along with the defect passivation, GACl also enforces phase purity of 2D layered structure in the perovskite emitting layers to improve crystallinity and optoelectronic properties. As a result, the PeLEDs with high brightness (1200cd m-2) and excellent external quantum efficiency (6.61%) are achieved at a spectrally stable pure blue electroluminescence at 471nm (band width = 17.63nm). This study offers insights into the straightforward way for effective buried passivation for preparing high-performance PeLEDs.

Surface Passivation with Tailoring Organic Potassium Salt for Efficient FAPbI3 Perovskite Solar Cells and Modules

AbstractPassivating surface defects on perovskite films with tailored functional materials has emerged as one of the most effective strategies for achieving high‐performance perovskite solar cells (PSCs). Among existing material selections, potassium salts stand out for their effective passivation of defects surrounding perovskite grain boundaries. However, the widely used potassium salts are inorganic and only soluble in highly polar solvents, which limits their practical application for surface passivation. Herein, a novel organic potassium salt (KCFSO), with multiple organic functional groups and good solubility in low polar isopropanol, is reported to function as a post‐treatment agent for perovskite. Combined with experimental results and theoretical calculations, the formed multiple intermolecular interactions between KCFSO and perovskite are revealed to play a vital role in determining the defect passivation effect. Thus, the KCFSO‐modified film shows a more uniform surface potential distribution, dramatically decreased defect density, and improved charge transfer, leading to a champion power conversion efficiency (PCE) of 25.11%, and good stability for the derived PSCs. As a demonstration of scalability, the centimeter‐sized PSCs and 5 cm × 5 cm mini‐modules also demonstrate impressive PCEs of 24.17% and 20.18%, respectively. These findings provide insights into passivator design principles to achieve efficient and stable perovskite photovoltaics.

Interface Passivation of a Pyridine-Based Bifunctional Molecule for Inverted Perovskite Solar Cells.

Organic-inorganic hybrid perovskite solar cells (PSCs) have recently been demonstrated to be promising renewable harvesters because of their prominent photovoltaic power conversion efficiency (PCE), although their stability and efficiency still have not reached commercial criteria. Trouble-oriented analyses showcase that defect reduction among the grain boundaries and interfaces in the prepared perovskite polycrystalline films is a practical strategy, which has prompted researchers to develop functional molecules for interface passivation. Herein, the pyridine-based bifunctional molecule dimethylpyridine-3,5-dicarboxylate (DPDC) was employed as the interface between the electron-transport layer and perovskite layer, which achieved a champion PCE of 21.37% for an inverted MAPbI3-based PSC, which was greater than 18.64% for the control device. The mechanistic studies indicated that the significantly improved performance was mainly attributed to the remarkably enhanced fill factor with a value greater than 83%, which was primarily due to the nonradiative recombination suppression offered by the passivation effect of DPDC. Moreover, the promoted carrier mobility together with the enlarged crystal size contributed to a higher short-circuit current density. In addition, an increase in the open-circuit voltage was also observed in the DPDC-treated PSC, which benefited from the improved work function for reducing the energy loss during carrier transport. Furthermore, the DPDC-treated PSC showed substantially enhanced stability, with an over 80% retention rate of its initial PCE value over 300 h even at a 60% relative humidity level, which was attributed to the hydrophobic nature of the DPDC molecule and effective defect passivation. This work is expected not only to serve as an effective strategy for using a pyridine-based bifunctional molecule to passivate perovskite interfaces to enhance photovoltaic performance but also to shed light on the interface passivation mechanism.

Red-Emitting CsPbI3/ZnSe Colloidal Nanoheterostructures with Enhanced Optical Properties and Stability.

Producing heterostructures of cesium lead halide perovskites and metal-chalcogenides in the form of colloidal nanocrystals can improve their optical features and stability, and also govern the recombination of charge carriers. Herein, the synthesis of red-emitting CsPbI3/ZnSe nanoheterostructures is reported via an insitu hot injection method, which provides the crystallization conditions for both components, subsequently leading to heteroepitaxial growth. Steady-state absorption and photoluminescence studies alongside X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy analysis evidence on a type-I band alignment for CsPbI3/ZnSe nanoheterostructures, which exhibit photoluminescence quantum yield of 96% due to the effective passivation of surface defects, and an enhancement in carrier lifetime. Furthermore, the heterostructure growth of ZnSe domains leads to significant improvement in the stability of the CsPbI3 nanocrystals under ambient conditions and against thermal and UV irradiation stress.

Polyfluorinated Organic Diammonium Induced Lead Iodide Arrangement for Efficient Two-Step-Processed Perovskite Solar Cells.

The inefficient conversion of lead iodide to perovskite has become one of the major challenges in further improving the performance of perovskite solar cells fabricated by the two-step method. Herein, the discontinuous lead iodide layer realized by introduction of a polyfluorinated organic diammonium salt, octafluoro-([1,1'-biphenyl]-4,4'-diyl)-dimethanaminium (OFPP) iodide which does not form low-dimensional perovskites, can enable the satisfactory conversion of lead iodide into perovskite, leading to meliorated crystallinity and enlarged grains in the OFPP modulated perovskite (OFPP-PVK) film. Combined with the effective defect passivation, the OFPP-PVK films show enhanced charge mobility and suppressed charge recombination. Accordingly, the OFPP-based perovskite solar cells exhibit a champion efficiency of 24.76 % with better device stability. Moreover, a superior efficiency of 21.04 % was achieved in a large-area perovskite module (100 cm2). Our work provides a unique insight into the function of organic diammonium additive in boosting photovoltaic performance.