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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. [ABSTRACT FROM AUTHOR]

Photoelectrochemical (PEC) water splitting has attracted strong interest as sustainable technology by converting solar energy into hydrogen. The semiconductor photoelectrodes play an important role to increase the solar‐to‐hydrogen conversion efficiency. Bismuth vanadate (BiVO4) is an excellent candidate as a photoanode material for PEC water oxidation because of its visible light absorption, suitable band edge location, high stability and low cost. However, BiVO4 alone may undergo short carrier diffusion length, rapid recombination of photo‐induced charge carriers and photocorrosion. The heterojunction strategy established by combining two or more materials has provided an outstanding technique to address these issues. This Review focuses on recent important works with respect to BiVO4 heterojunction photoanodes for PEC water oxidation reactions, including interface junction and surface functional junction formation. Additionally, challenges faced and prospects for future research on BiVO4 heterojunction photoanodes in the field of solar‐to‐hydrogen conversion are proposed. [ABSTRACT FROM AUTHOR]

Antimony sulfide (Sb2S3) solar cells have attracted extensive attention in silicon‐based tandem solar cells. The performance of Sb2S3 devices fabricated by the vacuum method is limited by sulfur vacancies (VS) and surface oxide defects during high‐temperature processes. Herein, amorphous Sb2S3 film based on low‐temperature rapid thermal evaporation (RTE) technique is fabricated to overcome S loss. Moreover, a sulfur‐atmosphere recrystallization strategy is further developed to obtain high‐quality absorbers from the amorphous film. The element content of Sb2S3 film is completely in accord with the stoichiometric ratio (2:3), and the surface oxides are effectively suppressed, enhancing VOC and fill factor. Compared to the control directly crystallized film, the defect concentrations of the S‐recrystallized Sb2S3 film are reduced by 61%, exhibiting better uniformity and higher PN junction quality. Ultimately, the full‐inorganic Sb2S3 solar cells (FTO/TiO2/Sb2S3/Au) achieve an efficiency of 6.25%. The S‐atmosphere recrystallization process can effectively passivate bulk defects (VS and Sb2O3) and suppress recombination to improve device performance, which will provide new prospects for vacuum method‐based Sb2S3 thin film solar cells. [ABSTRACT FROM AUTHOR]

Inverted perovskite solar cells (PSCs) mainly adopt polytriarylamine (PTAA) for the hole transport material (HTM), which usually brings about inferior interfacial contact owing to their hydrophobicity, high‐lying highest occupied molecular orbital energy level, and deficiency of passivation groups. Herein, a series of donor–π–acceptor (D–π–A) type small molecules is demonstrated based on 2,2′:6′,2″‐terpyridine (TPy) as the acceptor moiety, benzene ring as the π‐linker, and incorporating various donors to act as HTMs. These TPy‐based molecules coated atop PTAA manipulate the energy level and surface wettability, but the incorporation of the phenoxazine (POZ) donor can be prominent for enhancing charge transport and defect passivation, thereby simultaneously addressing the above‐mentioned issues. The highest power conversion efficiency of 22.36% can be achieved with an open‐circuit voltage (VOC) of 1.15 V, a short‐circuit current density (JSC) of 23.96 mA cm−2, and a fill factor (FF) of 81.16% for the optimized POZ‐TPy‐modified device. Moreover, the power PCE of a large POZ‐TPy‐modified device (1.96 cm2) can still reach more than 21%. These results are among one of the highest efficiencies for inverted PSCs, indicating the enormous potential of POZ‐TPy HTM in future perovskite applications. [ABSTRACT FROM AUTHOR]

With the rapid development of perovskite solar cells, organic–inorganic hybrid Pb–Sn perovskite solar cells have attracted more and more attention in recent years due to their low toxicity, narrow bandgap and advantages of tandem solar cells. But for the present Pb–Sn mixed perovskite, the open circuit voltage is still at a relatively low level. Herein, phenyl–ethyl ammonium bromide (PEABr) was introduced into the perovskite structure by the method of composition regulation, and high quality and stable Pb–Sn perovskite MA0.5FA(0.5-x)PEAxPb0.5Sn0.5I(3-x)Brx films and devices were generated. Compared with the Pb–Sn mixed perovskite without component control treatment, the band structure of perovskite optimized by PEABr changes and the transport of charge carriers is promoted due to the introduction of PEA+ and Br−. In addition, the decomposition of perovskite caused by water and oxygen can be effectively slowed down due to the high stability and hydrophobic characteristics of the two-dimensional material PEA+. Finally, the efficiency of the Pb–Sn mixed perovskite device regulated by PEABr increased from 14.2% to 16.1%, and it could be maintained in the nitrogen environment for 14 days without significant efficiency attenuation, while the efficiency of the perovskite device without PEABr regulation decreased significantly. " [ABSTRACT FROM AUTHOR]

Carbon‐based perovskite solar cells (C‐PSCs) without hole transport layer have piqued the interest of researchers due to their low‐cost fabrication processes and exceptional stability. However, the efficiency of C‐PSCs lags far behind that of state‐of‐the‐art metal‐based devices, owing to an energy‐level mismatch and poor interfacial contact at the interface between carbon electrode and perovskite layer. Herein, a simple method for performing a solid‐phase reaction at the perovskite/carbon interface using a hot‐pressing process is presented. Unlike the solution processes commonly used in PSCs to obtain 2D halide perovskite layers, butylammonium iodide (BAI) is introduced into carbon electrodes, which are then hot pressed onto 3D perovskite in this work. During hot pressing, BAI in the carbon electrode reacts with the 3D perovskite layer to form a 2D perovskite layer at the perovskite/carbon interface through a solid‐phase reaction, resulting in a contiguous contact perovskite/carbon interface and better energy‐level alignment. Charge recombination at the perovskite/carbon interface is greatly reduced thanks to the seamless contact and the in situ formed 2D perovskite layer as passivation and electron blocking layer. This strategy results in a high power conversion efficiency of up to 16.86% and significantly improved the device stability for C‐PSCs. [ABSTRACT FROM AUTHOR]

Antimony chalcogenides (Sb2(SxSe1−x)3, 0 < x < 1) have recently gained popularity due to their excellent photoelectric properties. As a newcomer to thin‐film solar cells, the quality of the as‐prepared absorb layer remains the most difficult challenge, owing to its distinct crystal structure. Here, a solvent‐assisted hydrothermal deposition (SHD) technique is developed for direct deposition of high‐quality Sb2(S,Se)3 films; it is realized that the addition of ethanol can regulate the reaction kinetics by regulating the concentration of the Sb source during the deposition procedure. Impressively, under such conditions, the deposition rate of the target absorb layer slows dramatically, resulting in more suitable features, such as large grain size, smooth surface, and proper bandgap, which are beneficial for constructing high performance solar devices. More importantly, using this newly developed SHD strategy, the defect (SbS1) density of the prepared films decreases by more than one order of magnitude, which is believed to benefit carrier transport. As a result, Sb2(S,Se)3 solar cells based on the SHD strategy significantly improve fill factor and short‐circuit current density, yielding a high efficiency of 10.75%. This research offers fresh insights into how to make Sb2(S,Se)3 films and solar cells of higher quality. [ABSTRACT FROM AUTHOR]

The relatively large non‐radiative recombination energy loss (ΔE3) is the main source of energy losses in organic solar cells (OSCs). The energetic disorder plays a crucial role in non‐radiative energy losses; however, reducing the energetic disorder by modifying terminal groups has rarely been investigated. Herein, four acceptors, BTP‐ICB1F, BTP‐ICB2F, BTP‐ICB3F, and BTP‐ICBCF3, with fluorinated phenyl terminal groups are reported at identified substitution sites. The theoretical and experimental results show that this system possesses smaller energetic disorder than the generally‐used Y6 acceptor due to the strong electron polarization effect arising from tight, 3D molecular packing. Therefore, the PM6:BTP‐ICBCF3 combination achieves high efficiency of 17.8% with high open circuit voltage (VOC) of 0.93 V and ultralow ΔE3 of 0.18 eV, which is the smallest ΔE3 for the binary OSCs with power conversion efficiency (PCEs) over 17% reported to date. Lastly, using the ternary strategy by incorporating the BTP‐ICBCF3 acceptor into PM6:BTP‐eC9, a higher PCE of 18.2% is achieved with enhanced VOC. The results imply that introducing new terminal groups in acceptors is promising for reducing energetic disorder and energy losses. [ABSTRACT FROM AUTHOR]

The application of thin underdense hydrogenated amorphous silicon (a‐Si:H) films for passivation of crystalline Si (c‐Si) by avoiding epitaxy in silicon heterojunction (SHJ) solar cell technology has recently been proposed and successfully applied. Herein, the microstructure of such underdense a‐Si:H films, as used in our silicon heterojunction solar cell baseline, is investigated mainly by Raman spectroscopy, effusion, and secondary ion mass spectrometry. In H effusion experiments, a low‐temperature (near 400 °C) effusion peak which has been attributed to the diffusion of molecular H2 through a void network is seen. The dependence of the H effusion peaks on film thickness is similar as observed previously for void rich, low substrate‐temperature a‐Si:H material. Solar cells using underdense a‐Si:H as i1‐layer with a maximum efficiency of 24.1% are produced. The passivation quality of the solar cells saturates with increasing i1‐layer thickness. The fact that with such underdense material combined with a following high‐quality i2‐layer, instead of only high‐quality a‐Si:H with a low defect density direct on the c‐Si substrate, good passivation of c‐Si solar cells is achieved, which demonstrates that in the passivation process, molecular hydrogen plays an important role. [ABSTRACT FROM AUTHOR]

Exhibiting outstanding optoelectronic properties, antimony selenide (Sb2Se3) has attracted considerable interest and has been developed as a light absorber layer for thin‐film solar cells over the decade. However, current state‐of‐the‐art Sb2Se3 devices suffer from unsatisfactory "cliff‐like" band alignment and severe interface recombination loss, which deteriorates device performance. In this study, the heterojunction interface of an Sb2Se3 solar cell is improved by introducing effective aluminum (Al3+) cation into the CdS buffer layer. Then, the energy band alignment of Sb2Se3/CdS:Al heterojunction is modified from a "cliff‐like" structure to a "spike‐like" structure. Finally, heterojunction interface engineering suppresses recombination losses and strengthens carrier transport, resulting in a high efficiency of 8.41% for the substrate‐structured Sb2Se3 solar cell. This study proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism, paving a bright avenue to overcome the efficiency bottleneck of Sb2Se3 thin‐film solar cells. [ABSTRACT FROM AUTHOR]

Hole transporting materials (HTMs) are imperative for promoting the development of perovskite solar cells (PSCs). Herein, three isomers of RQ4, RQ5, and RQ6 are constructed by methylthio (‐SMe) group in the para, meta, and adjacent sites of terminal benzene on the side‐chain of carbazole‐arylamine derivatives based HTMs, and investigated by means of the theoretical simulation and experimental characterization. As a result of the theoretical simulation, the isomeric HTMs of RQ4‐RQ6 exhibit appropriate highest occupied molecular orbital /lowest unoccupied molecular orbital energy levels and good optical properties. However, by comparison with RQ4 and RQ5, a better planar configuration and closer molecular stacking for RQ6 may be beneficial to promote the hole coupling, interface interaction, and charge transfer at perovskite/HTMs interface. In order to verify the accuracy of the theoretical model, the designed RQ4‐RQ6 are synthesized to be used to assemble PSCs devices. In comparison to isomers RQ4 (20.07%) and RQ5 (18.18%) based devices, the RQ6 based devices has higher power conversion efficiency of 21.03% because of its high hole mobility, the film formation ability, and large charge transfer at perovskite/HTMs interface. The experimental results confirm the reliability of the theoretical simulation and provide an effective strategy to obtain potential HTMs through isomerization of side‐chain functional groups. [ABSTRACT FROM AUTHOR]

Compared to their inorganic counterparts, organic optoelectronic devices receive considerable attention due to their lower cost, mechanical flexibility, bandgap engineering, and solution processability. In particular, achieving sustainability in solar cells and light emitting devices is an important milestone in the development of green electronics. This has facilitated a close collaboration between different technological fields, opening new ways for low‐cost production and application of biomaterials. Recently, biomass materials, mainly derived from plants, animals and microorganisms, have emerged as effective candidates to modify the interfacial properties, and thus enhance the performance, lifetime, and stability of organic solar cells (OSCs), perovskite solar cells (PVSCs), and organic light‐emitting diodes (OLEDs). Compared to the commonly used synthetic interfacial materials, the use of biomass interlayer materials (BIMs) is still in its embryonic stages; however, their nontoxicity, biorelevance, sustainability, special proton conductivity, and rich functional groups are stimulating researchers around the globe to fabricate novel devices with improved efficiency. Herein, a comprehensive review of BIMs and their importance in next‐generation optoelectronic devices is provided. A well‐targeted comparison between the electrical and physical properties of different BIMs is provided, and how such characteristics improve the performance of three key optoelectronic devices: OSCs, PVSCs and OLEDs, is discussed. [ABSTRACT FROM AUTHOR]

Ming Cheng Thiophene and oligothiophenes have outstanding electronic properties, especially their electron-rich nature, which endows them with good interfacial contacts with perovskite layers, and hence makes them ideal building blocks for hole-transport materials (HTMs). In the current work, we successfully synthesized two novel HTMs with terthienyl (TTP) as the core structure and triphenylamine or 4,40- dimethoxydiphenylamine as the end-capping groups, and termed them THP-1 and THP-2, respectively. Compared with THP-2, THP-1 exhibited a more suitable energy level and appropriate three-dimensional molecular structure, leading to better optoelectronic properties for THP-1. After optimization, PSCs based on THP-1 as the HTM achieved a power conversion efficiency (PCE) of as high as 20.47%, much higher than that of THP-2 (17.16%), and comparable to that of the control device based on spiro- OMeTAD (20.28%). Furthermore, the THP-1-based device maintained 71.5% of its initial efficiency, while the THP-2-based device and control device maintained only, respectively, 22.3% and 43.3% of their initial efficiency values, after 840 h aging tests at room temperature and under 30-45% relative humidity conditions, indicative of the excellent stability of the THP-1-based device. [ABSTRACT FROM AUTHOR]

Antimony sulfide (Sb2S3) with a 1D molecular structure has strong bending characteristics, showing great application potential in flexible devices. Herein, the flexible substrate-structured Sb2S3 solar cells is developed and improve device performances by the back interface selenization. The high-quality Sb2S3 film with an optimal thickness of 1.8 μm, ensuring efficient spectra utilization, is deposited on flexible Mo foils by the rapid thermal evaporation technique. To solve the issues of back interfacial recombination and charge transport, the 20 nm MoSe2 layer between Sb2S3 film and Mo foil is fabricated by substrate selenization in the tube furnace. Further investigations indicate that the MoSe2 layer improves the interfacial energy band alignments and induces the [hk1] orientation of Sb2S3 film, thereby passivating defects and enhancing the carrier transport capacity. The flexible solar cell in the structure of Mo foil/MoSe2/Sb2S3/CdS/ITO/Ag, exhibiting good flexibility to stand thousands of bending, achieves an efficiency of 3.75%, which is the highest for Sb2S3 devices in substrate configuration. The presented flexible structure and back interfacial selenization study will provide new prospects for inorganic Sb2S3 thin film solar cells. [ABSTRACT FROM AUTHOR]

Antimony selenosulfide (Sb2(S,Se)3) has been emerging as a promising light absorber in the past few years owing to tunable bandgap (1.1–1.7 eV), high absorption coefficient (>105 cm−1) and excellent phase and environmental stability. However, the efficiency of Sb2(S,Se)3 solar cells lags far behind the Shockley–Queisser limit. One of the critical obstacles originates from various extrinsic and intrinsic defects. They mostly locate in the deep energy levels and are prone to form recombination centers, inhibiting the improvement of device performance. Herein, surface post‐treatment via potassium iodide is introduced to fabricate high‐quality Sb2(S,Se)3 films and solar cells. The surface post‐treatment not only manipulates the crystal growth process to form compact films with larger grain size but also forms better band alignment and inhibits the formation of deep‐level defects antimony antisite (SbSe), thus improving the quality of heterojunction. Consequently, the resultant Sb2(S,Se)3 solar cells achieve a champion power conversion efficiency of 9.22%. This study provides a new strategy of passivating deep‐level intrinsic defects via surface post‐treatment for high‐efficiency Sb2(S,Se)3 solar cells. [ABSTRACT FROM AUTHOR]

The accumulation of organic dyes in water and their consequent detrimental effect to ecological environment have attracted worldwide extensive attention. It is urgent to develop rapid and efficient method to degrade organic dyes. In this paper, an efficient CdZnS/SnS2/SnO2 heterojunction is successfully prepared by sequential template approach and hydrothermal method. Comparison with CdZnS and SnS2/SnO2, the heterogeneous structure of CdZnS/SnS2/SnO2 greatly enhances the photocatalytic degradation ability of Rhodamine B (RhB). The apparent reaction rate of CdZnS/SnS2/SnO2 heterostructure is around 12.71 and 16.69 times higher than those of SnS2/SnO2 and CdZnS, respectively, reaching 0.0267 min−1. After CdZnS/SnS2/SnO2 photocatalysis of RhB solution, the BOD/COD ratio increases from 0.168 to 0.725, indicating that the biodegradability is greatly improved. It has been proved that ⋅OH, ⋅O2−, h+ and e− are the main active species involved in the degradation process. In addition, the CdZnS/SnS2/SnO2 exhibits good stability and reusability, with little change in the photocatalytic activity after five cycles. Its superior removal activity is mainly due to the formation of heterojunction improved light harvesting and enhanced separation efficiency. This work provides a new insight for photocatalytic degradation of organic dye wastewater by solar light. [ABSTRACT FROM AUTHOR]

Antimony sulfide (Sb2S3) is emerging as a promising light harvesting material owing to its brilliant photoelectric property. However, the performance of Sb2S3‐based solar cells is partly limited by serious back contact interface recombination and hole transportation resistance. High‐efficiency Sb2S3 devices typically use Spiro‐OMeTAD and/or Au as back contact materials, but their stability and cost are a concern. In this sense, a surface modification scheme by lithium‐doping is first introduced for Sb2S3 via a facile molten salt method. The ions in the molten state have high mobility and activity, enabling doping reactions to complete within a short time. The lithium‐doped Sb2S3 thin film has a smooth and well‐bonded surface, preferred (hk1) orientations, and an upshifted valence band maximum (VBM), which favors the hole extraction. Finally, a device using carbon as an electrode, which is more than a dozen times cheaper than gold, raises the short‐circuit current density (JSC) from 12.35 to 14.40 mA cm−2, and the power conversion efficiency (PCE) from 4.47% to 6.16%. This is among the highest PCE reported for full‐inorganic Sb2S3 solar cells, which demonstrates a facile interface modification technique via molten alkali salt to improve the performance of Sb2S3 solar cells. [ABSTRACT FROM AUTHOR]

Highly crystalized perovskite film with smooth surface is of great importance to obtain high photovoltaic performances. Herein, UV irradiation is applied to the perovskite films during their thermal annealing process. It is revealed that UV irradiation treatment can largely improve perovskite crystallization and reduce defects. This greatly improves power conversion efficiency (PCE) and environmental stability of the resulted solar cells (ITO/SnO2/perovskite/Spiro‐OMeTAD/Au). By combining CH3O‐PEAI surface passivation, an outstanding PCE of 23.24% is achieved. [ABSTRACT FROM AUTHOR]

Lead leakage from perovskite solar cells (PSCs) leads to device failure and environment contamination. Here, these issues are solved with a sodium phosphate (Na3PO4)‐modified tin(IV) dioxide (SnO2) layer that simultaneously boosts the device performance and captures most of dissolved lead in water. Phosphate incorporation improves charge transfers and passivates the buried perovskite interface, leading to highly improved device efficiency up to 23% with negligible hysteresis. More importantly, the phosphatized SnO2 layer shows high lead‐adsorption capacity with a sequestration efficiency of 79.6% due to the numerous anchor sites of oxygen lone pairs, converting dissolved lead into insoluble compounds in water. This study presents a facile protocol of efficient and sustainable perovskite photovoltaics upon future commercialization. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskites have emerged as versatile materials for various electronic and optoelectronic devices such as diodes, solar cells, photodetectors, and sensors due to their interesting properties of high absorption coefficient in the visible regime, tunable bandgap, and high power conversion efficiency. Recently, metal‐free organic perovskites have also emerged as a particular class of perovskites materials for piezoelectric applications. This broadens the chemical variety of perovskite structures with good mechanical adaptability, light‐weight, and low‐cost processability. Despite these achievements, the fundamental understanding of the underlying phenomenon of piezoelectricity in metal‐free perovskites is still lacking. Therefore, this perspective emphasizes the overview of piezoelectric properties of metal‐halide, metal‐free perovskites, and their recent progress which may encourage material designs to enhance their applicability towards practical applications. Finally, challenges and outlooks of piezoelectric metal‐free perovskites are highlighted for their future developments. [ABSTRACT FROM AUTHOR]

The quality of perovskite layers has a great impact on the performance of perovskite solar cells (PSCs). However, defects and related trap sites are generated inevitably in the solutionprocessed polycrystalline perovskite films. It is meaningful to reduce and passivate the defect states by incorporating additive into the perovskite layer to improve perovskite crystallization. Here an environmental friendly 2D nanomaterial protonated graphitic carbon nitride (p-g-C3N4) was successfully synthesized and doped into perovskite layer of carbon-based PSCs. The addition of p-g-C3N4 into perovskite precursor solution not only adjusts nucleation and growth rate of methylammonium lead tri-iodide (MAPbI3) crystal for obtaining flat perovskite surface with larger grain size, but also reduces intrinsic defects of perovskite layer. It is found that the p-g-C3N4 locates at the perovskite core, and the active groups -NH2/NH3 and NH have a hydrogen bond strengthening, which effectively passivates electron traps and enhances the crystal quality of perovskite. As a result, a higher power conversion efficiency of 6.61% is achieved, compared with that doped with g-C3N4 (5.93%) and undoped one (4.48%). This work demonstrates a simple method to modify the perovskite film by doping new modified additives and develops a low-cost preparation for carbon-based PSCs. [ABSTRACT FROM AUTHOR]

Optimization of a new system for organic solar cells is a multiparametric analysis problem that requires substantial efforts in terms of time and resources. The strong microstructure‐dependent performance of polymer:polymer cells makes them particularly difficult to optimize, or to translate previous knowledge from spin coating into more scalable techniques. In this work, the photovoltaic performance of blade‐coated devices was studied based on the promising polymer:polymer system PBDB‐T and PF5‐Y5 as donor and acceptor, respectively. Using the recently developed high‐throughput methodology, the system was optimized for multiple variables, including solvent system, active layer composition, ratio, and thickness, among others, by fabricating more than 500 devices with less than 24 mg of each component. As a result, the power conversion efficiency of the blade‐coated devices varied from 0.08 to 6.43 % in the best device. The performed statistical analysis of the large experimental data obtained showed that solvent selection had the major impact on the final device performance due to its influence on the active layer microstructure. As a conclusion, the use of the plot of the device efficiency in the Hansen space was proposed as a powerful tool to guide solvent selection in organic photovoltaics. [ABSTRACT FROM AUTHOR]

Structural defects are ubiquitous for polycrystalline perovskite films, compromising device performance and stability. Herein, a universal method is developed to overcome this issue by incorporating halide perovskite quantum dots (QDs) into perovskite polycrystalline films. CsPbBr3 QDs are deposited on four types of halide perovskite films (CsPbBr3, CsPbIBr2, CsPbBrI2, and MAPbI3) and the interactions are triggered by annealing. The ions in the CsPbBr3 QDs are released into the thin films to passivate defects, and concurrently the hydrophobic ligands of QDs self‐assemble on the film surfaces and grain boundaries to reduce the defect density and enhance the film stability. For all QD‐treated films, PL emission intensity and carrier lifetime are significantly improved, and surface morphology and composition uniformity are also optimized. Furthermore, after the QD treatment, light‐induced phase segregation and degradation in mixed‐halide perovskite films are suppressed, and the efficiency of mixed‐halide CsPbIBr2 solar cells is remarkably improved to over 11% from 8.7%. Overall, this work provides a general approach to achieving high‐quality halide perovskite films with suppressed phase segregation, reduced defects, and enhanced stability for optoelectronic applications. [ABSTRACT FROM AUTHOR]