Facilitate Hole Transfer Research Articles

A hole-selective hybrid TiO2 layer for stable and low-cost photoanodes in solar water oxidation

The use of conductive and corrosion-resistant protective layers represents a key strategy for improving the durability of light absorber materials in photoelectrochemical water splitting. For high performance photoanodes such as Si, GaAs, and GaP, amorphous TiO2 protective overlayers, deposited by atomic layer deposition, are conductive for holes via a defect band in the TiO2. However, when coated on simply prepared, low-cost photoanodes such as metal oxides, no charge transfer is observed through amorphous TiO2. Here, we report a hybrid polyethyleneimine/TiO2 layer that facilitates hole transfer from model oxides BiVO4 and Fe2O3, enabling access to a broader scope of available materials for practical water oxidation. A thin polyethyleneimine layer between the light absorber and the hybrid polyethyleneimine/TiO2 acts as a hole-selective interface, improving the optoelectronic properties of the photoanode devices. These polyethyleneimine/TiO2 modified photoanodes exhibit high photostability for solar water oxidation over 400 h.

Sublimation and Recrystallization of CsPbBr3 Constructing a Perovskite-Carbon Interface to Facilitate Hole Transfer in Printable All-Inorganic Perovskite Solar Cells.

All-inorganic perovskite solar cells (APSCs) are a promising photovoltaic technology due to their unique physical and optical properties. For printable all-inorganic perovskite solar cells, the key factors limiting their photoelectric conversion performance are the crystallization of perovskite and the hole collection capability at the perovskite-carbon interface. In this study, leveraging the high-temperature tolerance of CsPbBr3 perovskite, the sublimation and recrystallization processes were controlled, significantly improving the crystalline quality of the perovskite and suppressing the generation of the nonphotovoltaic CsPb2Br5 phase. Furthermore, a continuous distribution of high-quality CsPbBr3 crystals was achieved at the interface between the carbon electrode and the zirconium oxide layer, ensuring efficient collection of photogenerated holes. The photoelectric conversion efficiency of the printable mesoscopic all-inorganic perovskite solar cell was increased from 5.04 to 8.34% (with a record value of 10.04%) and achieved an ultrahigh open-circuit voltage of 1.54 V due to the significant improvement in the crystal quality of CsPbBr3. This study proposes a novel strategy to enhance the photovoltaic conversion performance of carbon-based all-inorganic perovskite solar cells by suppressing the presence of nonphotovoltaic phases.

Construction of Reverse Type-II InP/ZnxCd1-xS Core/Shell Quantum Dots with Low Interface Strain to Enhance Photocatalytic Hydrogen Evolution.

The InP-based quantum dots (QDs) have attracted much attention in the field of photocatalytic H2 evolution. However, a shell should be used for InP-based photocatalytic systems to passivate the numerous surface defects. Different from the traditional InP-based core/shell QDs with Type-I or Type-II band alignment, herein, the "reverse Type-II" core/shell QDs in which both the conduction and valence bands of shell materials are more negative than those of core materials have been well-designed by regulating the ratio of Cd/Zn of the alloyed ZnxCd1-xS shell. The reverse Type-II band alignment would realize the spatial separation of photogenerated carriers. More importantly, the photogenerated holes tend to rest on the shell in the reverse Type-II QDs, which facilitate hole transfer to the surface, the rate-determining step for solar H2 evolution using QDs. Therefore, the obtained InP/Zn0.25Cd0.75S core/shell QDs exhibit superior photocatalytic activity and stability under visible light irradiation. The rate of solar H2 evolution reaches 376.19 μmol h-1 mg-1 at the initial 46 h, with a turnover number of ∼2,157,000 per QD within 70 h irradiation.

In situ photodeposition of Cu and Ni(OH)2 dual cocatalyst: Synergistic effect on enhancing g-C3N4 photocatalytic H2 evolution

The hydrogen generated through photocatalytic technology is crucial for environmental resources and energy supply. The key to solving photocatalytic efficiency is the migration and compounding of photogenerated carriers. In this paper, Cu is chosen as an electron co-catalyst with good metallic properties to replace the expensive metal. Meanwhile, Ni(OH)2 unites with g-C3N4 to facilitate hole transfer as a hole co-catalyst. The data shows that the g-C3N4 photocatalyst using Cu and Ni(OH)2 as modified co-catalyst has the maximum hydrogen evolution efficiency (2037.3 μmol·g−1·h−1). Due to the Ni(OH)2 and Cu nanoparticles combined with g-C3N4 and their synergistic effect, the hydrogen evolution activity of the dual-loaded photocatalyst is higher than the sum of that of the single-loaded Cu-C3N4 (303.6 μmol·g−1·h−1) and Ni(OH)2-C3N4 (447.3 μmol·g−1·h−1). The photoluminescence spectra (PL) showed that Cu-Ni(OH)2-C3N4 possessed the lowest carrier recombination rate and the fastest carrier transfer rate, consistent with the hydrogen evolution performance results. Data from electrochemical workstations show that composite samples owned a lower electrochemical impedance. The above experiments indicate that the double-loaded synergistic catalytic g-C3N4 possesses a more vital photocatalytic driving force, which has implications for studying energy-catalytic conversion.

Self‐Assembled Monolayers of Bi‐Functionalized Porphyrins: A Novel Class of Hole‐Layer‐Coordinating Perovskites and Indium Tin Oxide in Inverted Solar Cells

AbstractSelf‐assembled monolayers (SAMs) offer the advantage of facile interfacial modification, leading to significant improvements in device performance. In this study, we report the design and synthesis of a new series of carboxylic acid‐functionalized porphyrin derivatives, namely AC‐1, AC‐3, and AC‐5, and present, for the first time, a strategy to exploit the large π‐moiety of porphyrins as a backbone for interfacing the indium tin oxide (ITO) electrode and perovskite active layer in an inverted perovskite solar cell (PSC) configuration. The electron‐rich nature of porphyrins facilitates hole transfer and the formation of SAMs, resulting in a dense surface that minimizes defects. Comprehensive spectroscopic and dynamic studies demonstrate that the double‐anchored AC‐3 and AC‐5 enhance SAMs on ITO, passivate the perovskite layer, and function as conduits to facilitate hole transfer, thus significantly boosting the performance of PSCs. The champion inverted PSC employing AC‐5 SAM achieves an impressive solar efficiency of 23.19 % with a high fill factor of 84.05 %. This work presents a novel molecular engineering strategy for functionalizing SAMs to tune the energy levels, molecular dipoles, packing orientations to achieve stable and efficient solar performance. Importantly, our comprehensive investigation has unraveled the associated mechanisms, offering valuable insights for future advancements in PSCs.

Self-Assembled Monolayers of Bi-Functionalized Porphyrins: A Novel Class of Hole-Layer-Coordinating Perovskites and Indium Tin Oxide in Inverted Solar Cells.

Self-assembled monolayers (SAMs) offer the advantage of facile interfacial modification, leading to significant improvements in device performance. In this study, we report the design and synthesis of a new series of carboxylic acid-functionalized porphyrin derivatives, namely AC-1, AC-3, and AC-5, and present, for the first time, a strategy to exploit the large π-moiety of porphyrins as a backbone for interfacing the indium tin oxide (ITO) electrode and perovskite active layer in an inverted perovskite solar cell (PSC) configuration. The electron-rich nature of porphyrins facilitates hole transfer and the formation of SAMs, resulting in a dense surface that minimizes defects. Comprehensive spectroscopic and dynamic studies demonstrate that the double-anchored AC-3 and AC-5 enhance SAMs on ITO, passivate the perovskite layer, and function as conduits to facilitate hole transfer, thus significantly boosting the performance of PSCs. The champion inverted PSC employing AC-5 SAM achieves an impressive solar efficiency of 23.19% with a high fill factor of 84.05%. This work presents a novel molecular engineering strategy for functionalizing SAMs to tune the energy levels, molecular dipoles, packing orientations to achieve stable and efficient solar performance. Importantly, our comprehensive investigation has unraveled the associated mechanisms, offering valuable insights for future advancements in PSCs.

Strengthened Surface Modification for High-Performance Inorganic Perovskite Solar Cells with 21.3% Efficiency.

Metal halide inorganic perovskites show excellent thermal stability compared to organic-inorganic perovskites. However, the performance of inorganic perovskite solar cells (PSCs) is far from theoretical values, together with unsatisfactory stability, mainly due to the poor interfacial properties. In this work, a facial but effective method is reported to realize high-performance inorganic PSCs by post-modifying the perovskite surface with 2-thiophene ethylamine (TEA). It is found that amine group from TEA can favorably interact with the undercoordinated Pb2+ via Lewis acid-based coordination, while thiophene ring with electron-rich sulfur assists such interaction by functioning as an electron donor. The synergetic interaction allows TEA to passivate perovskite film defects more efficiently, as compared to phenethylamine (PEA) with less electron-donating ability. Moreover, perovskite valence band is slightly upward shift to match with hole transport material and facilitate hole transfer. These combinations result in a reduced non-radiative charge recombination and improved charge carrier lifetime. Consequently, PSCs with TEA modification shows a drastic improvement of VOC by 54mV, yielding a champion PCE of 21.3%, much higher than the control PSCs (19.3%), along with improved ambient stability. This work demonstrates that surface modifier with an electron-rich moiety is critical for achieving efficient and stable inorganic PSCs.

Improved photovoltaic performance and robustness of all-polymer solar cells enabled by a polyfullerene guest acceptor

Fullerene acceptors typically possess excellent electron-transporting properties and can work as guest components in ternary organic solar cells to enhance the charge extraction and efficiencies. However, conventional fullerene small molecules typically suffer from undesirable segregation and dimerization, thus limiting their applications in organic solar cells. Herein we report the use of a poly(fullerene-alt-xylene) acceptor (PFBO-C12) as guest component enables a significant efficiency increase from 16.9% for binary cells to 18.0% for ternary all-polymer solar cells. Ultrafast optic and optoelectronic studies unveil that PFBO-C12 can facilitate hole transfer and suppress charge recombination. Morphological investigations show that the ternary blends maintain a favorable morphology with high crystallinity and smaller domain size. Meanwhile, the introduction of PFBO-C12 reduces voltage loss and enables all-polymer solar cells with excellent light stability and mechanical durability in flexible devices. This work demonstrates that introducing polyfullerenes as guest components is an effective approach to achieving highly efficient ternary all-polymer solar cells with good stability and mechanical robustness.

Photogenerated charge separation at BiVO4 photoanodes enhanced by a Ag-modified porphyrin polymer skeleton.

Bismuth vanadate (BiVO4) has been considered a promising photoactive material in photoelectrochemical (PEC) water-splitting systems. However, the performance of BiVO4-based photoanodes is currently unsatisfactory, indicating the need for new architectural designs to improve their efficiency. In this paper, a porphyrin-phosphazene polymer (THPP-HCCP) was synthesized with a sizeable conjugated structure, and Ag particles were deposited on its surface as an organic-inorganic composite interface improvement layer. The deposition of the composite polymer film on BiVO4 resulted in a significant increase in photocurrent density, reaching up to 2.2 mA cm-2 (1.23 V vs. RHE), almost three times higher than pristine BiVO4, which benefits from the synergistic effect of Ag nanoparticles and porphyrin-phosphazene. Furthermore, photophysical and intensity-modulated photocurrent analysis demonstrated that the Ag-THPP-HCCP heterostructures could broaden the light-absorbing range and facilitate hole transfer to the semiconductor surface, resulting in an improved water oxidation process. The dynamic charge transport behavior of Ag-THPP-HCCP/BiVO4 was investigated using scanning photoelectrochemical microscopy, which showed that the rate constant (Keff) exhibits an almost 4-fold increase compared to pristine BiVO4, indicating a significant improvement in the transport of photogenerated holes. This experiment presents a novel strategy for designing high-efficiency polymer-based photoanodes.

Fast, Multi-Bit, and Vis-Infrared Broadband Nonvolatile Optoelectronic Memory with MoS2 /2D-Perovskite Van der Waals Heterojunction.

Nonvolatile optoelectronic memory (NVOM) integrating the functions of optical sensing and long-term memory can efficiently process and store a large amount of visual scene information, which has become the core requirement of multiple intelligence scenarios. However, realizing NVOM with vis-infrared broadband response is still challenging. Herein, the room temperature vis-infrared broadband NVOM based on few-layer MoS2 /2D Ruddlesden-Popper perovskite (2D-RPP) van der Waals heterojunction is realized. It is found that the 2D-RPP converts the initial n-type MoS2 into p-type and facilitates hole transfer between them. Furthermore, the 2D-RPP rich in interband states serves as an effective electron trapping layer as well as broadband photoresponsive layer. As a result, the dielectric-free MoS2 /2D-RPP heterojunction enables the charge to transfer quickly under external field, which enables a large memory window (104V), fast write speed of 20 µs, and optical programmable characteristics from visible light (405nm) to telecommunication wavelengths (i.e., 1550nm) at room temperature. Trapezoidal optical programming can produce up to 100 recognizable states (>6 bits), with operating energy as low as 5.1 pJ per optical program. These results provide a route to realize fast, low power, multi-bit optoelectronic memory from visible to the infrared wavelength.

Exploring the Polarization Photocatalysis of ZnIn2S4 Material toward Hydrogen Evolution by Integrating Cascade Electric Fields with Hole Transfer Vehicle

AbstractSluggish charge kinetics in photocatalysts and slow hole transfer in oxidation half‐reaction severely limit the photocatalytic activity of hydrogen evolution. ZnIn2S4 with an asymmetrical layered structure of [S–In]–[S–In–S]–[Zn–S] unit cell is a promising material offering asymmetrical crystal polarization to overcome the limitation; however, the polarization‐induced internal electric field by this material remains largely unexplored. Herein, the polarization‐induced internal electric field of ZnIn2S4 by engineering the polarity intensity in microscopic units is demonstrated for the first time. Specifically, ultrathin ZnIn2S4 nanosheets are employed to establish a Ni12P5/ZnIn2S4‐O (NP/ZIS‐O) system with powerful bulk and interface cascade electric field by the oxygen doping and ohmic junction. Enabled by such a design, the photogenerated electrons can rapidly migrate to NP active sites, suppressing the photogenerated electron‐hole pair recombination on ZIS‐O. To further overcome the inefficient hole transfer in oxidation half‐reaction, the preferential dehydrogenation of the α‐CH bond in benzyl alcohol is utilized as a vehicle to facilitate hole transfer. As a result, a remarkably enhanced H2 generation of 15.79 mmol g–1 h–1 is achieved on NP/ZIS‐O, which is 8.16‐fold higher than that of pristine ZnIn2S4. Meanwhile, as a value‐added oxidation product, benzaldehyde can be produced at the rate of 17.63 mmol g–1 h–1. This work presents a collaborative strategy for engineering charge behavior in photocatalysts with polarization features, and provides insights into materials design toward photocatalytic hydrogen production and organic synthesis from the angle of charge kinetics.

Facilitate hole transport with thin 2D perovskite capping layer to passivate interface defects of 3D perovskite solar cells using PEABr

Hybrid 2D/3D-perovskites are attracting more interest in the area of organometal halide perovskite solar cells (PSCs) because of their high efficiency and extended environmental stability. The 3D portion in 2D/3D perovskites, serves as an active material with exceptional optoelectronic characteristics (for example excellent light absorption and an extended carrier lifetime), while its 2D counterpart protects against environmental conditions (water and oxygen) and increase the stability of the whole structure. In this study, a hetero-structure 2D/3D is constructed via spin-coating a phenyl-ethyl ammonium bromide (PEABr) solution upon over of (FA0.6MA0.4)PbI3 3D perovskite films. As compared to their 3D analogs, the PSC devices based on optimized 2D/3D hetero-structures display substantial improvements in photovoltaic efficiency due to the passivation of cationic and halide vacancies on the surface of 3D perovskite for better energy level alignments, longer carrier lifetimes, and fewer defects, which facilitate hole transfer and transport to the hole transport layer and reduce interface recombination centers. The extremely-thin film of 2D perovskite on the top of 3D perovskite boots the stability and reduces the crystal imperfection of 3D perovskite. Furthermore, the PEABr-treated perovskite device has a PCE of 20.57% as compared with the control device, which has a PCE of 17.01%.

Standalone photoconversion of CO2 using Ti and TiOx-sandwiched heterojunction photocatalyst of CuO and CuFeO2 films

Artificial photoconversion of carbon dioxide to value-added chemicals remains a challenge. In this work, we synthesize heterojunction copper oxide and copper iron oxide (CuO/CuFeO2; CFO) films on transparent conducting substrates with metallic Ti layers, and deposit disordered TiOx particles on the CFO films. The Ti/CFO/TiOx samples convert CO2 into formate with ∼100% selectivity and drive O2 evolution under simulated sunlight in the absence of any electrical and chemical biases, achieving the overall solar-to-chemical energy conversion efficiency of ∼5%. The primary roles of the Ti underlayer are to create a robust contact between CFO and substrates and facilitate hole transfer. The TiOx (with unsaturated Ti atoms) delocalizes the electron density of the CFO and enhances electron transfer to the adsorbed CO2. Density functional theory calculations reveal that Ti/CFO/TiOx is the most suitable among the bare and modified CFO samples for efficient CO2 adsorption, formiloxyl intermediate formation, and formate desorption.

High‐Performance All‐Polymer Solar Cells with a Pseudo‐Bilayer Configuration Enabled by a Stepwise Optimization Strategy

AbstractIn this work, an efficiency of 15.17% in the PBDB‐T/PYT all‐PSCs fabricated by a layer‐by‐layer (LbL) deposition technique is achieved by synergistically controlling additive dosages, which is not only higher than that (14.06%) of the corresponding bulk heterojunction (BHJ) device, but also the top efficient for all‐PSCs. Through the studies of physical dynamics and morphological characteristics, it is found that the LbL film can effectively improve optical and electronic properties, ensure exciton separation, charge generation and extraction, reduce trap‐assisted recombination, and facilitate hole transfer in LbL blends, thus achieving higher performance compared to its BHJ counterpart. Notably, the synergistic regulation of additive dosages in donor and acceptor solutions is also confirmed in the other three photovoltaic systems. Of particular note is that over 15% device performance is also achieved in the PBDB‐T/PYT LbL all‐PSCs fabricated via a blade‐coating technique, further demonstrating the great significance of this synergistic additive‐doping strategy for the printing fabrication of organic photovoltaics.

An interesting possibility of forming special hole stepping stones with high-stacking aromatic rings in proteins: three-π five-electron and four-π seven-electron resonance bindings.

Long-range hole transfer of proteins plays an important role in many biological processes of living organisms. Therefore, it is highly useful to examine the possible hole stepping stones, which can facilitate hole transfer in proteins. However, the structures of stepping stones are diverse because of the complexity of the protein structures. In the present work, we proposed a series of special stepping stones, which are instantaneously formed by three and four packing aromatic side chains of amino acids to capture a hole, corresponding to three-π five-electron (π:π∴π↔π∴π:π) and four-π seven-electron (π:π∴π:π↔π:π:π∴π) resonance bindings with appropriate binding energies. The aromatic amino acids include histidine (His), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp). The formations of these special stepping stones can effectively reduce the local ionization potential of the high π-stacking region to efficiently capture the migration hole. The quick formations and separations of them promote the efficient hole transfer in proteins. More interestingly, we revealed that a hole cannot delocalize over infinite aromatic rings along the high π–π packing structure at the same time and the micro-surroundings of proteins can modulate the formations of π:π∴π↔π∴π:π and π:π∴π:π↔π:π:π∴π bindings. These results may contribute a new avenue to better understand the potential hole transfer pathway in proteins.

The critical role of furfural alcohol in photocatalytic H2O2 production on TiO2

Isopropanol is frequently employed as the electron donor to facilitate hole transfer and promote photocatalytic H2O2 production. However, the role of alcohols can be more complicated due to the interaction with TiO2. According to a comparison of aliphatic, aromatic and aromatic heterocyclic alcohols on photocatalytic H2O2 production on TiO2, furfural alcohol (FFA) displays superior capability to others. The presence of alcohols with aromatic structures can significantly accelerate formation and suppress decomposition of H2O2. Moreover, furfural alcohol tends to form more stable complexes on TiO2 surface, which can negatively shift the flat band position, induce visible light activity, and boost two-electron reduction of oxygen. The altered electron transfer pathway for H2O2 production was indicated by the Koutecky-Levich plots, the less pH dependence, and the signals of peroxide species in Raman spectra. This study brings insights for modulating the interfacial oxygen reduction and designing highly efficient and selective H2O2 production photocatalytic systems.

Giant enhancement in photoresponse via engineering of photo-induced charge (electron and hole) transfer in linear and non-linear devices

Zinc oxide (ZnO) has been widely explored for UV detection despite its high exciton binding energy that can inhibit its photoresponse due to high probability of recombination. Here, we describe an approach that suppresses recombination and enhances the photoresponse via engineering of photo-induced charge transfer (PCT) in a linear MSM device Ag/ZnO/Ag and a non-linear p-Si/ZnO junction device. ZnO film when coated with carbon nanotubes (CNTs)/ nitrogen-doped CNTs (NCNTs) facilitates electron transfer and when coated with Poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) facilitates hole transfer, which inhibits recombination, increasing its photocurrent between 275–400 nm. This is one of the interesting approaches to enhance the photoresponse of a material. The extent of PCT depends on the amount of CNTs/NCNTs and PEDOT:PSS. Photocurrent was found to increase by ∼362-fold and ∼607-fold for 365 nm wavelength when NCNTs and NCNTs along with PEDOT:PSS were used as the recombination inhibitor on ZnO thin film, respectively. The responsivity was found to be 153 mA/W and 10.5 A/W, respectively for the coated Ag/ZnO/Ag linear and p-Si/ZnO non-linear device configurations, under 365 nm illumination. The enhancement is ∼15-fold for the non-linear devices. Overall, this work paves the way for an elegant and inexpensive means to hugely enhance photoresponse via engineering the photo-induced charge transfer in linear and non-linear devices. Furthermore, in addition to the photocurrent, the dark current and hence, the conductivity can be engineered via the approach discussed here.

Susceptible Surface Sulfide Regulates Catalytic Activity of CdSe Quantum Dots for Hydrogen Photogeneration.

Semiconducting quantum dots (QDs) have recently triggered a huge interest in constructing efficient hydrogen production systems. It is well established that a large fraction of surface atoms of QDs need ligands to stabilize and avoid them from aggregating. However, the influence of the surface property of QDs on photocatalysis is rather elusive. Here, the surface regulation of CdSe QDs is investigated by surface sulfide ions (S2- ) for photocatalytic hydrogen evolution. Structural and spectroscopic study shows that with gradual addition of S2- , S2- first grows into the lattice and later works as ligands on the surface of CdSe QDs. In-depth transient spectroscopy reveals that the initial lattice S2- accelerates electron transfer from QDs to cocatalyst, and the following ligand S2- mainly facilitates hole transfer from QDs to the sacrificial agent. As a result, a turnover frequency (TOF) of 7950 h-1 can be achieved by the S2- modified CdSe QDs, fourfold higher than that of original mercaptopropionic acid (MPA) capped CdSe QDs. Clearly, the simple surface S2- modification of QDs greatly increases the photocatalytic efficiency, which provides subtle methods to design new QD material for advanced photocatalysis.

Enhanced Solar Water Splitting by Swift Charge Separation in Au/FeOOH Sandwiched Single-Crystalline Fe2 O3 Nanoflake Photoelectrodes.

In this work, single crystalline α-Fe2 O3 nanoflakes (NFs) are formed in a highly dense array by Au seeding of a Fe substrate by a thermal oxidation technique. The NFs are conformally decorated with a thin FeOOH cocatalyst layer. Photoelectrochemical (PEC) measurements show that this photoanode, incorporating α-Fe2 O3 /FeOOH NFs rooted on the Au/Fe structure, exhibits significantly enhanced PEC water oxidation performance compared to the plain α-Fe2 O3 nanostructure on the Fe substrate. The α-Fe2 O3 /FeOOH NFs on Au/Fe photoanode yields a photocurrent density of 3.1 mA cm-2 at 1.5 VRHE , and a remarkably low onset potential of 0.5-0.6 VRHE in 1 m KOH under AM 1.5G (100 mW cm-2 ) simulated sunlight illumination. The enhancement in PEC performance can be attributed to a synergistic effect of the FeOOH top decoration and the Au underlayer, whereby FeOOH facilitates hole transfer at the interface of electrode/electrolyte and the Au layer provides a sink for the electron transport to the back contact. This results in a drastically improved charge-separation efficiency in the single crystalline α-Fe2 O3 NF photoanode.

Introduction of Graphene Oxide as Buffer Layer in Perovskite Solar Cells and the Promotion of Soluble n-Butyl-substituted Copper Phthalocyanine as Efficient Hole Transporting Material

Organometal halide perovskite solar cells have been constructed using soluble tetra-n-butyl-copper phthalocyanine as hole transporting material. Devices were constructed and characterized under ambient conditions of 50–60% ambient humidity. Soluble copper phthalocyanine gave a modest PCE of 7.3% but when a buffer layer of either Al2O3 or graphene oxide was introduced between the perovskite and the hole transporting layer the cell efficiency extensively increased and reached 14.4% in the presence of graphene oxide. Corresponding data obtained by employing the standard spiro-OMeTAD as hole transporter gave equivalent performance. Combination then of tetra-n-butyl-copper phthalocyanine with graphene oxide offers a very good alternative of simpler and stable materials for perovskite solar cell construction. The presently recorded data highlight the role of the buffer layer, especially graphene oxide, as the material which blocks shunt paths and facilitates hole transfer between the perovskite and the hole transporting layer.