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In this work, the enhanced performance of inverted bulk heterojunction (BHJ) organic solar cells (OSCs) using zinc oxide (ZnO):polyoxometalate (POM), in particular sodium metatungstate (Na6H2W12O40), nanocomposite films as electron extraction layers (EELs) is demonstrated. The addition in the precursor solution of ZnO of sodium metatungstate results in the formation of ZnO:ZnWO4 nanocomposite as evidenced by X-ray diffraction, Fourier transform infrared and photoluminescence measurements. The formation of ZnO:ZnWO4 heterointerface reduces the work function of the nanocomposite material leading to a more favorable electron extraction/transport at the organic blend/electron transport layer interface. Additionaly, the amount of zinc interstitial defects is suppressed having a profound positive effect on device stability. As a result, simultaneously improved open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF) are obtained in the devices using the ZnO :ZnWO 4 nanocomposites. Therefore, both of the inverted BHJ OSCs composed of either poly (3-hexylthiophene) (P3HT):[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) or P3HT:indene-C60 bisadduct (IC60BA) photoactive blends show a significant performance enhancement when using the nanocomposite electron extraction layer, exhibiting a 27% and 23%, respectively, improvement in their power conversion efficiency (PCE) values compared to the reference devices based on pristine ZnO. In addition, the devices with the ZnO :ZnWO 4 layer exhibit a remarkable stability enhancement retaining 95% of their initial PCE value upon storage for 500 h.

Organic solar cells based on nonfullerene acceptors have recently witnessed a significant rise in their power conversion efficiency values. However, they still suffer from severe instability issues, especially in an inverted device architecture based on the zinc oxide bottom electron transport layers. In this work, we insert a pyrene-bodipy donor-acceptor dye as a thin interlayer at the photoactive layer/zinc oxide interface to suppress the degradation reaction of the nonfullerene acceptor caused by the photocatalytic activity of zinc oxide. In particular, the pyrene-bodipy-based interlayer inhibits the direct contact between the nonfullerene acceptor and zinc oxide hence preventing the decomposition of the former by zinc oxide under illumination with UV light. As a result, the device photostability was significantly improved. The

Photovoltaic devices based on organic semiconductors and organo-metal halide perovskites have not yet reached the theoretically predicted power conversion efficiencies while they still exhibit poor environmental stability. Interfacial engineering using suitable materials has been recognized as an attractive approach to tackle the above issues. We introduce here a zinc porphyrin-triazine-bodipy donor-π bridge-acceptor dye as a universal electron transfer mediator in both organic and perovskite solar cells. Thanks to its "push-pull" character, this dye enhances electron transfer from the absorber layer toward the electron-selective contact, thus improving the device's photocurrent and efficiency. The direct result is more than 10% average power conversion efficiency enhancement in both fullerene-based (from 8.65 to 9.80%) and non-fullerene-based (from 7.71 to 8.73%) organic solar cells as well as in perovskite ones (from 14.56 to 15.67%), proving the universality of our approach. Concurrently, by forming a hydrophobic network on the surface of metal oxide substrates, it improves the nanomorphology of the photoactive overlayer and contributes to efficiency stabilization. The fabricated devices of both kinds preserved more than 85% of their efficiency upon exposure to ambient conditions for more than 600 h without any encapsulation.

Here, we use a simple and effective method to accomplish energy level alignment and thus electron injection barrier control in organic light emitting diodes (OLEDs) with a conventional architecture based on a green emissive copolymer. In particular, a series of functionalized zinc porphyrin compounds bearing π-delocalized triazine electron withdrawing spacers for efficient intramolecular electron transfer and different terminal groups such as glycine moieties in their peripheral substitutes are employed as thin interlayers at the emissive layer/Al (cathode) interface to realize efficient electron injection/transport. The effects of spatial (i.e., assembly) configuration, molecular dipole moment and type of peripheral group termination on the optical properties and energy level tuning are investigated by steady-state and time-resolved photoluminescence spectroscopy in F8BT/porphyrin films, by photovoltage measurements in OLED devices and by surface work function measurements in Al electrodes modified with the functionalized zinc porphyrins. The performance of OLEDs is significantly improved upon using the functionalized porphyrin interlayers with the recorded luminance of the devices to reach values 1 order of magnitude higher than that of the reference diode without any electron injection/transport interlayer.

Motivated by the excellent electron-transfer capability of porphyrin molecules in natural photosynthesis, we introduce here the first application of a porphyrin compound to improve the performance of planar perovskite solar cells. The insertion of a thin layer consisting of a triazine-substituted Zn porphyrin between the TiO2 electron transport layer and the CH3NH3PbI3 perovskite film significantly augmented electron transfer toward TiO2 while also sufficiently improved the morphology of the perovskite film. The devices employing porphyrin-modified TiO2 exhibited a significant increase in the short-circuit current densities and a small increase in the fill factor. As a result, they delivered a maximum power conversion efficiency (PCE) of 16.87% (average 14.33%), which represents a 12% enhancement compared to 15.01% (average 12.53%) of the reference cell. Moreover, the porphyrin-modified cells exhibited improved hysteretic behavior and a higher stabilized power output of 14.40% compared to 10.70% of the re...

In the present work, we effectively modify the TiO2 electron transport layer of organic solar cells with an inverted architecture using appropriately engineered porphyrin molecules. The results show that the optimized porphyrin modifier bearing two carboxylic acids as the anchoring groups and a triazine electron-withdrawing spacer significantly reduces the work function of TiO2, thereby reducing the electron extraction barrier. Moreover, the lower surface energy of the porphyrin-modified substrate results in better physical compatibility between the latter and the photoactive blend. Upon employing porphyrin-modified TiO2 electron transport layers in PTB7:PC71BM-based organic solar cells we obtained an improved average power conversion efficiency up to 8.73%. Importantly, porphyrin modification significantly increased the lifetime of the devices, which retained 80% of their initial efficiency after 500 h of storage in the dark. Because of its simplicity and efficacy, this approach should give tantalizing g...

Combining high efficiency and long lifetime under ambient conditions still poses a major challenge towards commercialization of polymer solar cells. Here we report a facile strategy that can simultaneously enhance the efficiency and temporal stability of inverted photovoltaic architectures. Inclusion of a silanol-functionalized organic–inorganic hybrid polyoxometalate derived from a PW9O34 lacunary phosphotungstate anion, namely (nBu4N)3[PW9O34(tBuSiOH)3], significantly increases the effectiveness of the electron collecting interface, which consists of a metal oxide such as titanium dioxide or zinc oxide, and leads to a high efficiency of 6.51% for single-junction structures based on poly(3-hexylthiophene):indene-C60 bisadduct (P3HT:IC60BA) blends. The above favourable outcome stems from a large decrease in the work function, an effective surface passivation and a decrease in the surface energy of metal oxides which synergistically result in the outstanding electron transfer mediating capability of the functionalized polyoxometalate. In addition, the insertion of a silanol-functionalized polyoxometalate layer significantly enhances the ambient stability of unencapsulated devices which retain nearly 90% of their original efficiencies (T90) after 1000 hours. published

In this work, we propose a simple and effective approach to modify the optoelectronic properties of the commonly used poly(3,4-ethylenedioxylthiophene):poly(styrene sulfonate) (PEDOT:PSS) and consequently to improve hole injection and transport in organic light emitting diodes (OLEDs) using emissive layers based on a fluorescence copolymer. In particular, two triphenylsulfonium (TPS) salts that consist of the same TPS cation and two different counter anions, in particular, hexafluoroantimonate (SbF6) and trifluoromethane sulfonate (Triflate) were added in the PEDOT:PSS solution in various concentrations and the composite films were fully characterized for surface and optoelectronic properties and subsequently we employed as hole injection layers (HILs) in OLEDs. It is demonstrated that both, the counter anion and the concentration of TPS-salts in the PEDOT:PSS matrix play significant role in the optoelectronic properties of the composite and thus in the device performance. Although all TPS-salt modified PEDOT:PSS films exhibited higher work function (WF) values relative to the undoped one thus resulting in more efficient hole injection than pristine PEDOT:PSS, the PEDOT:PSS:TPS-Triflate with the lower concentration (10:1 v/v) showed the highest luminous (LE) and power efficiency (PE) values of 27.04 cd A−1 and 6.26 lm W−1, respectively. This extraordinary performance was ascribed to a significant increase in the conductivity of the composite film combined with the formation of an interface exciplex between the TPS-Triflate (acceptor) and the emissive copolymer (donor). This interfacial electroplex strongly confines the generated excitons and prevents their diffusion towards aluminum cathode which acts as exciton quencher.

The design and development of novel materials with superior charge transport capabilities plays an essential role for advancing the performance of electronic devices. Ternary and doped oxides can be potentially explored because of their tailored electronic energy levels, exceptional physical properties, high electrical conductivity, excellent robustness and enhanced chemical stability. Here, a route for improving metal oxide characteristics is proposed by preparing a novel ternary oxide, namely, carbon-doped tantalum dioxyfluoride (TaO2FCx) through a straightforward synthetic route and exploring its effectiveness as an electron transport material in optoelectronic devices based on organic semiconductors. Among other devices, we fabricated fluorescent green organic light emitting diodes with current efficiencies of 16.53 cd/A and single-junction non-fullerene organic solar cells reaching power conversion efficiencies of 14.14% when using the novel oxide as electron transport material. Our devices also exhibited the additional advantage of high operational and temporal stability. Non-fullerene OSCs based on the novel compound showed unprecedented stability when exposed to UV light in air due to the non-defective nature of TaO2FCx. We employed a tank of experiments combined with theoretical calculations to unravel the performance merits of this novel compound. This study reveals that properly engineered ternary oxides, in particular, TaO2FCx or analogous materials can enable efficient electron transport in organic optoelectronics and are proposed as an attractive route for the broader field of optoelectronic devices including metal-organic perovskite, colloidal quantum dot and silicon optoelectronics.