Improving the Efficiency of ZnO-Based Organic Solar Cell by Self-Assembled Monolayer Assisted Modulation on the Properties of ZnO Acceptor Layer

In this study, we fabricated a bilayer hybrid organic solar cell with P3HT as the donor and ZnO as the acceptor (ITO/ZnO/P3HT/Au). We show that passivating a self-assembled monolayer (SAM) over the ITO electrode surface before fabricating the ZnO layer improves the crystallinity of the ZnO layer and of the P3HT layer spin-coated on top of the ZnO layer. The SAM modification resulted in improved charge mobility in the ZnO and P3HT layers. As a consequence, the short circuit current of the photovoltaic device were enhanced. The power conversion efficiency of the SAM-modified device was approximately 60% higher than that of the untreated device. Our findings suggest that the performance of metal oxide-based organic solar cells can be improved by SAM-assisted modulation of metal oxide crystallinity

Fully Ambient-Processed Perovskite Film for Perovskite Solar Cells: Effect of Solvent Polarity on Lead Iodide

Fully ambient-processed and highly efficient methylammonium lead iodide (MAPbI₃) perovskite films are very desirable for industrial manufacturing of perovskite solar cells (PSCs). To date, most reported highly efficient MAPbI₃ PSCs rely on the fabrication of lead iodide (PbI₂) films inside the glovebox. Here we report a simple fabrication method using extra dry isopropanol (IPA100) for obtaining uniform and loosely packed PbI₂ film, which leads to a uniform and highly crystalline MAPbI₃ film under ambient conditions. Compared with recently reported results (10%–15%) using IPA treatment in the glovebox, we achieved over 16% efficiency of PSCs while fabricating perovskite films in fully ambient conditions. We have found the removal of even trace amounts of water from IPA to be a key factor for the successful ambient fabrication of PbI₂ films, as the high polarity of water negatively influences the crystallinity and morphology of the PbI₂ film

Location-Selective Work Function Engineering by Self-Assembled Monolayers

Control over specific interfaces in devices represents a key challenge for modern organic electronics and photovoltaics. Such control is frequently gained by the use of self-assembled monolayers (SAMs), which, by selection of a proper anchoring group, are generally discriminative with respect to different materials but are not selective between different areas of the same material. In particular, selective tailoring of the work function may be useful for different functional devices in a circuit. Here we demonstrate an approach for solving this problem, opening a way to function-selective electrostatic engineering of chemically identical areas, such as source and drain electrodes in a specific type of organic transistor and, more importantly, the electrodes in different types of organic devices, such as p- and n-channel transistors, located on the same circuitry board. The approach is based on the ultraviolet-light-promoted exchange reaction of SAMs on gold, a standard electrode material in organic electronics

Highly Stable Copper Nanowire-Based Transparent Conducting Electrode Utilizing Polyimide as a Protective Layer

We report the significant improvement of the stability of a copper nanowire (Cu NW)-based transparent conducting electrode (TCE). Our study confirms that in contrast to the common use of poly(vinyl pyrrolidone) (PVP) as a surface passivation agent, PVP facilitates the surface oxidation of CuNWs, which, in turn, severely affects the stability and performance of TCEs. To mitigate this issue, polyimide (CPI) is used as a protective layer for the fabrication of the Cu NW TCEs in the absence of PVP, which shows exceptional stability. The conductivity (resistivity) measurement confirms the stability of TCEs over a period of 90 days without any major degradation, while the conductivity of the reference TCE degrades completely after ∼15 days. In addition, we also demonstrate the device application of our Cu NW TCEs by fabricating a thin-film transistor (TFT) and an organic solar cell showing good operational stability. This study provides an insight into the role of PVP in the poor stability of Cu NWs and offers an alternative for the fabrication of Cu NW-based TCEs with improved stability

Self-Assembled Monolayer Immobilized Gold Nanoparticles for Plasmonic Effects in Small Molecule Organic Photovoltaic

The aim of this study was to investigate the effect of gold nanoparticle (Au NP)-induced surface plasmons on the performance of organic photovoltaics (OPVs) that consist of copper phthalocyanine and fullerene as the active materials. The photon absorption can be enhanced by immobilization of surfactant-stabilized Au NPs on a self-assembled monolayer-modified indium tin oxide (ITO) electrode, and thus, the photocurrent as well as the power conversion efficiency (PCE) of these OPVs can be improved. Varying the density of the immobilized Au NPs in the devices provided no significant variation in the charge mobility but it did enhance the photocurrent. In addition, device simulation results demonstrated that the improvement in photocurrent was due to the enhancement of light absorption and the increase in charge separation, which was facilitated by the Au NPs. Overall, we attributed the improvement in PCE of OPVs to a localized surface plasmon resonance effect generated by the Au NPs

A Bifunctional Copolymer Additive to Utilize Photoenergy Transfer and To Improve Hole Mobility for Organic Ternary Bulk-Heterojunction Solar Cell

To realize the high efficiency organic photovoltaics (OPVs), two critical requirements have to be fulfilled: (1) increasing the photon energy absorption range of the active layer, and (2) improving charge separation and transport in the active layer. This study reports the utilization of THC8, a novel fluorescence-based polymer containing propeller-shaped di-triarylamine and fluorene moieties in the active layer consisting of poly-3-hexylthiophene and [6,6]-phenyl-C61-butyric acid methyl ester to form a ternary bulk heterojunction. The results showed that the high absorbance and strong fluorescence of THC8 at 420 and 510 nm, respectively, broadened the spectral absorption of the OPV, possibly through Förster resonance energy transfer. In addition, the morphology of the device active layer was improved with the addition of a suitable amount of THC8. Consequently, the charge transport property of the active layer was improved. The best power conversion efficiency (PCE) of the device with THC8 was 3.88%, a 25% increase compared to the PCE of a pristine OPV