吴晓晓

CsBr dual‐interface modification is employed in CsPbIBr₂ perovskite solar cells to facilitate crystallization and passivate surface defects and the synergistic interface modification finally generates the improved power conversion efficiency and stability.

Abstract

The organic‐inorganic hybrid perovskite solar cell has been a rising star in photovoltaics (PV) in the last decade due to its high efficiency and the fastest efficiency‐rise among all known materials in the PV history. The newly developed all‐inorganic perovskite, for its high stability against thermal and light irradiation stresses, is recognized as a promising material for both PV and general optoelectronic applications. Interface and its modification have been proven to play an important role in the solar cell performance. However, all previous research on the all‐inorganic CsPbIBr₂ based solar cells limits their scope to only one surface/interface while ignoring the other. Herein, synergistic effect is discovered when proper amount of CsBr is introduced on both sides of the perovskite active layer. It is found that the TiO₂/perovskite interface modification reduces pinhole and trap‐state densities while modification on perovskite/Spiro‐OMeTAD promotes smoother surface and better crystallinity. The synergistic effect of both modifications leads to increased efficiency to 10.33% with V _OC of 1.24 V, both are among the highest for these types of solar cells. In addition, the optimized device retains 60% of its initial efficiency after 60 h of aging in ambient atmosphere.

A multi-functional interfacial layer composed of a mixture of a poly(oxyethylene tridecyl ether) surfactant and an ethanolamine compound is introduced between a CH₃NH₃PbI₃ perovskite light-harvesting layer and a nickel oxide hole transport layer. Due to the improved film-forming and hole-extracting capabilities, excellent photovoltaic performance is successfully realized together with reduced recombination losses.

Abstract

Recently, hybrid organic–inorganic perovskite solar cells (PVSCs) have attracted significant attention owing to their simple solution processability and high efficiency for the next generation of low-cost solar cell technology. Herein, a multi-functional interfacial layer (IFL) composed of a mixture of poly(oxyethylene tridecyl ether) (PTE) and ethanolamine (EA) is introduced between a CH₃NH₃PbI₃ perovskite light-absorbing layer and a nickel oxide (NiO _x ) hole transport layer to improve the photovoltaic (PV) performance of PVSCs. With the solution-coated IFL of mixed PTE:EA, a highly improved film-forming capability of the perovskite layer is realized together with large-sized grains and fewer film defects. Moreover, the IFL also improved the charge carrier separation and hole-extraction capabilities at the interface between the CH₃NH₃PbI₃ and the NiO _x layers. The results here successfully demonstrate that the CH₃NH₃PbI₃ PVSC with IFL exhibits greatly improved PV performance, in this case a much higher power conversion efficiency (15.1%), greatly exceeding that (12.3%) of a reference device without an IFL. The author's study demonstrates that a multi-functional mixed IFL can be used as a solid foundation for efficient and cost-effective PVSCs, thus providing a platform for the realization of a new generation of highly efficient solution-processable PVSCs.

A spray pyrolysis‐processed nickel oxide (sp‐NiO _x ) thin film is developed as an hole transport layer (HTL) for CsBi₃I₁₀ based inverted (p–i–n) planar perovskite solar cell (PSC). The sp‐NiO _x HTL improves the device stability with excellent optical and electrical properties.

Abstract

Lead (Pb)‐free bismuth (Bi) halide perovskites are promising alternatives to Pb‐based ones for the fabrication of perovskite solar cells (PSCs). However, the energy‐level mismatch at the interface between Bi perovskite (CsBi₃I₁₀;CBI) and the charge carrier transport layer limits the performance of the PSCs. Here, spray pyrolysis processed nickel oxide (sp‐NiO _x ) is reported as a hole transport layer (HTL) for CBI‐based inverted planar PSCs. Influence of inorganic NiO _x HTL is systematically studied on the structural and morphological properties of the CBI perovskite layer growth. The CBI perovskite deposited on top of the sp‐NiO _x exhibits improved crystallinity. The fabricated sp‐NiO _x layer also exhibits favorable optical and electrical properties. The deep valence band (−5.4 eV) of the sp‐NiO _x HTL is able to reduce the energy‐level mismatch up to 0.3 eV at the interface with the CBI layer. The PSCs fabricated with sp‐NiO _x as HTL also exhibits a power conversion efficiency (PCE) of 0.72%, with a short‐circuit current density of 2.89 mA cm⁻². The sp‐NiO _x HTL based device maintains 85% of its initial PCE value even after 100 h of light soaking. This work highlights the importance of having a suitable HTL along with appropriate interface engineering for the Bi halide photovoltaic devices.

The connected bamboo‐leaves‐like structure is formed in poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)‐assisted metal‐phthalocyanine layer, which is used as a hole transporting layer in the inverted perovskite solar cells. The device with PEDOT:PSS‐assisted metal‐phthalocyanine tetrasulfonic acid shows a significant improvement in stability owing to the reduced pH of the hole transport layer compared with the device using pristine PEDOT:PSS.

Abstract

Interface engineering is critical for reducing trap states present in various device interfaces and improving the efficiency of perovskite solar cells (PSCs). This study introduces the blending effect of poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) into metal‐phthalocyanine−tetrasulfonated acid tetrasodium salt (TS‐MPc) used as a hole transport layer (HTL) in organic–inorganic hybrid PSCs. PEDOT:PSS with a low pH induces the self‐assembly and formation of mesh‐like nano‐networks in a TS‐MPc layer, which is confirmed by atomic force microscopy and elemental mapping using energy‐dispersive spectroscopy. Compared with pure TS‐MPc, nano‐networked TS‐MPc with PEDOT:PSS exhibits higher crystallinity by grazing‐incidence wide‐angle X‐ray scattering. The nano‐network formation contributes to ≈30% enhancement in the power conversion efficiency (14.65%) of device with PEDOT:PSS‐assisted TS‐CuPc as HTL, compared with device using conventional PEDOT:PSS (11.02%). In addition, the device with PEDOT:PSS‐assisted TS‐MPc shows a significant improvement in stability owing to the reduced pH of the HTL compared with the device using pristine PEDOT:PSS.

The high‐quality CsPbCl₃ microcrystal films with extremely low defect state density are prepared by antisolvent‐induced crystallization kinetics strategy. Due to the wide bandgap of CsPbCl₃, it is suitable for ultraviolet photodetection. A suitable device structure is designed, and the prepared ultraviolet photodetector based on CsPbCl₃ microcrystalline film has good detection performance for ultraviolet light.

Abstract

CsPbCl₃‐based inorganic perovskite ultraviolet photodetectors (UV‐PDs) have a great promise for the wide application prospects due to the desirably UV‐matched energy band and the excellent intrinsic optoelectronic properties. However, the traditional high‐temperature Bridgman method (near 600 °C) and complexly time‐consuming vapor preparation (several days) of high‐quality CsPbCl₃ crystals have badly restricted its commercial applications to date. Herein, an antisolvent‐induced crystallization kinetics (ACK) strategy is demonstrated for the quick lower‐temperature fabrication (50 °C, tens of minutes) of excellent continuous highly crystalline CsPbCl₃ microcrystal films (MCFs) with low trap density (1.42 × 10¹² cm⁻³). Further, the as‐developed CsPbCl₃ MCF‐based UV‐PDs present a high detectivity of 5.6 × 10¹² Jones, a superior responsivity of 2.11 A W⁻¹, and robust stability. Evidently, this work provides a rapid and simple method to prepare high‐quality perovskite MCFs, greatly promoting the commercial development of perovskite‐based photodetectors.

An in‐situ formed polymeric interlayer enables enhanced photovoltaic performance of the methylammonium‐, cesium‐, and bromide‐free perovskite solar cells with superior photo‐ and thermal‐stability. The polymeric interlayer promotes growth of perovskite crystals with reduced defect density and improves the contact between the perovskite and hole transporting layers to assists in photo‐excited charge extraction.

Abstract

The vast majority of high‐performance perovskite solar cells (PSCs) are based on multi‐cation mixed‐anion compositions incorporating methylammonium (MA) and bromide (Br). Nevertheless, the thermal instability of MA and the tendency of mixed halide compositions to phase segregate limit the long‐term stability of PSCs. However, reports of MA‐free and/or Br‐free compositions are rare in the community since their performance is generally inferior. Here, a strategy is presented to achieve highly efficient and stable PSCs that are altogether cesium (Cs)‐free, MA‐free and Br‐free. An antisolvent quenching process is used to in‐situ deposit a polymeric interlayer to promote the growth of phase‐pure formamidinium lead tri‐iodide perovskite crystals with reduced defect density and to assist in photo‐excited charge extraction. The PSCs developed are among the best‐performing reported for such compositions. Moreover, the PSCs show superior stability under continuous exposure to both illumination and 85 °C heat.

A series of donor–π–acceptor porphyrins coded as CS0, CS1, and CS2 that can effectively passivate the perovskite surface, increase V _OC and FF, reduce the hysteresis effect, enhance power conversion efficiency to be higher than 22%, and improve the device stability have been developed.

Abstract

In recent years, hybrid perovskite solar cells (PSCs) have attracted much attention owing to their low cost, easy fabrication, and high photoelectric conversion efficiency. Nevertheless, solution‐processed perovskite films usually show substantial structural disorders, resulting in ion defects on the surface of lattice and grain boundaries. Herein, a series of D–π–A porphyrins coded as CS0, CS1, and CS2 that can effectively passivate the perovskite surface, increase V _OC and FF, reduce the hysteresis effect, enhance power conversion efficiency to be higher than 22%, and improve the device stability is developed. The results in this study demonstrated that the donor–π–acceptor type porphyrin derivatives are promising passivators that can improve the cell performance of PSCs.

Aided by theoretical calculations, a multifunctional 2,2‐difluoropropanediamide (DFPDA) molecule that bears carbonyl, amino, and fluorine groups is first introduced into the perovskite precursor, serving as a crystal growth mitigator, grain boundaries passivator, and surface protection material. With the help of the combined effects of multifunctional groups in DFPDA, the perovskite cells deliver an efficiency of 22.21% and improved stability.

Abstract

With a certified efficiency as high as 25.2%, perovskite has taken the crown as the highest efficiency thin film solar cell material. Unfortunately, serious instability issues must be resolved before perovskite solar cells (PSCs) are commercialized. Aided by theoretical calculation, an appropriate multifunctional molecule, 2,2‐difluoropropanediamide (DFPDA), is selected to ameliorate all the instability issues. Specifically, the carbonyl groups in DFPDA form chemical bonds with Pb²⁺ and passivate under‐coordinated Pb²⁺ defects. Consequently, the perovskite crystallization rate is reduced and high‐quality films are produced with fewer defects. The amino groups not only bind with iodide to suppress ion migration but also increase the electron density on the carbonyl groups to further enhance their passivation effect. Furthermore, the fluorine groups in DFPDA form both an effective barrier on the perovskite to improve its moisture stability and a bridge between the perovskite and HTL for effective charge transport. In addition, they show an effective doping effect in the HTL to improve its carrier mobility. With the help of the combined effects of these groups in DFPDA, the PSCs with DFPDA additive achieve a champion efficiency of 22.21% and a substantially improved stability against moisture, heat, and light.

The molecular orientation, charge transfer behavior, and dipole formation dynamic of a kind of water/alcohol soluble amino‐functionalized polyelectrolyte (PFN) in organic solar cells are investigated by X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. A large absorption energy and charge transfer between PFN and different substrates are verified for the first time.

Water‐/alcohol‐soluble polyelectrolyte poly[(9, 9‐bis (3′‐(N,N‐dimethylamino) propyl)‐2, 7‐fluorene)‐alt‐2, 7‐(9, 9‐dioctylfluorene)] (PFN) used in organic solar cells (OSCs) reduces the work function of the electrode due to the effect of an interfacial dipole, which is beneficial for the energy‐level alignment between the electrode and the active layer. To date, the studies on the working mechanism of PFN are mainly conducted through topographical and electronic research. Herein, a dynamic insight into the formation mechanisms of the PFN interlayer at the molecular structural level is established. The charge transfer between PFN and the substrates is verified for the first time by X‐ray photoelectron spectroscopy (XPS) and density functional theory (DFT) studies, which results in chemisorption dipoles with their direction aligned with the intrinsic dipole of the PFN molecule, thereby reducing the work function of the substrate. The larger adsorption energy in the substrates of the nitrogen‐containing side chains of PFN is also identified, which induces the preferential orientation of PFN molecule to reduce the work function of the substrate. By incorporating this interlayer, high efficiency in single‐junction OSCs is achieved using commercial materials. The findings are of great significance for understanding and optimizing the polymer dipole interlayers for OSCs.

Perovskite nanocrystals (PCNs) have great application potential in the field of photocatalysis, but their inherent shortcomings are hindering development. The construction of heterostructures is one of the most effective ways to solve these problems. Herein, this article systematically categorizes the effective construction strategies of PCNs heterostructures for perovskites’ urgent issues and gives a future outlook.

Perovskite nanocrystals (PNCs) have recently emerged as a new type of promising photocatalytic semiconductor due to their unique photoelectrochemical properties, including tunable bandgap and crystal structure, entire visible spectral response, and versatile chemical processability. However, under practical circumstance, this type of pure‐phase PNCs photocatalyst demonstrates poor stability, limited light utilization, and high carrier recombination, resulting in low solar power conversion efficiency and inferior catalytic activity. To address these issues, extensive research efforts have been devoted to developing PNCs‐based heterostructures. Thus, a perspective on the development of PNCs‐based heterophotocatalysts is timely. In this Review, the progress of PNCs‐based heterophotocatalysts is presented starting from fundamental properties (i.e., crystal and bandgap structure, photoelectronic properties, etc.) to state‐of‐the‐art applications with a focus on stability improving, dispersion enhancing, and interfacial charge carrier dynamic optimizing. Critical insights are further provided into the existing challenges and prospects for high‐quality PNCs‐based heterostructures in advanced photocatalytic applications.

The results of a comparative investigation of two conformational isomers with different molecular crystallinity, not only provide a comprehensive insight into the photooxidation properties and attenuation mechanisms of organic materials, but also suggest guidelines to rationally select materials for stable organic solar cells.

Despite the striking progress toward improving the efficiencies of organic solar cells (OSCs) resulting from the development of nonfullerene acceptors (NFAs), there is a rising requirement of investigation of the molecular design for achieving photochemically stable NFAs. Herein, applying two isomeric NFA molecules a‐IDTBTRh and l‐IDTBTRh based on angular‐indaceno[2,1‐b:6,5‐b′]dithiophene (a‐IDT) and linear‐IDT (l‐IDT) as the central cores, the effects of molecular conformation, aggregation behavior, and environmental factors on their photooxidation degradation processes are systematically studied. It is found that tuning regioisomeric central cores on the molecular skeleton influences the backbone conformation and conjugation, resulting in the different optoelectronic properties and molecular stacking characteristics. A strong molecular aggregation dependence of the optical losses and degradation mechanics in the annealed neat films is also observed, and it is shown that l‐IDTBTRh is much more photostable than its less‐ordered core derivative, a‐IDTBTRh. Furthermore, the effects of external environmental stresses on photobleaching behaviors of the annealed thin films are studied systematically, highlighting the role of concentrated light in accelerating photooxidation of organic materials. The results not only provide a comprehensive insight into the photooxidation properties and attenuation mechanisms of organic materials, but also suggest guidelines to rationally select materials for stable OSCs.

Sodium diethyldithiocarbamate (NaDEDTC) as processing agent enhances the open‐circuit voltage of methylammonium lead triiodide perovskite solar cells. DEDTC modulates film formation, improves the charge transfer between the hole transporting layer and the perovskite, and reduces nonradiative recombination. However, it is not incorporated in the perovskite or present as a surface ligand.

The incorporation of additives to modulate the properties of metal halide perovskite thin films has become a successful approach in improving the power conversion efficiency of perovskite‐based solar cells. Herein, the beneficial use of sodium diethyldithiocarbamate (NaDEDTC) as processing agent in improving the open‐circuit voltage of methylammonium lead triiodide perovskite solar cells is reported. DEDTC reduces the rate of perovskite crystallization. Absorption and emission spectra show that the optical bandgap of the perovskite films remain essentially unchanged and X‐ray diffraction reveals the formation of preferentially oriented crystallites independent of the use of DEDTC. The use of DEDTC, however, results in a decrease in nonradiative decay as inferred from a two order of magnitude increase in electroluminescence efficiency, explaining the increased open‐circuit voltage. Fourier‐transform infrared spectroscopy, nuclear magnetic resonance, and X‐ray photoelectron spectroscopy show that the DEDTC ligand is not present after the film processing. Therefore, DEDTC modulates film formation but is not incorporated in the perovskite or present as a surface ligand. Sodium ions, on the contrary, are incorporated in the perovskite layer.

The carbon‐based hole‐transporting material (HTM)‐free CsPbBr₃ perovskite solar cell (PSC) achieves a maximized power conversion efficiency (PCE) of 9.82% with an excellent thermal and moisture stability through perovskite film management and multiple‐ionic defect passivation by the introduction of a tetra‐bisphenol A (TBBPA) additive.

High‐quality perovskite films with low imperfections, high hole mobility, and matching energy levels play a crucial role in enhancing performance of perovskite solar cells (PSCs) without hole‐transporting materials (HTMs). Herein, it is demonstrated that the incorporation of a stable tetra‐bisphenol A (TBBPA) with diphenyl ring, polybromides, and hydroxyl groups additive into a perovskite film can simultaneously manipulate the crystal growth and passivate the defects through coordination interaction between the functional group (OH, Br) and the unsaturated halogen and metal ions (Br⁻, Cs⁺, and Pb²⁺), resulting in a reduced grain boundary as well as imperfection and increased hole mobility of the CsPbBr₃ perovskite film. In addition, the valence band of a perovskite film with TBBPA additive is shifted upward to approach the work function of the carbon electrode, thereby improving the energy level alignment. Consequently, a significantly boosted charge extraction and reduced charge recombination of the carbon‐based HTM‐free CsPbBr₃ PSCs is obtained after incorporating the TBBPA additive, yielding a maximum power conversion efficiency of up to 9.82% of the optimized device. Furthermore, the champion PSC without encapsulation displays a remarkable thermal and moisture stability after being kept in ambient air for 720 h at 85 °C and 85% relative humidity, respectively.

Ultrathin MoO _x ‐doped carbon nanotube‐embedded polyimide films are fabricated as transparent substrates for foldable perovskite solar cells. The carbon nanotube‐polyimide matrix prevents the peeling of carbon electrode from the substrate and facilitates anaerobic thermal p‐doping using MoO _x . The transparent conductors exhibit state‐of‐the‐art mechanical stability because of their ultra‐thinness and record‐high efficiency and outstanding durability.

Abstract

Recently, foldable electronics technology has become the focus of both academic and industrial research. The foldable device technology is distinct from flexible technology, as foldable devices have to withstand severe mechanical stresses such as those caused by an extremely small bending radius of 0.5 mm. To realize foldable devices, transparent conductors must exhibit outstanding mechanical resilience, for which they must be micrometer‐thin, and the conducting material must be embedded into a substrate. Here, single‐walled carbon nanotubes (CNTs)–polyimide (PI) composite film with a thickness of 7 µm is synthesized and used as a foldable transparent conductor in perovskite solar cells (PSCs). During the high‐temperature curing of the CNTs‐embedded PI conductor, the CNTs are stably and strongly p‐doped using MoO _x , resulting in enhanced conductivity and hole transportability. The ultrathin foldable transparent conductor exhibits a sheet resistance of 82 Ω sq.⁻¹ and transmittance of 80% at 700 nm, with a maximum‐power‐point‐tracking‐output of 15.2% when made into a foldable solar cell. The foldable solar cells can withstand more than 10 000 folding cycles with a folding radius of 0.5 mm. Such mechanically resilient PSCs are unprecedented; further, they exhibit the best performance among the carbon‐nanotube‐transparent‐electrode‐based flexible solar cells.

The triple-cation mixed-halide perovskite (FA_xMA_yCs_1-x-y)Pb(I_zBr_1-z)₃ (FAMACs) is the best composition for thin-film solar cells. Unfortunately, there is no effective method to prepare large single crystals (SCs) for more advanced applications. Here, we report an effective additive strategy to grow 2-inch-sized high-quality FAMACs SCs. It is found that the judiciously selected reductant [formic acid (FAH)] effectively minimizes iodide oxidation and cation deprotonation responsible for phase segregation. Consequently, the FAMACs SC shows more than fivefold enhancement in carrier lifetimes, high charge mobility, long carrier diffusion distance, as well as superior uniformity and long-term stability, making it possible for us to design high-performance self-powered integrated circuit photodetector. The device exhibits large responsivity, high photoconductive gain, excellent detectivity, and fast response speed; all values are among the highest reported to date for planar-type single-crystalline perovskite photodetectors. Furthermore, an integrated imaging system is fabricated on the basis of 12 x 12 pixelated matrixes of the single-crystal photodetectors.

Exceptional water‐stability has been confirmed in DMASnBr₃ and exploited in photocatalysis to enhance the hydrogen photogeneration of graphitic carbon nitride.

Abstract

Water‐stable metal halide perovskites could foster tremendous progresses in several research fields where their superior optical properties can make differences. In this work we report clear evidence of water stability in a lead‐free metal halide perovskite, namely DMASnBr₃, obtained by means of diffraction, optical and X‐ray photoelectron spectroscopy. Such unprecedented water‐stability has been applied to promote photocatalysis in aqueous medium, in particular by devising a novel composite material by coupling DMASnBr₃ to g‐C₃N₄, taking advantage from the combination of their optimal photophysical properties. The prepared composites provide an impressive hydrogen evolution rate >1700 μmol g⁻¹ h⁻¹ generated by the synergistic activity of the two composite costituents. DFT calculations provide insight into this enhancement deriving it from the favorable alignment of interfacial energy levels of DMASnBr₃ and g‐C₃N₄. The demonstration of an efficient photocatalytic activity for a composite based on lead‐free metal halide perovskite in water paves the way to a new class of light‐driven catalysts working in aqueous environments.

The discussion focuses on how the crystallographic properties and the structure of the Ruddlesen–Popper perovskite impact the efficiency of the solar cells. The strategies for film processing and material design in past studies and the potential research directions in the future are discussed.

Abstract

Metal halide Ruddlesen–Popper perovskite solar cells (RPPSCs) have attracted a great deal of attention in the research community due to their excellent stability over the 3D counterparts. In 2014, the first RPPSC was reported achieving a power conversion efficiency (PCE) of about 4.7%. To date, this type of solar cells reach a PCE exceeding 18% on lab scale. In this essay, distil strategies to further improve the PCE of RPPSCs are discussed. First, the unique physical properties of RPP are discussed to highlight the importance of film processing and material design, and then the factors that are limiting RPPSCs with special focus on the crystallographic and charge transport properties are addressed. Finally, the opportunities for RPPSCs are discussed, and opinions are provided regarding how to further improve the performance of these devices and on strategies which may advance the technology toward its industrial exploitation.

It is shown that the reversible redox (photo)chemistry between Pb²⁺ and I^– represents the main cause of light‐induced phase segregation in mixed‐halide and/or mixed‐cation perovskite formulations. Furthermore, these findings shed new insights on the underlying mechanisms of multiple other phenomena related to light‐ or electric field‐induced degradation of various lead halide perovskites.

Abstract

Tunability of optoelectronic properties of lead halide perovskites achieved through halide mixing can potentially enable their multiple applications, for example, in tandem solar cells and light‐emitting diodes. However, mixed halide perovskites are unstable under illumination due to their segregation to Br‐rich and I‐rich phases, which negatively affects the performance and the operational stability of devices. Research efforts over the past years provided a substantial understanding of the factors influencing light‐induced halide phase segregation. While several mechanisms have been proposed, none of them could account for all available experimental data; and hence the origin of the effect is still under active debate. Herein, the photodegradation of CsPbI₂Br and Cs_1.2PbI₂Br_1.2 is thoroughly investigated using a set of complementary techniques. In situ atomic force microscopy provides a visualization of the real‐time halide phase segregation dynamics demonstrating that iodoplumbate is selectively expelled from the mixed halide perovskite grains and nucleates as a separate I‐rich phase at the grain boundaries. A mechanism based on the reversible Pb²⁺/Pb⁰ and I⁻/I₃ ⁻ redox (photo)chemistry is proposed, which explains the experimental findings and other previously reported results. Furthermore, it sheds new insights on the underlying mechanisms of multiple phenomena related to light‐ or electric field‐induced degradation of various lead halide perovskites.

The effect of Pd cross‐coupling catalyst traces on the physical processes in a non‐fullerene bulk‐heterojunction solar cell is investigated. The drop of the solar cell performance upon addition of systematically added amounts of tetrakis(triphenylphosphine)palladium(0) is explained by alteration of the morphology, charge carrier generation, recombination, and charge extraction.

Abstract

The effect of the cross‐coupling catalyst tetrakis(triphenylphosphine)palladium(0) (Pd(PPh₃)₄) on the performance of a model organic bulk‐heterojunction solar cell composed of a blend of 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}) (PTB7‐Th) donor and 3,9‐bis(2‐methylene‐((3‐(1,1‐dicyanomethylene)‐6,7‐difluoro)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d′]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene (IOTIC‐4F) non‐fullerene acceptor is investigated. The effect of intentional addition of different amounts of Pd(PPh₃)₄ on morphology, free charge carrier generation, non‐geminate bulk trap‐ and surface trap‐assisted recombination as well as bimolecular recombination and charge extraction is quantified. This work shows that free charge carrier generation is affected significantly, while the impact of Pd(PPh₃)₄ on non‐geminate recombination processes is limited because the catalyst does not facilitate efficient trap‐assisted recombination. The studied system shows substantial robustness towards the addition of Pd(PPh₃)₄ in small amounts.