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The charge carrier balance in organic light-emitting diodes (OLEDs) is crucial for optimizing external quantum efficiency (EQE). This is typically achieved by using charge injection and blocking layers deposited by vacuum deposition, which increases the fabrication time and cost. This study investigates the potential of polyethylenimine ethoxylated (PEIE), Zinc oxide (ZnO) nanoparticles and a PEIE-ZnO nanocomposite as functional layers for OLEDs with improved electron injection and hole blocking properties fabricated by solution processing. The PEIE-ZnO nanocomposite improves OLED performance: (a) a 28 % increase in current density and enhanced electron mobility, (b) two times increase in electron mobility of the electron injection/transport layer, and (c) a reduction in surface and interface trap density. Consequently, the PEIE-ZnO nanocomposite shows an 84 % increase in electroluminescence, 52.5 % increase in luminous efficacy, 35.5 % increment in external quantum efficiency, and increased stability as measured by degradation studies. Employing these interlayers fabricated by the novel and roll-to-roll compatible Spray-on-Screen deposition technique show a comparable OLED performance as that of spin coated and vacuum deposited electron injection layers, which makes the large area fabrication of optoelectronic devices with high efficiencies, high output, low cost, and long lifetime a possible reality.

In this study, we report 10 cm2 nonfullerene solar cells with power conversion efficiency of 10.24%. The demonstration of the large-area cells is based on the HxMoO3-assisted growth of two silver electrodes, namely, the ultrathin-transparent electrode (on the top) and opaque electrode (at the bottom). The device structure has the configuration glass/HxMoO3/opaque Ag (70 nm)/active layer/HxMoO3/ultrathin Ag (8 nm)/MoO3. The chemically reactive HxMoO3 could react with silver oxide during the growth of the initial few nanometers of silver, as inferred from X-ray spectroscopy measurements. The reaction increases the nucleus sites that assist the continuous and uniform growth of the silver films. The percolation threshold thickness of conductive ultrathin Ag films on HxMoO3 can be as low as 4 nm. The root-mean-square surface roughness of opaque silver (70 nm) grown on the HxMoO3 surface is as low as 1.06 nm. HxMoO3 facilitates the growth of uniform, continuous and smooth silver films that enable the efficient large-area nonfullerene organic solar cells.

There is a great need for flexible and wearable power generators. Wire-shaped thermoelectric (TE) devices provide a solution that can convert waste heat to electricity. Here, meters-long, sewable and wearable conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) wires are fabricated based on the removal of the outer-ring PSS. The wires are sewable and exhibit a conductivity of 1433 S cm−1 at room temperature, a Seebeck coefficient of 21.3 μV K−1 and a power factor (PF) of 65 μW (mK2)−1. The wires have a cross-sectional area of about 570 μm2 and a tensile strength of about 200 MPa, and show stable electrical conductivity in air and under different temperatures. Under a temperature gradient (about 3 K) generated from hands and room temperature, a TE generator with 34 pairs of PEDOT:PSS and copper wires assembled on a fabric outputs a voltage of 2.2 mV. It shows potential for applications in wearable devices.

The electron transporting layer (ETL) is critical for achieving high performance and high stability of non-fullerene organic solar cells. However, the commonly used ZnO ETLs have the disadvantage of poor device photo-stability. Although aqueous SnO2 can yield better stability of devices, an “S” shape is observed in the current density–voltage (J–V) characteristics resulting in poor device performance when it is used as an ETL in non-fullerene organic solar cells. In this paper, we have developed a method of modifying an aqueous SnO2 solution by adding polyethylene oxide (PEO) or polyethylenimine (PEI) to eliminate the “S” shape characteristic of organic solar cells. PEO and PEI can interact with SnO2 to form favorable interface dipoles and reduce the work function of the ETL films, which improves charge collection. In addition, the work function of the PEO or PEI modified SnO2 shows better photo-stability than that of ZnO, and the devices based on the modified SnO2 ETL also achieve higher photo-stability compared to the ZnO reference device.

Preparation of high-quality films plays an important role to achieve high-performance nonfullerene (NF) organic solar cells. NF active layer films are typically fabricated by spin coating. Novel fabrication methods to process the NF active layer are desirable to be compatible with large-area production. Herein, we report on the fabrication of NF active layer films via a water transfer printing method. This method delivers a uniform film with controllable film thicknesses. NF active layers of PDBD-T:ITIC and PBDB-T-2F:IT-4F were fabricated via the method to validate its effectiveness. Solar cells with the water transfer-printed active layers show comparable performance (up to 11.7%) to the cells with spin-coated active layers. Furthermore, NF solar modules containing 4-sub cells with the active area of 3.2 cm2 are also fabricated via the method. The module shows VOC of up to 3.4 V and a power conversion efficiency of 8.1% with the PBDB-T-2F:IT-4F active layer.

The chemical stability of non-fullerene acceptors under acidic and basic environments is important because the printable electrodes and interfacial layers are typically acidic (such as PEDOT:PSS) o...

A low-temperature carbon electrode with good perovskite compatibility is employed in hole-transport-material free perovskite solar cells, and a champion power conversion efficiency (PCE) of 11.7% is obtained. The PCE is enhanced to 14.55% by an interface modification of PEDOT:PSS. The application of this carbon on ITO/PEN substrates is also demonstrated.

ZnO is the dominantly used electron transporting material in high-performance inverted nonfullerene (NF) organic solar cells. Here, we report that nonfullerene acceptors tend to decompose in the presence of ZnO due to its photocatalytic activity under UV illumination. This leads to poor device stability of NF solar cells under solar light illumination. To mitigate this issue, SnO2 is used as an electron-transporting layer that has a wide band gap and is almost irresponsive to the AM1.5 solar spectrum to replace ZnO. NF solar cells with SnO2 display a power conversion efficiency of 14.1% with the PM6:IT-4F active layer and show better device illumination stability than the reference cells with ZnO.

Light weight and excellent mechanical flexibility are the most important advantages of organic solar cells (OSCs), compared with their inorganic counterparts. However, the development of flexible OSCs lags behind the cells fabricated on rigid glass. Herein, we report efficient flexible nonfullerene OSCs with a novel device structure: AgNWs@PI/ZnO/active layer/MoO3/Ag, where AgNWs@PI (silver nanowires embedded in polyimide substrates) is used as the substrate and the bottom electrode. Optimized ZnO processed from isopropyl alcohol (IPA) solutions physically does not destroy/dissolve the PI substrates, and is chemically compatible with the nonfullerene active layer. With PBDB-T-2F:IT-4F as the nonfullerene active layer, the fabricated flexible solar cell displays a power conversion efficiency of 11.6% (VOC = 0.82 V, JSC = 19.6 mA cm−2, and FF = 0.72).

Achieving high power conversion efficiency and good mechanical robustness is still challenging for the ultraflexible organic solar cells. Interlayers simultaneously having good mechanical robustness and good chemical compatibility with the active layer are highly desirable. In this work, we present an interlayer of Zn2+-chelated polyethylenimine (denoted as PEI-Zn), which can endure a maximum bending strain over twice as high as that of ZnO and is chemically compatible with the recently emerging efficient nonfullerene active layers. On 1.3 μm polyethylene naphthalate substrates, ultraflexible nonfullerene solar cells with the PEI-Zn interlayer display a power conversion efficiency of 12.3% on PEDOT:PSS electrodes and 15.0% on AgNWs electrodes. Furthermore, the ultraflexible cells show nearly unchanged power conversion efficiency during 100 continuous compression-flat deformation cycles with a compression ratio of 45%. At the end, the ultraflexible cell is demonstrated to be attached onto the finger joint and displays reversible current output during the finger bending-spreading., Simultaneously achieving high efficiency and mechanical robustness is challenging for ultraflexible organic solar cells. Here, Qin et al. present a robust interlayer of Zinc-chelated polyethylenimine (PEI-Zn) to facilitate the demonstration of efficient and mechanically robust ultraflexible solar cells.

Metal electrode-free organic solar cells with a printable top electrode are attractive in realizing the low cost of photovoltaics. Interaction between the printable electrode and the active layer is critical to the device performance. In this work, we report the chemical interaction between the printable polymer electrode poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and the typically used additive of 1,8-dioodooctane (DIO) in the active layer. DIO can be converted to hydrogen iodide (HI) under the acidic condition of PEDOT:PSS, and the HI chemically reduces the PEDOT:PSS with the appearance of an absorbance band at 800-1100 nm. The generation of I2 is verified by the color change of starch. The reaction results in a decrease of its work function that hinders efficient hole collection. A strategy is proposed to circumvent the detrimental interaction by inserting an ultrathin (15 nm) active layer without DIO between the initial active layer and the PEDOT:PSS electrode. A power conversion efficiency of 10.1% is achieved for the metal electrode-free nonfullerene organic solar cells.

In perovskite solar cells, I- tends to oxidize to I2 due to its low redox potential. The generated I2 has been proved to be detrimental to device performance. Herein, for the first time, an amidine DBU is introduced as an additive into the precursor of the perovskite layer. The reductive DBU can suppress the formation of iodine impurity, resulting in a highly pure perovskite polycrystalline film. The efficiency and stability of the perovskite solar cells are thus improved.

Transfer printing is a powerful technique to deposit films on surfaces that are difficult to fabricate by traditional coating methods (spin coating, inkjet printing). Adhesion tuning between the transferred film and the target surface is critical for successful transfer of the film. Typically, the transfer printing relies on Van der Waals force at the interface. In this work, we engineered an interfacial interaction to assist transfer printing of organic active layers onto the PEI-Zn (electron-transporting layer) by introducing a layer of poly(sodium-4-styrene sulfonate) (PSSNa). The adhesion increases between the active layer and PEI-Zn surface with their contact. Water between the two layers is spontaneously repelled and improves the transfer of active layer onto the PEI-Zn surface. The technique enables the direct fabrication of organic solar cells on curved surfaces. Organic solar cells on a curved vial with power conversion efficiency of 10.8% was demonstrated.

Conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been widely used as a transparent electrode in organic optoelectronics. Patterning of PEDOT:PSS is needed when used in these devices to avoid or alleviate shunt current. In this work, we present a method of patterning PEDOT:PSS films via a two-step process of laser ablation (nanosecond laser, 1064 nm) and acid treatment (phosphoric acid). The PEDOT can be easily removed by the laser ablation, but PSS is not. This is due to the difference of their absorbance. PEDOT has strong absorption at the wavelength of 1064 nm, but PSS is transparent there. The excess insulator PSS residue hinders electron collection in solar cell devices. Acid treatment can efficiently reduce the PSS residue that is confirmed by X-ray photoelectron spectroscopy (XPS) and optical microscope. With the two-step etching process, solar cells with patterned PEDOT:PSS bottom electrode show high fill factor of 69% and power conversion efficiency of 12.4%.

All-solution-processed organic solar cells (from the bottom substrate to the top electrode) are highly desirable for low-cost and ubiquitous applications. However, it is still challenging to fabricate efficient all-solution-processed organic solar cells with a high-performance nonfullerene (NF) active layer. Issues of charge extraction and wetting are persistent at the interface between the nonfullerene active layer and the printable top electrode (PEDOT:PSS). In this work, efficient all-solution-processed NF organic solar cells (from the bottom substrate to the top electrode) are reported via the adoption of a layer of hydrogen molybdenum bronze (HX MoO3 ) between the active layer and the PEDOT:PSS. The dual functions of HX MoO3 include: 1) its deep Fermi level of -5.44 eV can effectively extract holes from the active layer; and 2) the wetting issues of the PEDOT:PSS on the hydrophobic surface of the NF active layer can be solved. Importantly, fine control of the HX MoO3 composition during the synthesis is critical in obtaining processing orthogonality between HX MoO3 and the PEDOT:PSS. Flexible all-solution-processed NF organic solar cells with power conversion efficiencies of 11.9% and 10.3% are obtained for solar cells with an area of 0.04 and 1 cm2 , respectively.

Vertical phase distribution plays an important role in the quasi-two-dimensional perovskite solar cells. So far, the driving force and how to tailor the vertical distribution of layer numbers have been not discussed. In this work, we report that the vertical distribution of layer numbers in the quasi-two-dimensional perovskite films deposited on a hole-transporting layer is different from that on glass substrate. The vertical distribution could be explained by the sedimentation equilibrium because of the colloidal feature of the perovskite precursors. Acid addition will change the precursors from colloid to solution that therefore changes the vertical distribution. A self-assembly layer is used to modify the acidic surface property of the hole-transporting layer that induces the appearance of desired vertical distribution for charge transport. The quasi-two-dimensional perovskite cells with the surface modification display a higher open-circuit voltage and a higher efficiency comparing to reference quasi-two-dimensional cells., Vertical phase distribution of quasi-two-dimensional perovskite plays vital roles in their optoelectronic properties. Here Liu et al. show that surface modification of the hole-transporting layer is an effective approach to control the vertical phase distribution and optimize the device efficiency.

The installation verticality between the optical axis of CCD and the working plane of intelligent laser cutting machine is one of the most important factors in determining image quality of the processed object which comes from computer vision system. In this paper, an innovative method is proposed which can make it possible to use the equipment of own system of intelligent laser cutting machine to detect installation verticality between the optical axis of CCD and the working plane. Experimental results show that the method presented in this paper is a feasible solution for measuring the installation verticality between the optical axis of CCD and the working plane of intelligent laser cutting machine.