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A cyclometalated Pt(IV) compound, Pt(dfpypy)2(Me)Cl (1), with blue phosphorescence was prepared using 2′,6′-difluoro-2,3′-bipyridine (dfpypy) as a C^N chelate ligand. Compound 1 exhibits distorted octahedral geometries around the platinum ion and has strong intermolecular interactions via interatomic contacts (H···N/F/Cl) involving hydrogen bond interactions based on Hirshfeld surface analysis. This compound shows bright blue phosphorescence emissions with λmax = 427 and 455 nm and a high photoluminescence quantum efficiency (ΦPL = 0.60). Furthermore, a good blue colour purity with Commission Internationale de L'Eclairage (1931) coordinates ( x, y) of (0.14, 0.17) was observed in the thin film, which was close to pure blue. TD-DFT calculations revealed that the electronic transition can be attributed to a combination of intraligand charge transfer (πbpy–π*bpy) and ligand-to-ligand charge transfer [pz(Cl)–π*(dfpypy)] with a small contribution from metal-to-ligand charge transfer (Ptd−π*bpy). Owing to the introduction of the electronegative C^N chelate dfpypy, the emission of compound 1 was blueshifted by 20 nm compared with its analog [Pt(ppy)2(Me)Cl] ( λmax = 447), where ppy is 2-phenylpyridine.

In the crystal of the title compound, which shows blue–green emission, the mol­ecules are connected via C—H⋯Cl/F, halogen⋯π and weak π–π stacking inter­actions., The title compound, [Pt(C21H12F2N3O)Cl], crystallizes with two crystallographically independent mol­ecules (A and B) in the asymmetric unit, which adopt similar conformations. The PtII atoms in both mol­ecules adopt distorted square-planar geometries, coordinated by one C and two N atoms from the tridentate 2′,6′-di­fluoro-6-[3-(pyridin-2-yl­oxy)phen­yl]-2,3′-bi­pyridine ligand and a chloride anion: the C and Cl atoms are trans. In the crystal, C—H⋯Cl/F hydrogen bonds, F⋯π and weak π–π stacking inter­actions between adjacent A and B mol­ecules and between pairs of inversion-related B mol­ecules lead to the formation of a two-dimensional supra­molecular network lying parallel to the ab plane. The sheets are stacked along the c-axis direction and linked by F⋯π and weak π–π stacking inter­actions between pairs of inversion-related A mol­ecules, forming a three-dimensional supra­molecular network. The photoluminescence quantum efficiency of the title compound in the blue–green region of the visible region (λmax = 517 and 544 nm) is estimated to be ∼0.2–0.3, indicating that the title compound could be a suitable candidate as the emitting material in organic light-emitting diode (OLED) applications.

Hybrid lead halide perovskites will potentially lead the future energy scenario if highly efficient cells have long-term stability. Here we combine state-of-the art mixed-cation formulations containing formamidinium (FA) and methylammonium (MA), with optimal guanidinium (Gua)/Cs ratios, enabling the realization of cells providing stability at their maximum efficiency.

The AgI atom in the title compound, which exhibits strong blue emission, adopts a highly distorted trigonal–planar geometry coordinated by two pyridine N atoms of two crystallographically independent 2′,6′-di­fluoro-2,3′-bi­pyridine ligands and one O atom of the tri­fluoro­metane­sulfonate anion., In the title compound, [Ag(CF3SO3)(C10H6F2N2)2], the AgI centre adopts a highly distorted trigonal–planar coordination environment resulting from its coordination by one O atom of the tri­fluoro­methane­sulfonate anion and the pyridine N atoms of two crystallographically independent 2′,6′-di­fluoro-2,3′-bi­pyridine ligands, which display very similar conformations to one another. Pairwise Ag⋯O–SO2CF3 − [Ag⋯O = 2.8314 (14) Å] inter­actions and inter­molecular C—H⋯O inter­actions between inversion-related units lead to the formation of an eight-membered cyclic dimer in which the silver atoms are separated by 6.2152 (3) Å. In the crystal, the dimers are linked through C—H⋯O hydrogen bonds, halogen⋯π and weak π–π stacking inter­actions, resulting in the formation of a three-dimensional supra­molecular network. The title compound exhibits a strong and broad emission band from 400 nm to 550 nm in solution and its photoluminescence quantum efficiency is estimated to be ca 0.2, indicating that the title compound could have applications as an emitting material in organic light-emitting diodes (OLEDs).

Methylammonium (MA) is one of the main obstacles that hold back the commercialization of perovskite solar cells (PSCs). Formamidinium (FA)-based perovskite is a promising photovoltaic material due to its higher thermal stability and smaller bandgap. However, despite the introduction of Cs+ in FAPbI3, the photoactive α-phase FAPbI3 can quickly transform into a non-perovskite hexagonal phase δ-FAPbI3, which limits its use in perovskite solar cells. In this work, we show that the dispersion of 2D (PEA)2PbI4 nanosheets into a Cs0.1FA0.9PbI3 thin film successfully prevents the transformation of the α-phase Cs0.1FA0.9PbI3 to the δ-phase. Because of the 2D (PEA)2PbI4 nanosheets, a higher quality perovskite thin-film was obtained with a longer carrier lifetime, lower trap state density, and enhanced stability. The resulting device achieves a high power conversion efficiency of 20.44%, which is one of the highest for MA-free perovskites and retains 82% of its initial efficiency after 800 h of aging study.

Surface passivation is a critical factor for improving the photovoltaic performance of perovskite solar cells. However, more robust principle investigations are required to build effective passivation strategies enabling high-performance perovskite solar cells. Here, it is demonstrated that a non-reactive organic polymer induces band-bending at the perovskite surface through a passivation effect, furthermore suppressing Pb0 formation at the perovskite surface. Consequently, the photovoltaic performance and stability of the perovskite solar cells can be improved. The key findings show that the polymer passivation layer can control the Fermi-level at the perovskite surface, which changes the band structure at the perovskite surface and affects carrier dynamics by suppressing non-radiative pathways. Moreover, the organic polymer can prevent degradation of the perovskite surface. By using the passivating layer, the open circuit voltage improves from 1.046 to 1.100 V, the photoconversion efficiency exceeds 21%, and the stability of the perovskite solar cells is substantially improved. The organic polymer poly(bisphenol A anhydride-co-1,3-phenylenediamine) (PEIm) was used to control the perovskite band structure, and this passivation mechanism is revealed here.

Engineering two-/three-dimensional (2D/3D) perovskite solar cells is nowadays a popular strategy for efficient and stable devices. However, the exact function of the 2D/3D interface in controlling the long-term device behavior is still obscure. Here, we reveal a dynamical structural mutation of the 2D/3D interface: the small cations in the 3D cage move towards the 2D layer, which acts as an ion scavenger. If structurally stable, the 2D layer physically blocks the ion movement at the interface boosting the device stability. Otherwise, the 2D layer embeds them, dynamically self-transforming into a quasi-2D structure. The judicious choice of the 2D constituent is decisive in controlling the 2D/3D kinetics and improving the device lifetime, opening a new avenue for perovskite interface design.

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., 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.

We report the effect of applied pulse width on charge accumulation in triple cation perovskite solar cells (PSCs) during the Electric Field Induced Second Harmonic Generation (EFISHG) measurements. The PSCs were prepared in the n-i-p structure using the layer-by-layer deposition technique. The triple cation perovskite precursor containing FAPbI3, MAPbBr3, and CsPbI3 was used to make the perovskite layer on the FTO/c-TiO2/mTiO2 substrates. Spiro OMeTAD was used as a hole transport material over the perovskite active layer, followed by the deposition of Au electrodes. The average power conversion efficiency (PCE) of the fabricated PSCs was 19.17 ± 0.02%. The electric field in the PSCs was selectively probed by the fundamental laser beam wavelength of 960 nm during the EFISHG measurements. Two different pulse widths (100 µs and 50 ms) of the applied potential were used in this study, with consideration of electrode charging and interface charging of PSCs. It has been observed that the pulse width of the applied electric field has a significant effect on the charge accumulation in the PSCs. Using the transient EFISHG measurements, it has also been found that the charging & discharging processes reversibly happen. However, the charging & discharging processes are influenced by remained charges at the interface in PSCs in the investigated triple cations PSCs. The EFISHG results can be well explained by using the Maxwell–Wagner model.

An unsymmetrical zinc phthalocyanine with one carboxyl and three tert-butyl groups (TT1) and a symmetrical zinc phthalocyanine with four tert-butyl groups (TT0) are employed as hole-transporting materials (HTMs) in mixed-ion perovskite [HC(NH2)2]0.1(CH3NH3)0.9PbI3 solar cells. The optical and electrochemical data of TT1 and TT0 exhibit appropriate energy levels for efficient interfacial charge transfer with the perovskite. The perovskite solar cells with TT1 show 16 ± 1 mA/cm2 photocurrent and 0.95 ± 0.07 V open circuit voltage resulting in 13.0 ± 0.7% power conversion efficiency at 1 sun. Under the same conditions, the symmetric phthalocyanine TT0 shows 20.2 mA/cm2 photocurrent and 1.05 V open circuit voltage resulting in 14% power conversion efficiency.

In this work, for the first time, reactive radical-cation species present in hole-transporting materials were shown to react with tert-butylpyridine additive, routinely used in hole transporting layer composition. As a result, new pyridinated products were isolated and characterized by NMR and MS analysis. Additionally, their optical and photophysical properties (i.e., solid-state ionization potentials (Ip), cyclic voltammetry (CV), UV/vis characteristics, and conductivities) were determined. Formation of the pyridinated products was confirmed in the aged perovskite solar cells by means of mass spectrometry, and shown to have negative influence on the overall device performance. We believe that these findings will help improve the stability of perovskite devices by either molecular engineering of hole-transporting materials or utilization of less-reactive or sterically hindered pyridine derivatives.

Methods for effective synthesis for the four possible isomeric 3,9-diphenylullazine carboxaldehydes and reactive halogen intermediates are described. Ullazine donor-acceptor (D-A) dyes were studied using UV/Vis, photoluminescence (PL) spectroscopy and cyclic voltammetry. X-ray single crystal diffraction analysis independently confirmed the structures of two key intermediates. A D-A dye based on ullazine with dihexylmalonate acceptor was tested as a dopant-free hole-transporting material (HTM) in a perovskite solar cell, exhibiting promising power conversion efficiency (PCE) reaching 13.07 %.

With a power conversion efficiency (PCE) exceeding 22 %, perovskite solar cells (PSCs) have thrilled photovoltaic research. However, the interface behavior is still not understood and is a hot topic of research: different processes occur over a hierarchy of timescales, from femtoseconds to seconds, which makes perovskite interface physics intriguing. Herein, through femtosecond transient absorption spectroscopy with spectral coverage extending into the crucial IR region, the ultrafast interface-specific processes at standard and newly molecularly engineered perovskite interfaces in state-of-the-art PSCs are interrogated. Ultrafast interfacial charge injection occurs with a time constant of 100 fs, resulting in hot transfer from energetic charges and setting the timescale for the first step involved in the complex charge-transfer process. This is also true for 20 % efficient devices measured under real operation, for which the femtosecond injection is followed by a slower picosecond component. These findings provide compelling evidence for the femtosecond interfacial charge-injection step and demonstrate a robust method for the straightforward identification of interfacial non-equilibrium processes on the ultrafast timescale. Fil: Grancini, Giulia. Ecole Polytechnique Federale de Lausanne; Suiza Fil: Viola, Daniele. Politecnico di Milano; Italia Fil: Lee, Yonghui. Ecole Polytechnique Federale de Lausanne; Suiza Fil: Saliba, Michael. Ecole Polytechnique Federale de Lausanne; Suiza Fil: Paek, Sanghyun. Ecole Polytechnique Federale de Lausanne; Suiza Fil: Cho, Kyung Taek. Ecole Polytechnique Federale de Lausanne; Suiza Fil: Orlandi, Simonetta. Consiglio Nazionale delle Ricerche; Italia Fil: Cavazzini, Marco. Consiglio Nazionale delle Ricerche; Italia Fil: Fungo, Fernando Gabriel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Hossain, Mohammad I.. Qatar Environment And Energy Research Institute; Qatar Fil: Belaidi, Abdelhak. Qatar Environment And Energy Research Institute; Qatar Fil: Tabet, Nouar. Qatar Environment And Energy Research Institute; Qatar Fil: Pozzi, Gianluca. Consiglio Nazionale delle Ricerche; Italia Fil: Cerullo, Giulio. Politecnico di Milano; Italia Fil: Nazeeruddin, Mohammad Khaja. Ecole Polytechnique Federale de Lausanne; Suiza

A simple carbazole-based conjugated enamine V950 was synthesized, fully characterized and incorporated into a perovskite solar cell, which displayed high power conversion efficiency close to 18%. The investigated hole transporting material was synthesized via an extremely simple route (one step, no expensive catalysts, no column chromatography or sublimation purification) from commercially available and relatively inexpensive starting reagents, resulting in more than one order of magnitude lower cost of the final product compared to the commercial 2,2′,7,7′-tetrakis(N,N-di-p-methoxy-phenylamine)-9-9′-spirobifluorene (spiro-OMeTAD). This material promises to be a viable p-type organic charge conductor to be employed in the scale-up and manufacturing of perovskite solar modules.

Perovskite solar cells have set a new milestone in terms of efficiencies in the thin film photovoltaics category. Long-term stability of perovskite solar cells is of paramount importance but remains a challenging task. The lack of perovskite solar cells stability in real-time operating conditions erodes and impedes commercialization. Further improvements are essential with a view to delivering longer-lasting photovoltaic (PV) performances. An ideal path in this direction will be to identify novel dopants for boosting the conductivity and hole mobility of hole transport materials (HTMs), and by so doing the usage of hygroscopic and deliquescent additive materials can be avoided. Pyridine-based ionic liquids represent a well-known class of ultra-hydrophobic materials, which are suitable for their application in opto-electrical devices. The present work demonstrates the employment of ionic liquids into a dissymmetric fluorene-dithiophene, FDT (2’,7’ -bis(bis(4-methoxyphenyl)amino) spiro[cyclopenta[2,1-b:3,4-b’]dithiophene-4,9’-fluorene]) based HTM to understand the doping mechanisms. N-heterocyclic hydrophobic ionic liquid, 1-butyl-3-methylpyidinium bis(trifluoromethylsulfonyl)imide (BMPyTFSI) as p-type dopant for FDT was found to increase the conductivity of FDT, to higher geometrical capacitance, to facilitate homogeneous film formation, and to enhance device stability. Our findings open up a broad range of hole-transport materials to control the degradation of the underlying water-sensitive active layer by substituting hygroscopic element.

Surface passivation of the perovskite photo absorber is a key factor to improve the photovoltaic performance. So far robust passivation strategies have not yet been revealed. Here, we demonstrate a successful passivation strategy which controls the Fermi-level of the perovskite surface by improving the surface states. Such Fermi-level control caused band-bending between the surface and bulk of the perovskite, which enhanced the hole-extraction from the absorber bulk to the HTM side. As an added benefit, the inorganic passivation layer improved the device light stability. By depositing a thick protection layer on the complete device, a remarkable waterproofing effect was obtained. As a result, an enhancement ofVOCand the conversion efficiency from 20.5% to 22.1% was achieved. We revealed these passivation mechanisms and used perhydropoly(silazane) (PHPS) derived silica to control the perovskite surface states.

Through judicious molecular engineering, novel dopant-free star-shaped D-pi-A type hole transporting materials coded KR355, KR321, and KR353 were systematically designed, synthesized and characterized. KR321 has been revealed to form a particular face-on organization on perovskite films favoring vertical charge carrier transport and for the first time, we show that this particular molecular stacking feature resulted in a power conversion efficiency over 19% in combination with mixed-perovskite (FAPbI(3))(0.85)(MAPbBr)(0.15). The obtained 19% efficiency using a pristine hole transporting layer without any chemical additives or doping is the highest, establishing that the molecular engineering of a planar donor core, p-spacer and periphery acceptor leads to high mobility, and the design provides useful insight into the synthesis of next-generation HTMs for perovskite solar cells and optoelectronic applications.

Interfacial engineering of the meso-TiO2 surface through a modified sequential deposition procedure involving a novel PbI2–HMPA complex pretreatment is conducted as a reproducible method for preparing MAPbI3 based perovskite solar cells providing the highest efficiencies yet reported with the polymer HTM layer. Grazing-incidence X-ray diffraction depth profiling confirms the formation of a perovskite film with a PbI2-rich region close to the electron transport layer (ETL) due to the strong interaction of HMPA with PbI2, which successfully retarded the dissolution of the PbI2 phase when depositing the perovskite layer on top. These results are further confirmed by energy-dispersive X-ray spectroscopy performed in a scanning transmission electron microscope, which reveals that the I/Pb ratio in samples treated with the complex is indeed reduced in the vicinity of the ETL contact when compared to samples without the treatment. The engineered interface leads to an average power conversion efficiency of 19.2% ...

Correction for ‘Cation optimization for burn-in loss-free perovskite solar devices’ by Sanghyun Paek et al., J. Mater. Chem. A, 2021, 9, 5374–5380, DOI: 10.1039/D1TA00472G.

We investigate the effect of temperature and light soaking on the stability and charge carrier behavior in triple cation 3-Dimensional (3D) and 2-Dimensional (2D)/3-Dimensional perovskite solar cells (PSCs) using electric field induced second harmonic generation (EFISHG) and impedance spectroscopy (IS) techniques. To prepare the 2D/3D perovskite structures, a layer-by-layer deposition method was employed. Spiro-OMeTAD based hole transport layer was deposited on the top of the perovskite layer using a spin coating procedure. The average power conversion efficiency (PCE) of the fresh fabricated cells was 18%. The electric fields in the PSCs were selectively probed by the EFISHG measurements, using the fundamental laser beam wavelength of 960 nm. The results show that the EFISHG technique could be potentially used to identify the degradation mechanism in the PSCs. Also, the IS technique was performed to investigate the electrical parameters affected under light and heat soaking environment. The 2D/3D hybrid PSCs show relatively good stability and better efficiency as compared to 3D PSCs. This work is supported by Qatar University Internal Grant No. QUCG-CAM-2018\19-1 . Scopus

Herein, the optoelectronic properties of interfaceengineered perovskite 2D|3Dheterojunction structure solar cells are reported. The reciprocity theorem is applied to determine the maximum opencircuit voltage (Voc) the device can deliver under solar illumination. A Voc of 1.295V is found, analyzing the measured external quantum efficiency and assuming only radiative recombination. For comparison, the experimental opencircuit voltage found for the studied 2D|3D heterojunctions is 1.15V. The contribution of nonradiative recombination is explored by measuring the electroluminescence quantum yield. A quantum yield of 0.4% is found at current densities equivalent to 1sun illumination. This translates into a Voc loss of 140mV, which is in very good agreement with the experimental findings. In addition, the fundamental correlation between luminescence intensity and the chemical potential predicted by the generalized Planck law is confirmed for the photoluminescence measured at different light intensities when the device is operated under opencircuit conditions and for the electroluminescence when operated under a forward bias. The investigations in this study suggest that further efficiency improvements can be achieved by reducing the nonradiative recombination in the studied solar cell. At the same time, a highperformance near IR light emitting diode can be realized. (VLID)4843823 Version of record

The search for new classes of hole transporting materials (HTMs) is a very important task on the way towards commercialization of perovskite solar cells (PSCs). In this work, the synthesis and performance in PSCs of new enamine-based HTMs are presented. The synthesis scheme is very short, consisting of only one step, starting from commercially available aromatic amines. Moreover, the reaction does not require metal catalysts and is based on condensation chemistry with water as a by-product. It was shown that PSCs with such materials reach high power conversion efficiencies (PCE), with the highest PCE of 19% achieved for the V1021-based device. This work establishes enamines as a very promising class of materials for application in PSCs.

Dimethoxydiphenylamine-substituted dispiro-oxepine derivative 2,2',7,7'-tetrakis-(N,N'-di-4-methoxyphenylamine)dispiro-[fluorene-9,4'-dithieno(3,2-c:2',3'-e]oxepine-6',9 ''-fluorene] (DDOF) has been designed and synthesized using a facile synthetic route. The novel hole transporting material (HTM) was fully characterized and tested in perovskite solar cells exhibiting a remarkable power conversion efficiency of 19.4%. More importantly, compared with spiro-OMe-TAD-based devices, DDOF shows significantly improved stability. The comparatively comprehensive solid structure study is attempted to disclose the common features of good performance HTMs. These achievements clearly demonstrated that the highly hindered DDOF can be an effective HTM for the fabrication of efficient perovskite solar cells and further enlightened the rule of new HTM's design.

A new unsymmetrical low bandgap push–pull squaraine chromophore bis-DMFA-Th-SQ-Th-DCA denoted as JK216D was synthesized and its optical and electrochemical properties (both theoretical and experimental) were investigated. This small molecule having a strong electron withdrawing moiety exhibits a broader absorption band in thin film. The JK216D exhibited suitable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital energy levels, compatible with that of PC71BM, for efficient photoinduced electron transfer. The bulk heterojunction solar cell fabricated with JK216D:PC71BM (optimized weight ratio of 1:2 and processed with CB) exhibited a PCE of 3.60% (Jsc = 9.97 mA cm−2, Voc = 0.86 V and FF = 0.42). The PCE has been further improved up to 5.25% (Jsc = 11.86 mA cm−2, Voc = 0.82 V and FF = 0.54), when the optimized JK216D:PC71BM (1:2) active layer was processed with the addition of 3 v% 1,8-diiodoctane (DIO) into the CB solution.

High efficiency small molecules were synthesized and characterized in solution-processed organic solar cells. These were star-shaped comprising of fused triphenylamine donating core, hexyl cyano acetate or methylene malononitrile accepting edges, and alkyl-substituted therthiophene bridge unit, exhibiting a noteworthy power conversion efficiency of 4.18% in solar cell device from bulk-heterojunction films with PC71BM.

Well-organized (CH3NH3)PbI3 perovskite films fabricated from various solution-processing conditions were characterized and used in hybrid solar cells with PC71BM planar heterojuncion films, exhibiting a high power-conversion efficiency of 12.2% with the better photocurrent and fill factor compared to those with PC61BM due to a better spectral response in the visible region and a better planar junction with the Ag electrode than the PC61BM.

Two symmetrical star-shaped hole transporting materials (HTMs), i.e. FA-MeOPh and TPA-MeOPh with a fused triphenylamine or triphenylamine core and diphenylethenyl side arms were synthesized. FA-MeOPh showed a strong molar absorption coefficient and a red-shifted absorption compared with TPA-MeOPh because of its planar configuration. The power conversion efficiency (PCE) of the perovskite solar cells based on FA-MeOPh and TPA-MeOPh is about 11.86% and 10.79%, in which the efficiency of former is comparable to that (12.75%) of spiro-OMeTAD based cell. The high photocurrent (18.39 mA cm(-2)) of FA-MeOPh based solar cell relative to TPA-MeOPh based one may be attributable to the enhanced absorption in the near-IR region for mp-TiO2/CH3NH3PbI3/HTM based cell. The high mobility and low series resistance of mp-TiO2/CH3NH3PbI3/FA-MeOPh based cell led to the high fill factor (0.698) of FA-MeOPh based solar cell relative to TPA-MeOPh based one (0.627). In addition, the FA-MeOPh based cell showed a relative stability under light soaking for 250 h. The high efficiency, relative stability, synthetically simple and inexpensive materials as the HTMs hold promise to replace the expensive spiro-OMeTAD.

High-performance organic semiconductors based on an electron-rich alkylsilylethynyl benzodithiophene (TIPSBDT) core were newly synthesized and characterized for use in solution-processed small-molecule organic solar cells. The rigid and extended π-conjugation of the TIPSBDT motifs facilitates intramolecular charge transfer and intermolecular π–π packing interactions of semiconducting small molecules in the BHJ film enhanced by processing additives and induces deep HOMO levels producing high open-circuit voltage of ∼1.0 V, exhibiting notable power conversion efficiency of 5.84% from a bulk-heterojunction film with PC61BM.

Two symmetrical planar star-shaped organic small molecules, i.e., DMM-TPA[DTS(FBTTh3)3] (1) and TPA[DTS(FBTTh3)3] (2), with fused TPA and TPA core donors, respectively, and three branched DTS(FBTTh3) units were synthesized and characterized. These small molecules were used donor materials along with a PC71BM acceptor for solution-processed bulk heterojunction solar cells. The power conversion efficiency (PCE) of the solar cells based on 1 and 2 is about 2.87% and 2.51%, respectively, when the active layers were processed from a CB solvent. The higher PCE of the solar cell based on 1 may be attributed to its low bandgap and broad absorption profile as compared to 2. The PCE of the solution-processed SMBHJ solar cells was improved up to 5.16% and 4.70% for 1 and 2, respectively, when the active layers were processed with 4 v% DIO as an additive in the CB solvent. The enhancement in the PCE was mainly due to the increase in Jsc and FF, which is attributed to the balanced charge transport between the electron and hole transport and reduction in the bimolecular recombination, leading to an increase in the PCE.

The synthesis and characterization of unprecedented push–pull organic semiconductors, TPA-Th-DTSi-[HxTh] 2 -HCA ( 1 ), TPA-Th-DTSi-[HxTh] 2 -MMN ( 2 ), bisDMFA-Th-DTSi-[HxTh] 2 -HCA ( 3 ), and bisDMFA-Th-DTSi-[HxTh] 2 -MMN ( 4 )—possessing a π-conjugated thiophene bridge incorporating electron-rich dithienosiole (DTSi) moieties—are described, along with an investigation of their photovoltaic performances in solution-processed SMOSCs. Results showed that the greater intensities of π – π * transitions from the electron-rich Th-DTSi-[HxTh] 2 bridge to [HxTh] 2 -MMN (or [HxTh] 2 -HCA) acceptors provide superior photocurrent efficiencies from absorbed photons compared to those via ICT transition in SMOSCs fabricated with these new materials coupled with PC 71 BM BHJ films. The most efficient SMOSCs fabricated based on this π -conjugation bridge-containing electron-rich DTSi motif exhibited a moderate PCE of 2.34% from skeleton comprising of bisDMFA donor and MMN acceptor.

We meticulously designed organic antenna for the ruthenium phthalocyanine. A significant enhance-ment of photocurrent in JK-107 is attributed to a Forster energy transfer and intramolecular electro...

Perovskite solar cells (PSCs) have experienced an outstanding advance in power conversion efficiency (PCE) by optimizing the perovskite layer morphology, composition, interfaces, and charge collection efficiency. To enhance PCE, here we developed a new method i.e., engineering a compositional gradient thinly at the rear interface between the perovskite and the hole transporting materials. We demonstrate that charge collection is improved and charge recombination is reduced by formation of an engineered passivating layer, which leads to a striking enhancement in open-circuit voltage (VOC). The passivation effect induced by constructing an additional FAPbBr3−xIx layer on top of the primary (FAPbI3)0.85(MAPbBr3)0.15 film was proven to function as an electron blocking layer within the perovskite film, resulting in a final PCE of 21.3%. Our results shed light on the importance of the interfacial engineering on the rear surface of perovskite layers and describe an innovative approach that will further boost the PSC efficiency.

The molecular structure of the hole transporting material (HTM) play an important role in hole extraction in a perovskite solar cells. It has a significant influence on the molecular planarity, energy level, and charge transport properties. Understanding the relationship between the chemical structure of the HTM's and perovskite solar cells (PSCs) performance is crucial for the continued development of the efficient organic charge transporting materials. Using molecular engineering approach we have constructed a series of the hole transporting materials with strategically placed aliphatic substituents to investigate the relationship between the chemical structure of the HTMs and the photovoltaic performance. PSCs employing the investigated HTMs demonstrate power conversion efficiency values in the range of 9% to 16.8% highlighting the importance of the optimal molecular structure. An inappropriately placed side group could compromise the device performance. Due to the ease of synthesis and moieties employed in its construction, it offers a wide range of possible structural modifications. This class of molecules has a great potential for structural optimization in order to realize simple and efficient small molecule based HTMs for perovskite solar cells application.

Interfacial engineering of the meso-TiO

The symmetrical planar star-shaped organic semiconductor DMM-TPA-[DTS(BTTh(3))](3) with fused TPA core donor and three branch motifs, DTS(BTTh(3)), exhibited efficient p-type semiconducting performance in solution-processed SMOSCs and OFETs compared to the tilted star-shaped TPA-[DTS(BTTh(3))](3); a noteworthy PCE value of 4.16% was observed, with a hole mobility and on/off ratio of 7.6 × 10(-3) cm(2) V(-1) s(-1) and 5 × 10(6), respectively.