Chen Weijie

2D perovskites are of great importance to increase both the efficiency and stability of perovskite interfaces. Motivated by the stronger halogen bond interaction, (5FBzAI)₂PbI₄ used as a capping layer in 3D/2D systems self‐organizes with an in‐plane crystal orientation, inducing a reproducible increase of ≈60 mV in the V _oc, and remarkable operational stability.

Abstract

Despite organic/inorganic lead halide perovskite solar cells becoming one of the most promising next‐generation photovoltaic materials, instability under heat and light soaking remains unsolved. In this work, a highly hydrophobic cation, perfluorobenzylammonium iodide (5FBzAI), is designed and a 2D perovskite with reinforced intermolecular interactions is engineered, providing improved passivation at the interface that reduces charge recombination and enhances cell stability compared with benchmark 2D systems. Motivated by the strong halogen bond interaction, (5FBzAI)₂PbI₄ used as a capping layer aligns in in‐plane crystal orientation, inducing a reproducible increase of ≈60 mV in the V _oc, a twofold improvement compared with its analogous monofluorinated phenylethylammonium iodide (PEAI) recently reported. This endows the system with high power conversion efficiency of 21.65% and extended operational stability after 1100 h of continuous illumination, outlining directions for future work.

Research on flexible mobile energy‐supply devices will promote the development of the Internet of Things. An embedded metal nickel (Ni)‐mesh transparent conductive electrode is used as a flexible substrate for perovskite solar cells (PSCs). These Ni‐mesh‐based PSCs exhibit excellent electric properties and remarkable environmental and mechanical stability.

Abstract

The rapid development of Internet of Things mobile terminals has accelerated the market's demand for portable mobile power supplies and flexible wearable devices. Here, an embedded metal‐mesh transparent conductive electrode (TCE) is prepared on poly(ethylene terephthalate) (PET) using a novel selective electrodeposition process combined with inverted film‐processing methods. This embedded nickel (Ni)‐mesh flexible TCE shows excellent photoelectric performance (sheet resistance of ≈0.2–0.5 Ω sq⁻¹ at high transmittance of ≈85–87%) and mechanical durability. The PET/Ni‐mesh/polymer poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS PH1000) hybrid electrode is used as a transparent electrode for perovskite solar cells (PSCs), which exhibit excellent electric properties and remarkable environmental and mechanical stability. A power conversion efficiency of 17.3% is obtained, which is the highest efficiency for a PSC based on flexible transparent metal electrodes to date. For perovskite crystals that require harsh growth conditions, their mechanical stability and environmental stability on flexible transparent embedded metal substrates are studied and improved. The resulting flexible device retains 76% of the original efficiency after 2000 bending cycles. The results of this work provide a step improvement in flexible PSCs.

In tandem organic photovoltaics, most ultraviolet–visible photons are absorbed by the front sub‐cell, so in the rear sub‐cell, excitons generated on large‐bandgap donors will be reduced significantly. This reduces the conductivity and limits the hole‐transporting property of the rear sub‐cell. An infrared‐absorbing polymer donor is introduced, which provides a second hole‐generation/transporting mechanism to minimize the aforementioned detrimental effects.

Abstract

In tandem organic photovoltaics, the front subcell is based on large‐bandgap materials, whereas the case of the rear subcell is more complicated. The rear subcell is generally composed of a narrow‐bandgap acceptor for infrared absorption but a large‐bandgap donor to realize a high open‐circuit voltage. Unfortunately, most of the ultraviolet–visible part of the photons are absorbed by the front subcell; as a result, in the rear subcell, the number of excitons generated on large‐bandgap donors will be reduced significantly. This reduces the (photo) conductivity and finally limits the hole‐transporting property of the rear subcell. In this work, a simple and effective way is proposed to resolve this critical issue. To ensure sufficient photogenerated holes in the rear subcell, a small amount of an infrared‐absorbing polymer donor as a third component is introduced, which provides a second hole‐generation and transporting mechanism to minimize the aforementioned detrimental effects. Finally, the short‐circuit current density of the two‐terminal tandem organic photovoltaic is significantly enhanced from 10.3 to 11.7 mA cm⁻² (while retaining the open‐circuit voltage and fill factor) to result in an enhanced power conversion efficiency of 15.1%.

Publication date: December 2020

Source: Nano Energy, Volume 78

Author(s): Qing Ma, Zhenrong Jia, Lei Meng, Jinyuan Zhang, Huotian Zhang, Wenchao Huang, Jun Yuan, Feng Gao, Yan Wan, Zhanjun Zhang, Yongfang Li

A novel bifacial passivation strategy which simultaneously suppresses trap states within TiO₂ and perovskite through interaction between functional groups and defects is demonstrated for printable mesoscopic PSCs. The passivation treatment to TiO₂ surface not only reduces the energy barrier between TiO₂ and perovskite for accelerating the charge transfer but also passivates the uncoordinated Pb defects on the perovskite interface.

Surface defects, which mediate nonradiative recombination, are detrimental to both the photovoltaic performance and stability of perovskite solar cells (PSCs). Improving photovoltage and fill factor (FF) in screen‐printed mesoporous PSCs is a major challenge for approaching the power conversion efficiency (PCE) of the planar configured devices. Herein, a novel bifacial passivation strategy which simultaneously suppresses deep trap states within TiO₂ and perovskite through interaction between functional groups and defects is demonstrated for fully printable mesoscopic PSCs. The application of monoethanolamine (MEA) treatment to TiO₂ surface not only reduces the energy barrier between TiO₂ and perovskite for accelerating the charge transfer but also passivates the uncoordinated Pb defects on the perovskite interface. Due to the synergistic effect of charge extraction promotion and trap passivation, the fabricated PSCs deliver a champion PCE of 15.5% with an enhanced V _oc of 0.94 V and FF of 70.4% compared with PSCs without MEA passivation, and the device maintains 97% of its topmost PCE after 240 h under constant simulated solar illumination in air atmosphere. This investigation helps exploit new approaches for defect passivation to further improve both the efficiency and stability of printable mesoscopic PSCs.

A fibril network strategy is demonstrated to fabricate high‐efficiency thick‐film organic solar cells (OSCs). The fibril network morphology provides effective hole transport channel and the incorporation of high crystalline nonfullerene acceptor ensures high electron transport in a thick film. As a result, the OSCs show high efficiencies to ≈12% with wide toleration of active layer thickness.

Industrial printing production of organic solar cells (OSCs) requires high power conversion efficiency (PCE) with wide toleration of active layer thickness. Herein, high‐efficiency thick‐film OSCs are demonstrated using a polymer fibril network strategy (FNS), which involves a donor polymer (PT2) that can self‐assemble into fibril nanostructure, and two nonfullerene acceptors with different crystalline properties. The fibril network can form a high‐speed hole transport channel and the addition of IDIC as a third component in active layers can improve the electron transport. As a result, the OSCs show high PCEs of ≈12% with wide toleration of active layer thickness (from 100 to 500 nm). The results indicate that FNS is a promising approach for the fabrication of highly efficient thick‐film PSCs, which can facilitate the commercialization of OSCs.

An efficient photon downshifting layer is developed based on ultrasonic spray deposition of a platinum(II) complex, and considerable improvements in both the performance and stability of perovskite solar cells are observed. The photon downshifting layer is demonstrated to be applicable to various types of perovskite solar cells, achieving a maximum device performance of 22.0%.

Abstract

Despite a rapid increase in light harvesting efficiencies, organic–inorganic hybrid perovskite solar cells (PSCs) exhibit relatively inefficient photocurrent generation in the UV region and severe degradation when exposed to UV light and humidity. Herein, to enhance UV and humidity stability as well as photocurrent generating efficiency, a water‐repellent platinum(II) complex, Pt‐F, is developed as a luminescent photon downshifting layer (PDL) for PSCs. The Pt‐F PDL is fabricated on the glass substrate of a PSC using ultrasonic spray deposition, resulting in a considerably higher crystallinity and photoluminescence quantum yield (PLQY) than those fabricated by conventional spin‐coating processes (PLQYs of 77% and 19%, respectively). A maximum device performance of 22.0% is achieved through the addition of a PDL coating to a 21.4% efficient PSC owing to the long‐range photon downshifting effect of Pt‐F, as confirmed by the enhanced spectral response of the device in the UV region. Moreover, remarkable improvements in UV and humidity stability are observed in Pt‐F‐coated PSCs. The versatile effects of the Pt‐F‐based PDL, when fabricated by ultrasonic spray deposition, suggest wide ranging applicability that can improve the performance and stability of other optoelectronic devices.

Three homologous small molecule donors with hydrogen, fluorine, and chlorine substitution afford organic solar cells with efficiencies over 10% in combination with a common acceptor. The chlorinated derivative exhibits a more crystalline nanomorphology with relatively pure domains and provides more than 12% efficiency.

Abstract

Compared to conjugated polymers, small‐molecule organic semiconductors present negligible batch‐to‐batch variations, but presently provide comparatively low power conversion efficiencies (PCEs) in small‐molecular organic solar cells (SM‐OSCs), mainly due to suboptimal nanomorphology. Achieving precise control of the nanomorphology remains challenging. Here, two new small‐molecular donors H13 and H14, created by fluorine and chlorine substitution of the original donor molecule H11, are presented that exhibit a similar or higher degree of crystallinity/aggregation and improved open‐circuit voltage with IDIC‐4F as acceptor. Due to kinetic and thermodynamic reasons, H13‐based blend films possess relatively unfavorable molecular packing and morphology. In contrast, annealed H14‐based blends exhibit favorable characteristics, i.e., the highest degree of aggregation with the smallest paracrystalline π–π distortions and a nanomorphology with relatively pure domains, all of which enable generating and collecting charges more efficiently. As a result, blends with H13 give a similar PCE (10.3%) as those made with H11 (10.4%), while annealed H14‐based SM‐OSCs have a significantly higher PCE (12.1%). Presently this represents the highest efficiency for SM‐OSCs using IDIC‐4F as acceptor. The results demonstrate that precise control of phase separation can be achieved by fine‐tuning the molecular structure and film formation conditions, improving PCE and providing guidance for morphology design.

Water is added into the precursor solution to assist crystal growths of quasi‐2D perovskite films featuring ordered phase distribution and favored crystal orientation. A champion efficiency of 18.04% is realized in (BA)₂(MA_0.8FA_0.15Cs_0.05)₄Pb₅I₁₆‐based quasi‐2D perovskite solar cells.

Abstract

Organic–inorganic hybrid quasi‐2D perovskites have shown excellent stability for perovskite solar cells (PSCs), while the poor charge transport in quasi‐2D perovskites significantly undermines their power conversion efficiency (PCE). Here, studies on water‐controlled crystal growth of quasi‐2D perovskites are presented to achieve high‐efficiency solar cells. It is demonstrated that the (BA)₂MA₄Pb₅I₁₆‐based PSCs (n = 5) processed with water‐containing precursors display an increased short‐circuit current density (J _sc) of 19.01 mA cm⁻² and PCE over 15%. The enhanced performance is attributed to synergetic growths of the 3D and 2D phase components aided by the formed hydration (MAI∙H₂O), leading to modulations on the crystal orientation and phase distribution of various n‐value components, which facilitate interphase charge transfer and charge sweepout throughout the device. The water‐assisted crystallization is further applied to triple cation‐based (BA)₂(MA_0.8FA_0.15Cs_0.05)₄Pb₅I₁₆ quasi‐2D perovskites, which generate a remarkable PCE of 18.04%. Despite the presence of water in the precursors, the devices exhibit a satisfactory thermal stability with the PCE degradation <15% under continuous thermal aging at 60 °C for over 500 h.

Electronically active ionenes were realized by integration of naphthalene diimide into a polymer backbone. These conductive polymers have a low degree of crystalline order, show a great processing advantage to remove energy barriers between organic semiconductors and metal electrodes, and afford fullerene‐based, non‐fullerene‐based, as well as ternary organic solar cells with high performance and a maximum efficiency of 16.9 %.

Abstract

Self‐doping ionene polymers were efficiently synthesized by reacting functional naphthalene diimide (NDI) with 1,3‐dibromopropane (NDI‐NI) or trans‐1,4‐dibromo‐2‐butene (NDI‐CI) via quaternization polymerization. These NDI‐based ionene polymers are universal interlayers with random molecular orientation, boosting the efficiencies of fullerene‐based, non‐fullerene‐based, and ternary organic solar cells (OSCs) over a wide range of interlayer thicknesses, with a maximum efficiency of 16.9 %. NDI‐NI showed a higher interfacial dipole (Δ), conductivity, and electron mobility than NDI‐CI, affording solar cells with higher efficiencies. These polymers proved to efficiently lower the work function (WF) of air‐stable metals and optimize the contact between metal electrode and organic semiconductor, highlighting their power to overcome energy barriers of electron injection and extraction processes for efficient organic electronics.

Substitutions of oxygen atoms with sulfur atoms in the ladder‐type heteroheptacene core boost the power conversion efficiency of nonfullerene acceptor from 4.21 % to 15.24 %. This result suggests the importance of key atoms in the conjugated backbone of nonfullerene acceptors, which can significantly affect their energy levels, band gap, charge transport, charge separation, and photovoltaic properties.

Abstract

The design, synthesis, and characterization of two novel nonfullerene acceptors (M8 and M34) based on ladder‐type heteroheptacenes with different heterocycles are reported. Replacing the furan heterocycles with the thiophene heterocycles in the heteroheptacene backbone leads to a hypsochromically shifted absorption band and greatly improved carrier transport for the resulting nonfullerene acceptor (M34) although the π–π‐stacking distances are barely affected. Bulk‐heterojunction polymer solar cells fabricated from M34 and a wide band gap polymer (PM6) as the donor showed a best power conversion efficiency (PCE) of 15.24 % with an open circuit voltage (V_OC) of 0.91 V, much higher than a PCE of 4.21 % and a V_OC of 0.83 V for the counterparts based on M8:PM6. These results highlight the importance of key atoms in the construction of high‐performance nonfullerene acceptors.

A methylammonium chloride (MACl) additive is used to synthesize FA_1–x MA _x PbI₃ films. The best molar fraction of this additive is determined. The MA content in thin films actually used in solar cells is x = 0.06. This amount is thermodynamically the best for the stabilization of this highly efficient perovskite. The perovskite solar cell achieves a stabilized power conversion efficiency as high as 22.06%.

Nowadays, complex chemistry and precursor solution compositions are developed to stabilize hybrid perovskite films and boost the efficiency of perovskite solar cells (PSCs). In this context, determining the actual composition of these layers, especially in organic cations, and understanding the chemistry behind is challenging. Herein, the introduction of methylammonium (MA⁺) in formamidinium lead iodide (FAPbI₃) 3D perovskite is considered to stabilize the α‐phase, whose quantity must be minimized to reduce the material hydrophilicity and its possible destabilization by degassing. The key effects of methylammonium chloride (MACl) additive on the growth of FA_1–x MA _x PbI₃ perovskite layers are studied. Liquid nuclear magnetic resonance (NMR) is used to analyze the photovoltaic layers. NMR peaks and their origin are identified. The MA and FA content in films actually used in PSCs is reliably measured and prepared over a large additive molar concentration ratio. x is quantified at 0.06 ± 0.01 for pure films, which corresponds to the best entropic compound stabilization. It results in PSCs with a stabilized power conversion efficiency as high as 22.06%. These PSCs are shown to be highly stable under solar irradiation and high moisture.

A series of copolymers via a random copolymerization approach are designed and synthesized. The well‐defined fibril interpenetrating morphology with appropriate phase separation in PT2‐based blends can efficiently suppress the unfavorable aggregation, resulting in excellent morphological stability and high efficiency. The work demonstrates the importance of optimization of fibril network morphology in realizing high‐efficiency and ambient‐stable polymer solar cells.

Abstract

Morphological stability is crucially important for the long‐term stability of polymer solar cells (PSCs). Many high‐efficiency PSCs suffer from metastable morphology, resulting in severe device degradation. Here, a series of copolymers is developed by manipulating the content of chlorinated benzodithiophene‐4,8‐dione (T1‐Cl) via a random copolymerization approach. It is found that all the copolymers can self‐assemble into a fibril nanostructure in films. By altering the T1‐Cl content, the polymer crystallinity and fibril width can be effectively controlled. When blended with several nonfullerene acceptors, such as TTPTT‐4F, O‐INIC3, EH‐INIC3, and Y6, the optimized fibril interpenetrating morphology can not only favor charge transport, but also inhibit the unfavorable molecular diffusion and aggregation in active layers, leading to excellent morphological stability. The work demonstrates the importance of optimization of fibril network morphology in realizing high‐efficiency and ambient‐stable PSCs, and also provides new insights into the effect of chemical structure on the fibril network morphology and photovoltaic performance of PSCs.

The M13 bacteriophage functions as an effective perovskite growth template and a passivator in perovskite solar cells. This is owing to its filamentous and uniform dimension, as well as the amino acids on its surface. These effects enhance when the M13 viruses are denatured at high temperature. The efficiency increases from 17.8% to 20.1% upon addition of the denatured viruses.

Abstract

The M13 bacteriophage, a nature‐inspired environmentally friendly biomaterial, is used as a perovskite crystal growth template and a grain boundary passivator in perovskite solar cells. The amino groups and carboxyl groups of amino acids on the M13 bacteriophage surface function as Lewis bases, interacting with the perovskite materials. The M13 bacteriophage‐added perovskite films show a larger grain size and reduced trap‐sites compared with the reference perovskite films. In addition, the existence of the M13 bacteriophage induces light scattering effect, which enhances the light absorption particularly in the long‐wavelength region around 825 nm. Both the passivation effect of the M13 bacteriophage coordinating to the perovskite defect sites and the light scattering effect intensify when the M13 virus‐added perovskite precursor solution is heated at 90 °C prior to the film formation. Heating the solution denatures the M13 bacteriophage by breaking their inter‐ and intra‐molecular bondings. The denatured M13 bacteriophage‐added perovskite solar cells exhibit an efficiency of 20.1% while the reference devices give an efficiency of 17.8%. The great improvement in efficiency comes from all of the three photovoltaic parameters, namely short‐circuit current, open‐circuit voltage, and fill factor, which correspond to the perovskite grain size, trap‐site passivation, and charge transport, respectively.

A multi‐layer front contact system is investigated for efficient perovskite solar cells, which allows for realizing improved light incoupling by reducing the optical losses. The front contact consists of a thin nickel‐oxide (electron‐beam vapor physical deposition‐grown), and a thick pyramidal textured zinc‐oxide (metal‐organic chemical vapor deposition‐grown) layers. Optics and electrical characteristics of solar cells are investigated by 3D electromagnetic simulations.

Abstract

Efficient hole transport layer (HTL) is crucial for realizing efficient perovskite solar cells (PSCs). In this study, nickel‐oxide (NiO_X) thin‐films are investigated as a potential HTL for PSCs. The NiO_X films are prepared by electron‐beam physical vapor deposition at low temperatures. The crystalline properties and the work function are determined by X‐ray diffraction and photoelectric yield spectroscopy. The transmission and the complex refractive index of the films are determined by optical spectroscopy and ellipsometry. Furthermore, PSCs are fabricated and characterized. The short‐circuit current density (J _sc) of the PSC is limited by the optical loss due to the NiOx front contact. The optical losses of the front contact are quantified by optical simulations using finite‐difference time‐domain simulations, and a solar cell structure with improved light incoupling is designed. Furthermore, the electrical characteristics of the solar cell are simulated by finite element method simulations. As a result, it is found that the optical losses can be reduced by 70%, and the light incoupling can be improved so that the J _SC can be increased by up to 12%, allowing for the realization of PSCs with an energy conversion efficiency of 22%. Findings from the numerical simulations are compared with experimentally realized results.

Antisolvent engineering is employed to tune the crystal nucleation and grain growth of perovskite for achieving efficient perovskite solar cells. The engineering of perovskites treated with the green antisolvent MABr‐Eth, suppressing defects‐induced nonradiative recombination in perovskite solar cells, is developed. As expected, the device delivers over 21% power conversion efficiency and a better storage and light‐soaking stability.

Abstract

Organic–inorganic hybrid perovskites have attracted considerable attention due to their superior optoelectronic properties. Traditional one‐step solution‐processed perovskites often suffer from defects‐induced nonradiative recombination, which significantly hinders the improvement of device performance. Herein, treatment with green antisolvents for achieving high‐quality perovskite films is reported. Compared to defects‐filled ones, perovskite films by antisolvent treatment using methylamine bromide (MABr) in ethanol (MABr‐Eth) not only enhances the resultant perovskite crystallinity with large grain size, but also passivates the surface defects. In this case, the engineering of MABr‐Eth‐treated perovskites suppressing defects‐induced nonradiative recombination in perovskite solar cells (PSCs) is demonstrated. As a result, the fabricated inverted planar heterojunction device of ITO/PTAA/Cs_0.15FA_0.85PbI₃/PC₆₁BM/Phen‐NADPO/Ag exhibits the best power conversion efficiency of 21.53%. Furthermore, the corresponding PSCs possess a better storage and light‐soaking stability.

High‐performance semitransparent organic solar cells are achieved through combined design efforts on the formulation of near‐infrared ternary blends and optical control over photonic reflectors, which exhibit excellent features of power generation, they being see‐through, and infrared reflection.

Abstract

Clean energy production and saving play vital impacts on the sustainability of the global community. Herein, high‐performance semitransparent organic solar cells (ST‐OSCs) with excellent features of power generation, being see‐through, and infrared reflection of heat dissipation, with promising perspectives for building‐integrated photovoltaics (BIPVs) are reported. To simultaneously improve average visible transmittance (AVT) and power conversion efficiency (PCE), formally in a trade‐off relationship, of ST‐OSCs, new ternary blends with alloy‐like near‐infrared (NIR) acceptors are employed, which are effective to improve device efficiency while maintaining visible absorption unchanged, resulting in PCEs of 16.8% for opaque devices and 13.1% for semitransparent OSCs (AVT of 22.4% and infrared photon radiation rejection (IRR) of 77%). Further, multifunctional ST‐OSCs are realized via introducing simple, yet effective photonic reflectors, together with optical simulation, leading to not only perfect fitting of the visible transmittance peak (555 nm) to the photopic response of the human eye but also an excellent IRR of 90% (780–2500 nm), along with 23% AVT and over 12% PCE. This is thought to be the best‐performing multifunctional ST‐OSC with promising prospects as BIPVs in terms of power generation, heat dissipation, and being see‐through.

TiO _x N _y films are demonstrated to be an excellent electron‐selective contact for both crystalline silicon and organic solar cells. Remarkable efficiency of 22.3% and 17.02% is achieved for crystalline silicon and organic solar cells, respectively.

Abstract

High‐quality carrier‐selective contacts with suitable electronic properties are a prerequisite for photovoltaic devices with high power conversion efficiency (PCE). In this work, an efficient electron‐selective contact, titanium oxynitride (TiO _x N _y ), is developed for crystalline silicon (c‐Si) and organic photovoltaic devices. Atomic‐layer‐deposited TiO _x N _y is demonstrated to be highly conductive with a proper work function (4.3 eV) and a wide bandgap (3.4 eV). Thin TiO _x N _y films simultaneously provide a moderate surface passivation and enable a low contact resistivity on c‐Si surfaces. By implementation of an optimal TiO _x N _y ‐based contact, a state‐of‐the‐art PCE of 22.3% is achieved for a c‐Si solar cell featuring a full‐area dopant‐free electron‐selective contact. Simultaneously, conductive TiO _x N _y is proven to be an efficient electron‐transport layer for organic photovoltaic (OPV) devices. A remarkably high PCE of 17.02% is achieved for an OPV device with an electron‐transport TiO _x N _y layer, which is superior to conventional ZnO‐based devices with a PCE of 16.10%. Atomic‐layer‐deposited TiO _x N _y ETL on a large area with a high uniformity may help accelerate the commercialization of emerging solar technologies.

A gradient grain‐sized (GGS) CsPbI₃ bilayer is developed to stabilize the α phase via a single‐step film‐deposition process. The perovskite solar cell based on the GGS CsPbI₃ bilayer shows an efficiency of 15.5% and operates stably for 1000 h under ambient conditions.

Abstract

The emerging inorganic CsPbI₃ perovskites are promising wide‐bandgap materials for application in tandem solar cells, but they tend to transit from a black α phase to a yellow δ phase in ambient conditions. Herein, a gradient grain‐sized (GGS) CsPbI₃ bilayer is developed to stabilize the α phase via a single‐step film deposition process. The spontaneously upward migration of (adamantan‐1‐yl)methanammonium (ADMA) based on the hot‐casting technique causes self‐assembly of the hierarchical morphology for the perovskite layers. Due to the strong steric effect of the surficial ADMA cation, a self‐assembly tiny grain‐sized CsPbI₃ layer is in situ formed at the surface site, which exhibits notably enhanced phase stability by its high surface energy. Meanwhile, a large grain‐sized CsPbI₃ layer is obtained at the bottom site with high charge mobility and low trap density of states, which benefits from the regulated growth rates by the interaction between ADMA and perovskites. The perovskite solar cell (PSC) based on the GGS CsPbI₃ bilayer shows an efficiency of 15.5% and operates stably for 1000 h under ambient conditions. This work confirms that redistributing the surface energy of perovskite films is a facile strategy to stabilize metastable PSCs without the cost of efficiency loss.

Electronically active ionenes were realized by integration of naphthalene diimide into a polymer backbone. These conductive polymers have a low degree of crystalline order, show a great processing advantage to remove energy barriers between organic semiconductors and metal electrodes, and afford fullerene‐based, non‐fullerene‐based, as well as ternary organic solar cells with high performance and a maximum efficiency of 16.9 %.

Abstract

Self‐doping ionene polymers were efficiently synthesized by reacting functional naphthalene diimide (NDI) with 1,3‐dibromopropane (NDI‐NI) or trans‐1,4‐dibromo‐2‐butene (NDI‐CI) via quaternization polymerization. These NDI‐based ionene polymers are universal interlayers with random molecular orientation, boosting the efficiencies of fullerene‐based, non‐fullerene‐based, and ternary organic solar cells (OSCs) over a wide range of interlayer thicknesses, with a maximum efficiency of 16.9 %. NDI‐NI showed a higher interfacial dipole (Δ), conductivity, and electron mobility than NDI‐CI, affording solar cells with higher efficiencies. These polymers proved to efficiently lower the work function (WF) of air‐stable metals and optimize the contact between metal electrode and organic semiconductor, highlighting their power to overcome energy barriers of electron injection and extraction processes for efficient organic electronics.

Studies on effect of additives of FAX (X = Cl, Br, and I, FA = formamidinium) and ACl (A = MA, Cs, Rb, and NH₄) in FAPbI₃‐based perovskite solar cells reveal that the FACl additive shows best performance over other additives due to passivating the grain boundary effectively without altering bandgap of pristine perovskite.

Herein, the dependence of photovoltaic performance on the additives of FAX (X = Cl, Br, and I, FA = formamidinium) and ACl [A = methylammonium (MA), Cs, Rb, and NH₄] in FAPbI₃‐based perovskite solar cells (PSCs) is reported. Effect of concentration on photovoltaic parameters is first screened for each additive, from which optimal concentration is determined with respect to the pristine without additive. Power conversion efficiency (PCE) is significantly improved from 16.55% to 22.51% after adding 20 mol% FACl in the perovskite precursor solution, whereas moderate increase in PCE to 20.08% and 19.97% is observed for FABr and FAI, respectively, indicating an important role of chloride. MACl and CsCl improved PCE to 20.81% and 20.59%, respectively, which is, however, inferior to FACl. A significantly increased carrier lifetime by treating FACl is responsible for the best performance. Energy dispersive X‐ray spectroscopy shows that chloride in the additive FACl is not incorporated in grain but placed on the grain boundary, which plays an important role in passivating iodide‐deficient grain boundary. The FACl additive has benefits over other additives because it cannot change the bandgap of FAPbI₃.

An aqueous‐solution‐processed cathode interlayer based on cost‐effective organosilica nanodots (OSiNDs) is demonstrated for organic solar cells (OSCs) with power conversion efficiency over 17% and excellent operational stability. The high photostability of OSiNDs‐based OSCs is attributed to the avoidance of photoinduced shunts and the photocatalytic effect, which are ineluctable shortcomings in inverted OSCs based on ZnO cathode interlayers.

Abstract

The performance and industrial viability of organic photovoltaics are strongly influenced by the functionality and stability of interface layers. Many of the interface materials most commonly used in the lab are limited in their operational stability or their materials cost and are frequently not transferred toward large‐scale production and industrial applications. In this work, an advanced aqueous‐solution‐processed cathode interface layer is demonstrated based on cost‐effective organosilica nanodots (OSiNDs) synthesized via a simple one‐step hydrothermal reaction. Compared to the interface layers optimized for inverted organic solar cells (i‐OSCs), the OSiNDs cathode interlayer shows improved charge carrier extraction and excellent operational stability for various model photoactive systems, achieving a remarkably high power conversion efficiency up to 17.15%. More importantly, the OSiNDs’ interlayer is extremely stable under thermal stress or photoillumination (UV and AM 1.5G) and undergoes no photochemical reaction with the photoactive materials used. As a result, the operational stability of inverted OSCs under continuous 1 sun illumination (AM 1.5G, 100 mW cm⁻²) is significantly improved by replacing the commonly used ZnO interlayer with OSiND‐based interfaces.