Abd. Rashid bin Mohd Yusoff

A high efficiency solution processed polymer inverted triple-junction solar cell exhibiting a power conversion efficiency of 11.83%

High efficiency, solution-deposited polymer inverted double- and triple-junction solar cells are demonstrated. The devices are composed of three distinctive photosensitive materials in three distinct subcells, with minimal absorption spectral overlap, and with a bandgap ranging from 1.3 eV to 1.82 eV. A transparent hybrid inorganic organic mixture was introduced as an interconnecting layer to optically and physically connect the subcells. Accordingly, a power conversion efficiency of 10.39% was attained for the double-junction cell and a record high of 11.83% was obtained for the triple-junction cell.

Au-doped single layer graphene nanoribbons for a record-high efficiency ITO-free tandem polymer solar cell

Polymer solar cells (PSCs) are apparently becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequent use of a transparent conductive electrode, indium-tin-oxide (ITO), in the present PSC technologies has increased the overall expenses. In addition, its brittleness in nature could limit the future development of PSCs, particularly in a flexible format. Here, we report on the development of Au-doped single layer graphene nanoribbons (Au-doped SLGNRs) as an option to the transparent conducting electrode (indium tin oxide, ITO) that could yield a single-layer PSC with power conversion and external quantum efficiencies comparable to commonly used transparent electrodes. When the Au-doped SLGNRs are implemented in tandem architecture, a power conversion efficiency (PCE) of 8.48% is achieved. This is the highest efficiency for ITO-free tandem PSCs to date. The improved performance of the Au-doped SLGNR anode is characterized to the structure of the device that enables a hole transport from the active layer into the Au-doped SLGNR anode.

Stable and null current hysteresis perovskite solar cells based nitrogen doped graphene oxide nanoribbons hole transport layer

Perovskite solar cells are becoming one of the leading technologies to reduce our dependency on traditional power sources. However, the frequently used component poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) has several shortcomings, such as an easily corroded indium-tin-oxide (ITO) interface at elevated temperatures and induced electrical inhomogeneity. Herein, we propose solution-processed nitrogen-doped graphene oxide nanoribbons (NGONRs) as a hole transport layer (HTL) in perovskite solar cells, replacing the conducting polymer PEDOT:PSS. The conversion efficiency of NGONR-based perovskite solar cells has outperformed a control device constructed using PEDOT:PSS. Moreover, our proposed NGONR-based devices also demonstrate a negligible current hysteresis along with improved stability. This work provides an effective route for substituting PEDOT:PSS as the effective HTL.

Inverted quantum-dot light emitting diodes with cesium carbonate doped aluminium-zinc-oxide as the cathode buffer layer for high brightness

We report an inverted structure of quantum-dot light emitting diodes (QLEDs) with cesium carbonate (Cs2CO3) doped aluminum-zinc-oxide (AZO) as the cathode buffer. The Cs2CO3 doped AZO with Cs2CO3 blending ratios (AZO : Cs2CO3) from 4 : 1 to 2 : 1 was used as an electron transport layer in QLEDs. It is found that the conductivity of the AZO : Cs2CO3 blended solution increases with the increase in the concentration of Cs2CO3 until a particular concentration, and the luminance intensity increases sharply from 9949 to 57 350 cd m−2. It is concluded therefore that Cs2CO3 doped AZO could be a good cathode buffer for inverted QLEDs.

Semi-transparent quantum-dot light emitting diodes with an inverted structure

Semi-transparent quantum-dot light-emitting diodes (QLEDs) can open display applications in many areas, such as energy-saving, aircraft lighting, wallpaper technologies and medical devices. In this paper, the first semi-transparent inverted QLED was demonstrated by using red quantum-dot emissive layer (QD EML). Semi-transparent silver was used as a top electrode deposited by thermal evaporation. The maximum luminance of 10540 cd m−2 was achieved for the semi-transparent inverted QLEDs. The optimized QLED has a maximum transparency of ∼45% in the red-emission region.

GO:PEDOT:PSS for High-Performance Green Phosphorescent Organic Light-Emitting Diode

A high-performance green phosphorescent organic light-emitting diode (GPhOLED) based on easily available graphene oxide (GO)-doped poly(styrenesulfonate)-doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) as anode buffer layer and simple device fabricating process has been demonstrated. The GO:PEDOT:PSS-based GPhOLEDs show a better performance compared to the PEDOT:PSS only GPhOLEDs with current and power efficiencies of 52 and 41 cd/A and 36 and 27 lm/W at 1000 cd/m2, respectively. These findings shed new light on the development of high-performance GPhOLEDs.

Null current hysteresis for acetylacetonate electron extraction layer in perovskite solar cells

Solution processed zirconium acetylacetonate (Zr(acac)) is successfully employed as an electron extraction layer, replacing conventional titanium oxide, in planar CH3NH3PbI3 perovskite solar cells. The as-prepared Zr(acac) film possesses high transparency, high conductivity, a smooth morphology, high wettability, compatibility with PbI2 DMF solution, and an energy level matching that of CH3NH3PbI3 perovskite material. An average power conversion efficiency of about 11.93%, along with a high fill factor of 74.36%, an open circuit voltage of 1.03 V, and a short-circuit current density of 15.58 mA cm(-2) is achieved. The overall performance of the devices is slight better than that of cells using ruthenium acetylacetonate (Ru(acac)). The differences between solar cells with different electron extraction layers in charge recombination, charge transport and transfer and lifetime are further explored and it is demonstrate that Zr(acac) is a more effective and promising electron extraction layer. This work provides a simple, and cost effective route for the preparation of an effective hole extraction layer.

Plasmonic organic solar cell employing Au NP:PEDOT:PSS doped rGO

We demonstrate the first facile synthetic process to prepare a highly promising composite material by combining our frequently used p-type conducting polymer poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and reduced graphene oxide (rGO), and further employed the composite as a hole transport layer (HTL) in plasmonic organic solar cells. The conductivity of the PEDOT:PSS:rGO mixture can be tuned by varying the concentration of rGO in the PEDOT:PSS solution. Ultimately, the integration of gold nanoparticles (Au NPs) in the PEDOT:PSS:rGO plasmonic organic solar cell demonstrated a 9.34% improvement in the power conversion efficiency (PCE), measured using an AM1.5 G solar simulator at 100 mW cm−2 light illumination intensity to generate localized surface plasmon resonance (LSPR). The enhanced performance was caused by local enrichment of the electromagnetic field surrounding the Au NPs.

Organic devices based on nickel nanowires transparent electrode

Herein, we demonstrate a facile approach to synthesize long nickel nanowires and discuss its suitability to replace our commonly used transparent electrode, indium-tin-oxide (ITO), by a hydrazine hydrate reduction method where nickel ions are reduced to nickel atoms in an alkaline solution. The highly purified nickel nanowires show high transparency within the visible region, although the sheet resistance is slightly larger compared to that of our frequently used transparent electrode, ITO. A comparison study on organic light emitting diodes and organic solar cells, using commercially available ITO, silver nanowires, and nickel nanowires, are also discussed.

Photovoltaic devices with a PEDOT:PSS:WOx hole transport layer

In this paper, we report a significantly improved fill factor (FF) of inverted poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) organic photovoltaic devices via surface modification. The influence of the poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) hole extraction layer (HEL) modified with tungsten oxide (WOx) on inverted organic photovoltaics is studied. It is demonstrated that the PEDOT:PSS:WOx modification leads to a remarkably high FF, while abruptly reducing the series resistance and at the same time increasing the shunt resistance. The efficiency increased from 3.93 to 5.37%, and it is demonstrated that PEDOT:PSS modified with WOx HEL is an attractive material for high performance organic photovoltaic devices.