MoO3 buffer layer effect on photovoltaic properties of interpenetrating heterojunction type organic solar cells

Photovoltaic cells, with a conducting polymer/fullerene (C₆₀) interpenetrating heterojunction structure fabricated by spin-coating a conducting polymer onto a C₆₀ thin film, have been investigated and demonstrated a high efficiency as solar cells based on organic materials. The photovoltaic properties of the solar cells with a structure of indium-tin-oxide (ITO)/C₆₀/poly(3-hexylthiophene) (PAT6)/Au have been improved by the insertion of a molybdenum trioxide (VI) (MoO₃) layer as a cathode buffer layer. In the solar cells with the structure of ITO/C₆₀/PAT6/MoO₃/Au, the energy conversion efficiency has been improved to 1.15% under AM1.5 (100 mW/cm²) illumination.     

Metal-free indoline dye sensitized zinc oxide nanowires solar cell

Dye sensitized solar cell (DSSC) based on metal-free indoline dye D102 sensitized zinc oxide (ZnO) nanowires (NWs) derived from aqueous solution on seeded substrate was investigated. The morphology, composition and crystalline structure of the highly oriented ZnO NWs were characterized by field-emission scanning electron microscope, energy dispersive X-ray spectrum spectroscopy and X-ray diffraction, respectively. The chemical bond between D102 and ZnO NWs was confirmed by Fourier transfer infrared spectra. The photovoltaic property of DSSC was characterized at full sun intensity of 100 mW/cm² (AM 1.5) with short circuit current J_sc = 14.06 mA/cm² and energy conversion efficiency η = 2.6%.     

A solution-processable D–A–D small molecule based on isoindigo for organic solar cells

A new linear D–A–D organic small molecule (M1), with triphenylamine as electron donor (D) unit and isoindigo (ID) as electron acceptor (A) unit, was synthesized by Stille coupling reactions. It exhibits broad and strong absorption (300–700 nm), a relatively low HOMO energy level (?5.30 eV), low band gap (1.69 eV), and moderate hole mobility (2.49×10^?4 cm²/Vs). Solution-processed small molecule bulk-heterojunction solar cells based on M1: PC₆₁BM (1:3, w/w) blend film exhibits a power conversion efficiency of 0.84 % with an open-circuit voltage (V _oc) of 0.78 V, under the illumination of AM1.5, 100 mW/cm².     

Two polymeric metal complexes based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) in the backbone: Synthesis,characterization and photovoltaic applications

Two novel polymeric metal complexes PZn(Q)₂–C and PNi(Q)₂–C based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) were synthesized and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. They possess moderate thermal stability and good open-circuit voltages, and the power conversion efficiency of them reached to 1.11% and 0.45%, respectively, under simulated AM 1.5 G solar irradiation (100 mW cm⁻²), which shows a new strategy to design photosensitizers for DSSCs.     

Radiation Resistance of α-Si:H/Si Heterojunction Solar Cells with a Thin <Emphasis Type="Italic">i</Emphasis>-α-Si:H Inner Layer

We have studied the degradation of photoelectric characteristics of heterojunction solar cell samples based on α-Si:H/Si structures upon irradiation by electrons with an energy of 3.8 MeV and fluences of 1 × 10¹²–1 × 10¹⁴ cm^–2. It is shown that the efficiency of the samples of heterojunction solar cell elements under the conditions of AM0 illumination (0.136 W/cm²) is reduced by 25% at a fluence of 2 × 10¹³ cm^–2. This is more than an order of magnitude higher than the critical fluence value achieved previously when silicon solar cells with a p–n junction and an n-type base were irradiated by high-energy electrons.     

Cu2ZnSnS4 solar cells prepared with sulphurized dc-sputtered stacked metallic precursors

In the present work we report the details of the preparation and characterization results of Cu₂ZnSnS₄ (CZTS) based solar cells. The CZTS absorber was obtained by sulphurization of dc magnetron sputtered Zn/Sn/Cu precursor layers. The morphology, composition and structure of the absorber layer were studied by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and Raman scattering. The majority carrier type was identified via a hot point probe analysis. The hole density, space charge region width and band gap energy were estimated from the external quantum efficiency measurements. A MoS₂ layer that formed during the sulphurization process was also identified and analyzed in this work. The solar cells had the following structure: soda lime glass/Mo/CZTS/CdS/i-ZnO/ZnO:Al/Al grid. The best solar cell showed an open-circuit voltage of 345 mV, a short-circuit current density of 4.42 mA/cm², a fill factor of 44.29% and an efficiency of 0.68% under illumination in simulated standard test conditions: AM 1.5 and 100 mW/cm².     

Influence of dopant and polymeric matrix on Indium tin oxide/p-zinc phtalocyanine/n-Si hybrid solar cells

The present paper reports on the photovoltaic properties of zinc phthalocyanine (ZnPc) films with various dopants sandwiched between indium tin oxide (ITO) and n-type silicon substrate. The ZnPc films were realized by entrapping the molecules in a poly(methyl methacrylate) matrix upon stirring and heating the components in solution. For the ITO/p-ZnPc/n-Si sandwich structure solar cells with ZnPc doped with I₂ and without post-annealing, the measured short-circuit current density, open-circuit voltage, maximum output power, fill factor and efficiency were 28.8 mA/cm², 0.46 V, 5.55 mW/cm², 0.42 and 5.55%, respectively, under AM 1.5 illumination.     

Growth of ZnSiP2 from tin solution and temperature composition diagram of the ZnSiP2: Sn system

ZnSiP₂ crystals (1 cm or more in length) have been grown from tin solution on a reproducible basis. The dimensions of the largest crystals obtained were 1.7×0.25×0.03 cm³ and 2×0.1×0.02 cm³. The temperature of the reaction region was 1050 to 1080° C and the cooling rate used to form these crystals was 7.5°C h^–1.A practical temperature-composition section of the ZnSiP₂:Sn phase diagram has been determined by differential thermal analysis, X-ray diffraction measurements and microscopic studies. The resulting information on the liquidus temperature variation with composition served to give better control of ZnSiP₂ growth from tin solution. It was concluded that ZnSiP₂ reacted eutectically with Sn and the eutectic composition was close to 100%.     

Multi-layered TiO2 nanostructured films for dye-sensitized solar cells

Multi-layered TiO₂ nanostructured films were fabricated to improve the light harvest efficiency of the dye-adsorbed TiO₂ electrode in dye-sensitized solar cells (DSSCs) by light scattering. Three different structures of TiO₂ electrodes, with layers consisting of TiO₂ pastes with average diameters of 9, 20, and 300 nm, respectively, were fabricated and their photovoltaic effects on the DSSC devices were investigated. By utilizing the multi-layered TiO₂ electrode constructed using the three different TiO₂ pastes, the overall power conversion efficiency of the DSSC devices in the PEG-based electrolyte was increased to 5.24% under irradiation of 100 mW/cm² at AM 1.5.     

Solid state dye-sensitized solar cell with TiO2/NiO heterojunction: Effect of particle size and layer thickness on photovoltaic performance

The present work demonstrates the usefulness of nickel oxide as a hole transporting material in solid state dye-sensitized solar cells (SSDSSCs). We report on the photovoltaic performances of sensitized TiO₂/NiO heterojunctions, and demonstrate that the TiO₂ film thickness and morphology, as well as NiO film thickness, have significant effects on the photovoltaic behaviour of TiO₂/NiO SSDSSC. Under 1 sun AM1.5G simulated illumination, the SSDSSCs demonstrated best photovoltaic performance with a short circuit photocurrent density, open circuit voltage, fill factor and efficiency of 0.91 mA cm⁻², 780 mV, 40% and 0.3%, respectively. This study draws attention to the feasibility of enhancing the photovoltaic performance in SSDSSC devices through development of appropriately designed sensitized TiO₂/NiO heterojunctions.     

In situ 3-hexylthiophene polymerization onto surface of TiO<Subscript>2</Subscript> based hybrid solar cells

A novel configuration of hybrid solar cells fabricated using TiO₂ and in situ polymerization of poly(3-hexylthiophene), or P3HT, on the surface of TiO₂ is reported. Comparison of UV–Vis absorption and current/voltage (I/V) characteristics of devices with or without in situ polymerized P3HT layer were discussed, and the surface morphology of TiO₂/in situ polymerized P3HT film was investigated by AFM in the contact mode. The short-circuit current density and energy conversion efficiencies of device with in situ polymerized P3HT layer were higher by 6 times and 3 times compared to that of device without the in situ polymerized P3HT layer. By adding poly (ethylene dioxythiophene)-poly (styrene sulfonic acid)(PEDOT-PSS) layer under the top contact, device showed a short-circuit current density of 1.27 mA cm⁻², an open-circuit voltage of 0.52 V, a fill factor of 0.24, and a energy conversion efficiency of 0.16% at AM 1.5 solar illumination (100 mW cm⁻²).     

Heteroepitaxial growth of Si on ZnSiP2

Silicon layers were deposited epitaxially on natural facets of solution-grown ZnSiP₂ crystals by hydrogen reduction of SiHCl₃. Orientation relationships between the diamondstructured layer and the chalcopyrite type substrate were determined giving the results: (112) ZnSiP₂ parallel to (111) Si and (101) ZnSiP₂ parallel to (201) Si. Structural and some electrical properties of the heterojunctions were investigated. Considerations concerning the misfit dislocations are presented.     

Organic solar cells with p-type amorphous chromium oxide thin film as hole-transporting layer

Efficient organic solar cells based on the blends of poly (3-hexylthiophene) (P3HT):fullerene derivative [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) composites have been fabricated by using the sputtered amorphous chromium oxide (ACO) film on fluorine-doped tin oxide (FTO) coated glass substrates as a hole-transporting layer (HTL). Through ACO layer sputtering temperature, film thickness and oxygen flow ratio optimization, the highest power conversion efficiency of 3.28% of FTO/ACO/P3HT:PCBM/Al solar cells on glass has been achieved under AM1.5G 100 mW/cm² illumination. It is found that the device with 10 nm thick ACO sputtered at 473 K and oxygen flow ratio f(O₂) (O₂/O₂ + Ar) = 40% shows the best photovoltaic properties. The photovoltaic properties in these devices are discussed in terms of the band diagrams and series resistance of the devices, and characteristics of ACO HTL. It is concluded that ACO is a suitable alternative to poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as a HTL.     

Simple indoline based donor–acceptor dye for high efficiency dye-sensitized solar cells

A simple metal-free donor–acceptor type sensitizer U01, bearing strong electron donor indoline-triphenylamine was synthesized for panchromatic sensitization of TiO₂ nanocrystalline film. Photovoltaic properties of U01 showed remarkably enhanced light harvesting due to the presence of strong electron donor and robust structure. The new U01 sensitized solar cell exhibited a photovoltaic performance: a short-circuit photocurrent density (J_sc) of 10.70 mA cm⁻², an open-circuit photovoltage (V_oc) of 0.758 V and a fill factor (FF) of 0.74, corresponding to an overall conversion efficiency of 6.01% under standard global AM 1.5 solar light condition. Our results suggest that indoline-triphenylamine based robust D–A molecular architecture is a highly promising class of panchromatic sensitizers for improvement of the performance of dye-sensitized solar cells (DSCs).     

Design and fabrication of InxGa1 − xN/GaN solar cells with a multiple-quantum-well structure on SiCN/Si(111) substrates

The fabrication and characterization of In_xGa_1 − xN/GaN-based solar cells that use In_xGa_1 − xN multiple quantum wells (MQWs) and a SiCN/Si(111) substrate are reported. Solar cell operation with a low dark current density (J_d), a high open-circuit voltage (V_oc), a high short-circuit current density (J_sc), and a high fill factor (FF) is demonstrated. It was found that the proposed device and fabrication technology are applicable to the realization of solar cells with a low J_d of 2.14 to 8.88 μA/cm², a high V_oc of 2.72 to 2.92 V, a high J_sc of 2.72 to 2.97 mA/cm², and a high FF of 61.51 to 74.89%. The device performance with various quantum-well configurations was investigated under an air mass 1.5 global solar spectrum. A high photovoltaic efficiency of 5.95% in the MQW sample over the p-i-n sample was observed.     

Heterojunction solar cells with integrated Si and ZnO nanowires and a chalcopyrite thin film

ZnO nanowires (NWs) have been successfully synthesized using a hydrothermal technique on both glass and silicon substrates initially coated with a sputtered ZnO thin film layer. Varying ZnO seed layer thicknesses were deposited to determine the effect of seed layer thickness on the quality of ZnO NW growth. The effect of growth time on the formation of ZnO NWs was also studied. Experimental results show that these two parameters have an important effect on formation, homogeneity and vertical orientation of ZnO NWs. Silicon nanowires were synthesized by a Ag-assisted electroless etching technique on an n-type Si (100) wafer. SEM observations have revealed the formation of vertically-aligned Si NWs with etching depth of ∼700 nm distributed over the surface of the Si. An electron-beam evaporated chalcopyrite thin film consisting of p-type AgGa_0.5In_0.5Se₂ with ∼800 nm thickness was deposited on the n-type ZnO and Si NWs for the construction of nanowire based heterojunction solar cells. For the Si NW based solar cell, from a partially illuminated area of the solar cell, the open-circuit voltage, short-circuit current density, fill factor and power conversion efficiency were 0.34 V, 25.38 mA cm⁻², 63% and 5.50%, respectively. On the other hand, these respective parameters were 0.26 V, 3.18 mA cm⁻², 35% and 0.37% for the ZnO NW solar cell.     

Versatile preparation method for mesoporous TiO2 electrodes suitable for solid-state dye sensitized photocells

Nano-structured TiO₂ electrodes, suitable for dye sensitized solid-state solar cells were prepared by a new simple spraying technique (SPT). Physical properties of these electrodes were compared with the electrodes prepared by the ‘doctor blade’ technique (typical sliding method, DB). Dye sensitized solid-state solar cells, comprising of CuI as the hole conductor, were fabricated with these electrodes and enhanced photo responses were obtained with SPT electrodes. The effects of additives, either to the spray solution or to the hole conductor on the photoresponses of the above devices were also studied. The cells fabricated with SPT electrodes containing Al(BuⁱO)₃ showed ∼ 2.4% efficiency and addition of 1-ethyl-3-methyl imidazolium thiocyanate into CuI layer further enhanced the efficiency up to 2.75% under the irradiance of 100 mW cm⁻² (AM 1.5).     

Single-Crystal Nanowire Cesium Tin Triiodide Perovskite Solar Cell

This work reports for the first time a highly efficient single-crystal cesium tin triiodide (CsSnI₃) perovskite nanowire solar cell. With a perfect lattice structure, low carrier trap density (≈5 × 10¹⁰ cm⁻³), long carrier lifetime (46.7 ns), and excellent carrier mobility (>600 cm² V⁻¹ s⁻¹), single-crystal CsSnI₃ perovskite nanowires enable a very attractive feature for flexible perovskite photovoltaics to power active micro-scale electronic devices. Using CsSnI₃ single-crystal nanowire in conjunction with highly conductive wide bandgap semiconductors as front-surface-field layers, an unprecedented efficiency of 11.7% under AM 1.5G illumination is achieved. This work demonstrates the feasibility of all-inorganic tin-based perovskite solar cells via crystallinity and device-structure improvement for the high-performance, and thus paves the way for the energy supply to flexible wearable devices in the future.     

Synthesis and optimization of P(MMA-BA-MAA)/PEG-based polymer gel electrolytes

A polymer gel electrolyte based on poly(methyl methacrylate-butyl acrylate-methacrylic acid)/polyethylene glycol 400 blend (P(MMA-BA-MAA)/PEG400) was successfully prepared by a simple and efficient procedure. The optimal ionic conductivity was achieved to be 3.12 mS cm^?1 at the temperature of 30 °C when the electrolyte has the composition of 20 wt% P(MMA-BA-MAA)/PEG400 blend, 0.6 M NaI, and 0.06 M I₂ in the solvent γ-butyrolactone (GBL). For tuning the ionic conductivity, various additives were introduced into the polymer gel electrolytes. The measured values of open circuit voltage, short circuit current, and total photovoltaic efficiency indicates that the adding of pyridine (PY) leads to better performance of the final dye-sensitized solar cells (DSSCs), while the adding of Guanidine thiocyante (GuSCN) leads to a worse one. 4-Tert-butylpyridine (TBP) additive takes a more complex effect on the performance of the final DSSCs. For polymer gel electrolyte with 0.5 M pyridine, the final fabricated dye-sensitized solar cell has overall energy conversion efficiency (η) of 3.63 % (0.16 cm² active area) under AM 1.5 at irradiation of 100 mW cm^?2, which reached the level of the liquid electrolyte based device (η = 3.83 % at 0.16 cm² active area). Meanwhile, this gel electrolyte exhibits well long-term stability. The mechanism analysis revealed the dependences of ionic conductivity on the concentration of polymer and NaI and the temperatures.     

Ferroelectric BiFeO3 as an Oxide Dye in Highly Tunable Mesoporous All‐Oxide Photovoltaic Heterojunctions

As potential photovoltaic materials, transition‐metal oxides such as BiFeO₃ (BFO) are capable of absorbing a substantial portion of solar light and incorporating ferroic orders into solar cells with enhanced performance. But the photovoltaic application of BFO has been hindered by low energy‐conversion efficiency due to poor carrier transport and collection. In this work, a new approach of utilizing BFO as a light‐absorbing sensitizer is developed to interface with charge‐transporting TiO₂ nanoparticles. This mesoporous all‐oxide architecture, similar to that of dye‐sensitized solar cells, can effectively facilitate the extraction of photocarriers. Under the standard AM1.5 (100 mW cm^?2) irradiation, the optimized cell shows an open‐circuit voltage of 0.67 V, which can be enhanced to 1.0 V by tailoring the bias history. A fill factor of 55% is achieved, which is much higher than those in previous reports on BFO‐based photovoltaic devices. The results provide here a new viable approach toward developing highly tunable and stable photovoltaic devices based on ferroelectric transition‐metal oxides.