Ligang Yuan

This study investigates the impact of chloride, bromide, or diiodooctane on the perovskite ink wetting properties, as well as the storage of the substrates. All of the inner layer is inkjet‐printed and annealed at low temperature. This leads to the successful demonstration of 10.7% efficient chlorine‐doped methylammonium lead iodide solar cells.

Considering the recent advances in the fundamental understanding of perovskite devices as well as in the demonstration of larger stability under working conditions, specific attention has still to be paid for their processing for low‐cost applications. Here, the successful demonstration of 10.7% efficient chlorine‐doped methylammonium lead iodide (CH₃NH₃PbI_3‐xCl_x) solar cells based on a fully inkjet‐printed processed under ambient conditions and at low temperature (<90 °C) is reported. A huge hysteresis is observed and the efficiency drops down to 6.4% for the forward scan. The Owens–Wendt–Rabel and Kaelble model is applied to investigate the impact of chloride, bromide, or diiodooctane on the perovskite ink wetting properties. A low surface energy of the substrate provokes dewetting during the perovskite printing. The use of chlorine or bromide tends to increase the wettability of the perovskite ink, improving the impregnation of the ink in porous materials. This work shows the critical importance of properly storing these substrates prior to active layer deposition, in order to produce homogenous layers by inkjet‐printing. The successful printing of all inner layers, excluding bottom and top electrodes, in ambient atmosphere is an additional step toward their expected development at a larger scale by the printed electronic industry.

Two different charge recombination mechanisms are distinguished in perovskite solar devices based on electron selective layers of different structural and morphological properties. The impact of the interfacial and bulk recombination processes on the photovoltaic performance and hysteresis found in the IV curve measurements is analyzed.

Abstract

Herein, the preparation of 1D TiO₂ nanocolumnar films grown by plasma‐enhanced chemical vapor deposition is reported as the electron selective layer (ESL) for perovskite solar devices. The impact of the ESL architecture (1D and 3D morphologies) and the nanocrystalline phase (anatase and amorphous) is analyzed. For anatase structures, similar power conversion efficiencies are achieved using an ESL either the 1D nanocolumns or the classical 3D nanoparticle film. However, lower power conversion efficiencies and different optoelectronic properties are found for perovskite devices based on amorphous 1D films. The use of amorphous TiO₂ as electron selective contact produces a bump in the reverse scan of the current–voltage curve as well as an additional electronic signal, detected by impedance spectroscopy measurements. The dependence of this additional signal on the optical excitation wavelength used in the IS experiments suggests that it stems from an interfacial process. Calculations using a drift‐diffusion model which explicitly considers the selective contacts reproduces qualitatively the main features observed experimentally. These results demonstrate that for a solar cell in which the contact is working properly the open‐circuit photovoltage is mainly determined by bulk recombination, whereas the introduction of a “bad contact” shifts the balance to surface recombination.

A diboron‐assisted strategy for tuning interfacial defects in formamidinium‐iodide‐based perovskite solar cells is demonstrated to decompose the unreacted organic‐halide species at the surface by coating B₂Cat₂ on top of the perovskite films, which can suppress the nonradiative recombination loss and boost power conversion efficiency. This approach paves a new way for mitigating defects and improving device performance.

Abstract

Metal halide perovskite films are endowed with the nature of ions and polycrystallinity. Formamidinium iodide (FAI)‐based perovskite films, which include large cations (FA) incorporated into the crystal lattice, are most likely to induce local defects due to the presence of the unreacted FAI species. Here, a diboron‐assisted strategy is demonstrated to control the defects induced by the unreacted FAI both inside the grain boundaries and at the surface regions. The diboron compound (C₁₂H₁₀B₂O₄) can selectively react with unreacted FAI, leading to reduced defect densities. Nonradiative recombination between a perovskite film and a hole‐extraction layer is mitigated considerably after the introduction of the proposed approach and charge‐carrier extraction is improved as well. A champion power conversion efficiency of 21.11% is therefore obtained with a stabilized power output of 20.83% at the maximum power point for planar perovskite solar cells. The optimized device also delivers negligible hysteresis effect under various scanning conditions. This approach paves a new way for mitigating defects and improving device performance.

In order to reduce the cost of hole transporting materials (HTMs) for perovskite solar cells, the amide‐bond is introduced in the backbone resulting in a straightforward synthesis. Despite the lack of conjugation, the here presented HTM (EDOT‐Amide‐TPA) outperforms state‐of‐the‐art materials in performance, showing over 20% power conversion efficiency, and stability, which is assigned to the unique properties of the amide‐bond.

Abstract

State‐of‐the‐art perovskite‐based solar cells employ expensive, organic hole transporting materials (HTMs) such as Spiro‐OMeTAD that, in turn, limits the commercialization of this promising technology. Herein an HTM (EDOT‐Amide‐TPA) is reported in which a functional amide‐based backbone is introduced, which allows this material to be synthesized in a simple condensation reaction with an estimated cost of <$5 g⁻¹. When employed in perovskite solar cells, EDOT‐Amide‐TPA demonstrates stabilized power conversion efficiencies up to 20.0% and reproducibly outperforms Spiro‐OMeTAD in direct comparisons. Time resolved microwave conductivity measurements indicate that the observed improvement originates from a faster hole injection rate from the perovskite to EDOT‐Amide‐TPA. Additionally, the devices exhibit an improved lifetime, which is assigned to the coordination of the amide bond to the Li‐additive, offering a novel strategy to hamper the migration of additives. It is shown that, despite the lack of a conjugated backbone, the amide‐based HTM can outperform state‐of‐the‐art HTMs at a fraction of the cost, thereby providing a novel set of design strategies to develop new, low‐cost HTMs.

Perovskite solar cells produced by roll‐to‐roll (R2R) slot die coating on flexible substrates at ambient atmosphere from nontoxic solvents demonstrate an average stabilized efficiency of 12%, with the best value of 13.5%. This study is the first public demonstration of R2R slot die coating of perovskites on 30 cm wide substrates with the deposition and drying speed of 3–5 m min⁻¹.

Abstract

The feasibility of upscaling the perovskite solar cells technologies to high volume production using roll‐to‐roll (R2R) slot die coating is demonstrated in this study. Perovskite solar cells are produced by R2R slot die coating on flexible substrates with a width of 30 cm and the web speed of 3–5 m min⁻¹. R2R deposition of the electron transport layer and perovskite is performed at ambient atmosphere from nontoxic solvents compatible with industrial manufacturing. The average stabilized power conversion efficiency of the devices made on different areas of the foil is 12%, with the best value of 13.5%. The demonstrated achievement is an important milestone and a big solid step toward future commercialization of perovskite‐based solar cells technologies.

The performance of ZnO interfacial layers doped with metal–quinoline (Q) groups is demonstrated in organic solar cells (OSCs). The light absorption of the photoactive layer is improved upon incorporating a doped interfacial layer into OSCs. The power conversion efficiency of OSC with GaQ:ZnO interfacial layer can be substantially increased attributed to an improved exciton dissociation rate, enhanced carrier transport, and a lower work function.

Abstract

Optimizing the function of interfacial materials between the photoactive layer and the metal cathode is critical for realizing high‐efficiency organic solar cells (OSCs). The charge‐collecting layer requires a material with an excellent electrical property to improve the charge collection efficiency and decrease the leakage current that increases the power conversion efficiency (PCE). In this study, the performance of sol–gel‐derived modified cathode interfacial (ZnO) layers, prepared by an appropriate doping of metal (M = Al, Ga, and Mn)quinoline (Q) groups in OSCs, is demonstrated and evaluated. The light absorption of the photoactive layer is improved upon incorporating an interfacial layer into the OSCs. The PCE of the GaQ:ZnO‐based device is higher than that of the AlQ:ZnO and MnQ:ZnO‐based devices, attributed to an improved exciton dissociation rate, enhanced carrier transport, greater electron mobility, and a lower work function. Incorporating a GaQ:ZnO interfacial layer into a thieno[3,4‐b]thiophene/benzodithiophene:[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PTB7:PC₇₁BM) OSC increases the PCE from 7.51% to 8.44%, and incorporating it into a poly[[2,6′‐4‐8‐di(5‐ethylhexylthienyl)benzo[1,2‐b:3,3‐b]dithiophene][3‐fluoro‐2[(2‐ethylhexyl) carbonyl]thieno[3,4‐b]thiophenediyl:[6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PTB7‐Th:PC₇₁BM) (PTB7‐Th:PC₇₁BM) OSC increases the PCE from 8.11% to 9.02%.

Semiconducting carbon nanotubes incorporated as an anode interlayer in PbS quantum dot solar cells stabilize the device performance. Devices with carbon nanotubes retained 85% of the initial performance after 100 h exposure to simulated solar light in ambient condition. While in the same conditions, the reference devices show less than 20% of their initial efficiency.

Abstract

Semiconducting single‐walled carbon nanotubes (s‐SWNTs) are used as a protective interlayer between the lead sulfide colloidal quantum dot (PbS CQD) active layer and the anode of the solar cells (SCs). The introduction of the carbon nanotubes leads to increased device stability, with 85% of the initial performance retained after 100 h exposure to simulated solar light in ambient condition. This is in sharp contrast with the behavior of the device without s‐SWNTs, for which the photoconversion efficiency, the open circuit voltage, the short‐circuit current, and the fill factor all experiencing a sharp decrease. Therefore, the inclusion of s‐SWNT as interlayer in CQD SCs, give rise to SCs of identical efficiency (above 8.5%) and prevents their performance degradation.

The ZnO:PEOz hybrid electron‐collecting buffer layers with distinctive (wrinkled) nanocrater structures, which are generated by low‐temperature processes (120–130 °C), can effectively improve the efficiency of polymer:nonfullerene solar cells.

Abstract

Here distinctive nanocrater structures generated in the low temperature‐processed hybrid electron‐collecting buffer layers (h‐ECBLs), consisting of zinc oxide (ZnO) and poly(2‐ethyl‐2‐oxazoline) (PEOz), for high efficiency inverted‐type polymer:nonfullerene solar cells are reported. The ZnO:PEOz h‐ECBLs are prepared from their precursor films via thermal annealing at 110–130 °C, which is far lower than conventional condition (200 °C). Results show that the power conversion efficiency (PCE) of solar cells is noticeably improved by introducing the h‐ECBLs with 6 wt% PEOz but turned down at higher PEOz contents irrespective of the annealing temperature (from 9.25% to 11.41% at 120 °C and from 10.19% to 12.03% at 130 °C). The improved PCE is explained by the increased electron mobility in the h‐ECBLs (6 wt%) due to the reduced oxygen deficiency of ZnO by the PEOz components as well as the generated nanocrater (wrinkled at 120 °C) structures leading to the enhanced interfacial area and contact with the active layers.

Nanopatterned fluorine‐doped tin oxide (FTO) substrates are prepared via self‐assembly and sphere lithography technique. Through analyzing the measurement and simulation results, the light absorption of perovskite layer is enhanced by diffraction effect and the charge transfer is improved by increasing the interfaces of FTO/TiO₂/perovskite. Compared with planar perovskite solar cell, the power conversion efficiency is improved from 14.21% to 17.85%.

Abstract

In this study, a CH₃NH₃PbI₃‐based perovskite solar cell (PSC) with high power conversion efficiency (PCE) has achieved by incorporating a nanopatterned fluorine‐doped tin oxide (FTO) substrate (NPFS). This NPFS‐PSC is prepared with different structural depths (100, 150, and 200 nm) using both self‐assembly and sphere lithography techniques. As determine through the optical and electrical analysis of different PSC devices, the NPFS‐PSCs not only display the enhanced light absorption (due to the 2D diffraction grating) but also improve the electron collection efficiency by increasing the FTO/electron transport layer (ETL) and ETL/perovskite effective interface area. Compared to a planar PSC, the photocurrent density of the 200 nm etched NPFS‐PSC is enhanced from 19.27 to 23.81 mA cm⁻² leading to an increase in the PCE from 14.21% to 17.85%. These results indicate that introducing the NPFS into the TiO₂‐based PSC can improve both light absorption ability and electron extraction and, therefore, represents a novel, promising, high‐performance photovoltaic device.

A tandem organic photovoltaic cell combining a nonfullerene‐acceptor‐based ternary cell with a fullerene small‐molecule binary subcell is reported. The cell combines vacuum‐ and solution‐deposited layers, achieving a power conversion efficiency of 15.4%.

Abstract

The paucity of near‐infrared (NIR) organic materials with high absorption at long wavelengths, combined with large diffusion lengths and charge mobilities, is an impediment to progress in achieving high‐efficiency organic tandem solar cells. Here a subcell is employed within a series tandem stack that comprises a solution‐processed ternary blend of two NIR‐absorbing nonfullerene acceptors and a polymer donor combined with a small‐molecular‐weight, short‐wavelength fullerene‐based subcell grown by vacuum thermal evaporation. The ternary cell achieves a power conversion efficiency of 12.6 ± 0.3% with a short‐circuit current of 25.5 ± 0.3 mA cm⁻², an open‐circuit voltage of 0.69 ± 0.01 V, and a fill factor of 0.71 ± 0.01 under 1 sun, AM 1.5G spectral illumination. The success of this device is a result of the nearly identical offset energies between the lowest unoccupied molecular orbitals (LUMOs) of the donors with the highest occupied molecular orbital (HOMO) of the acceptor, resulting in a high open‐circuit voltage. A tandem structure with an antireflection coating combining these subcells demonstrates a power conversion efficiency of 15.4 ± 0.3%.

Efficient nonfullerene organic solar cells (OSCs) are realized by combining a donor polymer, PffBT2T‐TT, and a small‐molecular acceptor, O‐IDTBR, which have identical bandgaps and close energy levels. Despite the small energy offsets for both hole and electron transfer, this system can still achieve efficient charge separation and a high efficiency of 10.4%.

Abstract

State‐of‐the‐art organic solar cells (OSCs) typically suffer from large voltage loss (V _loss) compared to their inorganic and perovskite counterparts. There are some successful attempts to reduce the V _loss by decreasing the energy offsets between the donor and acceptor materials, and the OSC community has demonstrated efficient systems with either small highest occupied molecular orbital (HOMO) offset or negligible lowest unoccupied molecular orbital (LUMO) offset between donors and acceptors. However, efficient OSCs based on a donor/acceptor system with both small HOMO and LUMO offsets have not been demonstrated simultaneously. In this work, an efficient nonfullerene OSC is reported based on a donor polymer named PffBT2T‐TT and a small‐molecular acceptor (O‐IDTBR), which have identical bandgaps and close energy levels. The Fourier‐transform photocurrent spectroscopy external quantum efficiency (FTPS‐EQE) spectrum of the blend overlaps with those of neat PffBT2T‐TT and O‐IDTBR, indicating the small driving forces for both hole and electron transfer. Meanwhile, the OSCs exhibit a high electroluminescence quantum efficiency (EQE_EL) of ≈1 × 10⁻⁴, which leads to a significantly minimized nonradiative V _loss of 0.24 V. Despite the small driving forces and a low V _loss, a maximum EQE of 67% and a high power conversion efficiency of 10.4% can still be achieved.

Phase‐transfer catalyzed colloidal‐quantum‐dot (CQD) inks are developed with the aid of a neutral donor ligand. This enables graded IR CQD solar cells exhibiting the highest power conversion efficiency (PCE) of 12.3% using large‐bandgap (E _g ≈ 1.3 eV) CQDs. By using small‐E _g (1 eV) CQDs, a new record PCE of +5.0% is demonstrated on top of a perovskite (E _g ≈ 1.58 eV) front filter.

Abstract

The best‐performing colloidal‐quantum‐dot (CQD) photovoltaic devices suffer from charge recombination within the quasi‐neutral region near the back hole‐extracting junction. Graded architectures, which provide a widened depletion region at the back junction of device, could overcome this challenge. However, since today's best materials are processed using solvents that lack orthogonality, these architectures have not yet been implemented using the best‐performing CQD solids. Here, a new CQD ink that is stable in nonpolar solvents is developed via a neutral donor ligand that functions as a phase‐transfer catalyst. This enables the realization of an efficient graded architecture that, with an engineered band‐alignment at the back junction, improves the built‐in field and charge extraction. As a result, optimized IR CQD solar cells (E _g ≈ 1.3 eV) exhibiting a power conversion efficiency (PCE) of 12.3% are reported. The strategy is applied to small‐bandgap (1 eV) IR CQDs to augment the performance of perovskite and crystalline silicon (cSi) 4‐terminal tandem solar cells. The devices show the highest PCE addition achieved using a solution‐processed active layer: a value of +5% when illuminated through a 1.58 eV bandgap perovskite front filter, providing a pathway to exceed PCEs of 23% in 4T tandem configurations with IR CQD PVs.

The influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation is studied. The smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current. This work reveals the strong dependence of the surface condition of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties.

Abstract

Despite the remarkable progress of optoelectronic devices based on hybrid perovskites, there are significant drawbacks, which have largely hindered their development as an alternative of silicon. For instance, hybrid perovskites are well‐known to suffer from moisture instability which leads to surface degradation. Nonetheless, the dependence of the surface effect on the moisture stability and optoelectronic properties of hybrid perovskites has not been fully investigated. In this work, the influence of the surface effect of 2D layered perovskites before and after mechanical exfoliation, representing rough and smooth surfaces of perovskite crystals, are studied. It is found that the smooth 2D perovskite is less sensitive to ambient moisture and exhibits a considerably low dark current, which outperforms the rough perovskites by 23.6 times in terms of photodetectivity. The superior moisture stability of the smooth perovskites over the rough perovskites is demonstrated. Additionally, ethanolamine is employed as an organic linker of the 2D layered perovskite, which further improves the moisture stability. This work reveals the strong dependence of the surface conditions of 2D hybrid perovskite crystals on their moisture stability and optoelectronic properties, which are of utmost importance to the design of practical optoelectronic devices based on hybrid perovskite crystals.

A template‐assisted solution‐processed technique is developed to fabricate 3D nanowire‐coated macroporous titania thin films with outstanding optical and electrical properties. Perovskite solar cells based on newly prepared TiO₂ electron‐transporting layer deliver an impressive power conversion efficiency of up to 20.1% owing to enhanced light harvesting and facilitated charge collection.

Abstract

Microscopic design and morphological engineering of the semiconducting metal oxide as electron‐transporting layers (ETLs) is of vital importance for optical enhancement, photonic structuring, and charge collection optimization within optoelectronic devices. Herein, nanowire‐coated, branched macroporous titania (BMT) thin films are reported as a new type of ETL prepared by using silica spheres as a sacrificial template, followed by a sol–gel and subsequent alkaline‐assisted etching process. The BMT films feature 3D hierarchical structures and interconnected networks with tunable pore sizes, branch densities, and film thicknesses. The titania films are employed as ETLs in perovskite solar cells (PSCs), resulting in remarkable power conversion efficiencies (PCEs) of 20.1%; a noticeable 16% increase compared with titania nanowire (TNW) ETL‐based counterparts (PCE = 17.3%). The superior device performance of the BMT‐based PSCs can be attributed to the maximized light harvesting and charge collection capabilities. These beneficial properties are derived from the effective infiltration of the perovskite precursor into the titania macropores, efficient light confinement within the macropore structure, and the textured perovskite capping layer, as well as enhanced charge transport and reduced charge recombination through the BMT architecture. This work demonstrates a simple and effective approach for constructing branched macroporous metal‐oxide photoelectrodes toward high‐performance photovoltaic devices.

A very low‐cost and low‐temperature photovoltaic cell based on dopant‐free contact (transition metal oxide/n‐SiNWs/alkali metal salt) and Si nanowires arrays show a power conversion efficiency of 16.9%. Insights into the interaction between the self‐assembling interface passivation, interface polarities, and the performance of the device is demonstrated.

Abstract

Low‐cost and efficient interfacial layer construction with the required charge selectivity and compatibility is necessary for nanostructured solar cells, and the proper integration of the interfacial layer with the light‐trapping system is required to improve the power conversion efficiency of the cell. Herein, low‐cost Si nanowires‐based solar cells with tunneling heterojunctions are developed by the deposition of MoO _x and spin‐coating of Cs₂CO₃ as the carrier‐selective layers. The power conversion efficiency of 16.9% for a device of 4 cm² in area is achieved by Si nanowires solar cells by the self‐assembly of ultra‐thin SiO _x as the surface tunneling passivation layer. Self‐assembly is realized with an ultraviolet O₃ treatment process at room temperature. Quasi‐steady‐state photoconductance, microwave‐detected photoconductance decay, and constant current–voltage measurements are used to characterize the passivation quality and tunneling transportation properties of the ultra‐thin SiO _x layers. Interfacial charge recombination is suppressed and effective carrier tunneling properties are developed by the growth of ≈1.5 nm thick SiO _x layers on the surfaces of the Si nanowires. This proposed Si nanowires solar cell architecture featuring tunneling heterojunctions achieves high performance and may be suitable for fabricating industrialized Si nanowires‐based photovoltaic devices through a cost‐effective, simple, and low‐temperature process.

All‐small‐molecule organic solar cells employing three nonfullerene acceptors (F‐0Cl, F‐1Cl, and F‐2Cl) are investigated. End group chlorination leads to redshifted absorption, enhanced crystallinity, and high electron mobility. F‐2Cl with highest crystallinity gives the best device performances with power conversion efficiency of 9.89 and 10.76%, respectively, when small molecule DRCN5T and DRTB‐T are used as donors.

Abstract

While a wide variety of nonfullerene acceptors are developed and perform well in combination with polymer donors, only a few nonfullerene acceptors can work well with small molecule donors. Here, all‐small‐molecule solar cells with high performance enabled by a new type of small molecule acceptors (F‐0Cl, F‐1Cl, and F‐2Cl), which contain linear alkyl side chains and end groups substituted with various number of chlorine atoms, are reported. End group chlorination leads to redshifted absorption, enhanced crystallinity, and high electron mobility. These properties make them competitive as electron acceptors for all‐small‐molecule solar devices. When combined with two popular small molecule donors DRTB‐T and DRCN5T, these nonfullerene acceptors offer power conversion efficiencies up to 10.76 and 9.89%, which are among the top efficiencies reported in all‐small‐molecule solar cells and indicate the great potential of all‐small‐molecule solar devices.

Double cation substitution in Cu₂ZnSnS₄ (CZTS) by partially substituting Cu with Ag and Zn with Cd is shown to alter the characteristics of acceptor defects and deep defects responsible for non‐radiative recombination. This synergistic effect of Cd and Ag reflects in power conversion efficiency of 10.1% (10.8% active area) obtained in the (Cu,Ag)₂(Zn,Cd)SnS₄ system.

Abstract

The performance of many emerging compound semiconductors for thin‐film solar cells is considerably lower than the Shockley–Queisser limit, and one of the main reasons for this is the presence of various deleterious defects. A partial or complete substitution of the cations presents a viable strategy to alter the characteristics of the detrimental defects and defect clusters. Particularly, it is hypothesized that double cation substitution could be a feasible strategy to mitigate the negative effects of different types of defects. In this study, the effects of double cation substitution on pure‐sulfide Cu₂ZnSnS₄ (CZTS) by partially substituting Cu with Ag, and Zn with Cd are explored. A 10.1% total‐area power conversion efficiency (10.8% active‐area efficiency) is achieved. The role of Cd, Ag, and Cd + Ag substitution is probed using temperature‐dependent photoluminescence, time‐resolved photoluminescence, current–voltage (IV), and external quantum efficiency (EQE) measurements. It is found that Cd improves the photovoltaic performance by altering the defect characteristics of acceptor states near the valence band, and Ag reduces nonradiative bulk recombination. It is believed that the double cation substitution approach can also be extended to other emerging photovoltaic materials, where defects are the main culprits for low performance.

The better interface formed between the NiO _x /perovskite layers in terms of lower density of traps/defects, as well as more balanced charge carriers in the perovskite layer leading to high recombination yield of carriers are the main reasons for significantly improved device efficiency, photostability of perovskite, and operational stability of perovskite light‐emitting diodes.

Abstract

Metal halide perovskites (MHPs) have emerged as promising materials for light‐emitting diodes owing to their narrow emission spectrum and wide range of color tunability. However, the low exciton binding energy in MHPs leads to a competition between the trap‐mediated nonradiative recombination and the bimolecular radiative recombination. Here, efficient and stable green emissive perovskite light‐emitting diodes (PeLEDs) with an external quantum efficiency of 14.6% are demonstrated through compositional, dimensional, and interfacial modulations of MHPs. The interfacial energetics and optoelectronic properties of the perovskite layer grown on a nickel oxide (NiO _x ) and poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate hole injection interfaces are investigated. The better interface formed between the NiO _x /perovskite layers in terms of lower density of traps/defects, as well as more balanced charge carriers in the perovskite layer leading to high recombination yield of carriers are the main reasons for significantly improved device efficiency, photostability of perovskite, and operational stability of PeLEDs.