High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes

High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ～0.15 V, a short circuit current of ～275.0 pA, and an energy conversion efficiency of up to ～1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.     

Quantum junction solar cells

Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics.     

Alloyed inversion layer solar cells with n-Si substrates and TiOx antireflection coatings

Minority carrier inversion layer solar cells on n-type single-crystal silicon substrates have been fabricated. The photovoltaic structure used consists of a p⁺ −n alloyed aluminium grid pattern with a layer of chemically vapour-deposited titanium oxide as the antireflection coating. The titanium oxide layer contains negative charges (of the order of 10¹² cm⁻²) which can induce positive charges (holes) on the silicon surface and so cause inversion of the n-type substrate. A back surface field is obtained by heavily doping the back surface of the substrate with phosphorous which also provides the ohmic contact.An air mass 1 active area efficiency of 15.7% (13.6% total area efficiency) has been achieved with a 133 μm grid spacing on a 10–20 Ω cm polished single-crystal material. Similar efficiencies have also been obtained from rough-surface cells (i.e. with unpolished silicon surfaces).     

Copper phthalocyanine based Schottky diode solar cells

Copper phthalocyanine (CuPc)/Aluminum (Al) Schottky diode solar cells were studied. The thickness of the CuPc layer was varied from 15 nm to 140 nm. Short circuit current densities (J_sc) increased with thickness from 0.042 mA/cm² at 15 nm to 0.124 mA/cm² at 120 nm reaching saturation at that level. Open circuit voltages (V_oc) increased from 220 mV at 15 nm to 907 mV at 140 nm. Analysis of the current-voltage characteristics indicated that tunneling and interface recombination current mechanisms are important components of the current transport at the CuPc/Al junction.     

Study on the bulk junction type organic solar cells with double zinc oxide layer

The optical and photovoltaic properties of a photovoltaic cell with a structure of indium–tin oxide (ITO)/double ZnO/poly(3-hexylthiophene) (PAT6):PCBM/Ag have been investigated. The double layer ZnO was a composite of a sputtered ZnO layer and oriented zinc oxide nanopillars layer which was fabricated by a new method at low temperature (343 K). It is concluded that the double layer ZnO plays an important role in collecting photogenerated electrons and acts as a conducting path to the electrode. Insertion of the double layer ZnO in the photovoltaic cells produced enhanced performance with the power conversion efficiency of 1.42% under AM1.5 illumination.     

基于石墨烯薄膜材料的肖特基结光伏器件研究进展

肖特基结太阳能电池因其结构简单、制备方便、成本低廉而受到广泛关注。石墨烯材料具有优异的物理性能以及原料来源丰富、制备成本低,可替代传统的ITO用于制备基于石墨烯的肖特基结太阳能电池。综述了现阶段基于石墨烯肖特基结太阳能电池的研究进展,探讨和分析了不同类型石墨烯肖特基结太阳能电池的性能以及在应用中存在的问题,为后续开展石墨烯肖特基结太阳能电池的研究与应用提供借鉴。     

Schottky solar cells based on colloidal nanocrystal films

We describe here a simple, all-inorganic metal/NC/metal sandwich photovoltaic (PV) cell that produces an exceptionally large short-circuit photocurrent (>21 mA cm(-2)) by way of a Schottky junction at the negative electrode. The PV cell consists of a PbSe NC film, deposited via layer-by-layer (LbL) dip coating that yields an EQE of 55-65% in the visible and up to 25% in the infrared region of the solar spectrum, with a spectrally corrected AM1.5G power conversion efficiency of 2.1%. This NC device produces one of the largest short-circuit currents of any nanostructured solar cell, without the need for sintering, superlattice order or separate phases for electron and hole transport.     

Enhanced efficiency of graphene-silicon Schottky junction solar cell through inverted pyramid arrays texturation

Nanostructures of silicon are gradually becoming hot candidate due to outstanding capability for trapping light and improving conversion efficiency of solar cell. In this paper, silicon nanowires (SiNWs) and silicon inverted pyramid arrays (SiIPs) were introduced on surface of Gr-Si solar cell through silver and copper-catalyzed chemical etching, respectively. The effects of SiNWs and SiIPs on carrier lifetime, optical properties and efficiency of Gr-SiNWs and Gr-SiIPs solar cells were systematically analyzed. The results show that the inverted pyramid arrays have more excellent ability for balancing antireflectance loss and surface area enlargement. The power conversion efficiency (PCE) and carrier lifetime of Gr-SiIPs devices respectively increase by 62% and 34% by comparing with that of Gr-SiNWs solar cells. Finally, the Gr-SiIPs cell with PCE of 5.63% was successfully achieved through nitric acid doping. This work proposes a new strategy to introduce the inverted pyramid arrays for improving the performance of Gr-Si solar cells.     

GaN nanorod Schottky and p-n junction diodes

Conductive atomic force microscopy has been used to characterize single GaN nanorod Schottky and p-n junction diodes. The ideality factor, reverse breakdown voltage, and the Schottky barrier height of individual nanorod diodes were compared to those from conventional thin-film diodes. Large-area contacts, enabling diodes with arrays of GaN nanorods in parallel, were also fabricated and their electrical characteristics investigated. The defect-free nature of the GaN nanorods and enhanced tunneling effects due to nanoscale contacts have been invoked to explain the electrical behavior of the nanorod diodes.     

Hot Wire CVD for thin film triple junction cells and for ultrafast deposition of the SiN passivation layer on polycrystalline Si solar cells

We present recent progress on hot-wire deposited thin film solar cells and applications of silicon nitride. The cell efficiency reached for μc-Si:H n-i-p solar cells on textured Ag/ZnO presently is 8.5%, in line with the state-of-the-art level for μc-Si:H n-i-p's for any method of deposition. Such cells, used in triple junction cells together with hot-wire deposited proto-Si:H and plasma-deposited SiGe:H, have reached 10.5% efficiency. The single junction μc-Si:H n-i-p cell is entirely stable under prolonged light soaking. The triple junction cell, including protocrystalline i-layers, is within 3% stable, due to the limited thicknesses of the two top cells. The application of SiN_x:H at a deposition rate of 3 nm/s to polycrystalline Si wafer solar cells has led to cells with 15.7% efficiency. We have also achieved record high deposition rates of 7.3 nm/s for transparent and dense SiN_x;H. Hot-wire SiN_x:H is likely to be the first large commercial application of the Hot Wire CVD (Cat-CVD) technology.     

Radial junction amorphous silicon solar cells on PECVD-grown silicon nanowires

Constructing radial junction hydrogenated amorphous silicon (a-Si:H) solar cells on top of silicon nanowires (SiNWs) represents a promising approach towards high performance and cost-effective thin film photovoltaics. We here develop an all-in?situ strategy to grow SiNWs, via a vapour-liquid-solid (VLS) mechanism on top of ZnO-coated glass substrate, in a plasma-enhanced chemical vapour deposition (PECVD) reactor. Controlling the distribution of indium catalyst drops allows us to tailor the as-grown SiNW arrays into suitable size and density, which in turn results in both a sufficient light trapping effect and a suitable arrangement allowing for conformal coverage of SiNWs by subsequent a-Si:H layers. We then demonstrate the fabrication of radial junction solar cells and carry on a parametric study designed to shed light on the absorption and quantum efficiency response, as functions of the intrinsic a-Si:H layer thickness and the density of SiNWs. These results lay a solid foundation for future structural optimization and performance ramp-up of the radial junction thin film a-Si:H photovoltaics.     

Optimized structure of AlGaAs/GaAs double junction solar cells

In this paper, the sub-layers of AlGaAs/GaAs double junction (DJ) solar cell have been redesigned in order to achieve an optimum cell structure. It has been deduced with cooperation of detailed balance limit theory and structural behaviour of AlGaAs, that the Al_0.45Ga_0.55As is the best choice for top cell’s material in AlGaAs/GaAs DJ solar cell. Also, there is a trade-off between peak tunnelling current and transparency in tunnel junction which makes Al_0.07Ga_0.93As as the optimum tunnel junction of AlGaAs/GaAs cell. Finally, a smoothed reflectance senary-layer structure based on modified-DBR has been proposed to be used as anti-reflection coating of proposed structure. Also, the thickness and doping concentration level of different layers have been optimized.     

氮化镓肖特基结紫外探测器的异常特性测量

测量了CaN肖特基结紫外探测器在有、无光照下的I-V异常特性。分别用362nm和368nm光束对有源区进行横向扫描,得到了光照不同部位时探测器在无偏压、2V反向偏压下的电流。紫外光照到肖特基结压焊电极附近及透明电极边沿附近区域时,探测器在反向偏压下有较大增益,空间响应均匀性变差,在禁带内有两个增益响应峰波长——364nm和368nm。探测器在810nm光照射下,反向偏压下的光响应增益、持续光电导存在光淬灭现象。探测器紫外光照完后,俘获中心及表面陷阱所俘获的部分电荷在高反向偏置电压下老化可以通过隧穿或发射效应释放出来,经过高反向偏置电压老化完后的探测器在同一低反向偏置电压下暗电流比老化前的要小。测量结果为GaN器件的研制提供了参考数据。     

染料敏化太阳能电池阻挡层的制备及其性能研究

采用电子束蒸发法在光阳极导电玻璃基底上制备了一层致密的TiO2薄膜,并在氧氛围下进行不同温度的退火处理。以此TiO2薄膜为阻挡层来阻止电解质溶液中I3-与导电玻璃基底上光生电子的复合。分别利用X射线衍射（XRD）和X射线光电子能谱（XPS）对此薄膜的结构和成分进行表征。制备不同厚度的TiO2阻挡层薄膜并研究其对电池光电性能的影响。实验结果表明,阻挡层的引入有效地抑制了暗反应的发生,提高了染料敏化太阳能电池（DSSC）的开路电压、短路电流和光电转换效率,比未引入阻挡层的DSSC的光电转换效率提高了31.5%。     

Polymer solar cells with a TiO2:Ag layer

Photovoltaic (PV) polymer solar cells with Ag and titanium dioxide were fabricated to improve the PV performance by increasing the amount of Ag in TiO₂ (by 3, 5, 7, and 10%). Sol–gel method was used to obtain amorphous or crystalline form of titanium dioxide layers. The solar cells with poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester active layer in two various positions of titanium dioxide in device were tested. Higher PV performance was received by introducing TiO₂ with 5% of Ag between ITO and PEDOT:PSS in device and by heating the layer at 130 °C. The viscosity of applied PEDOT:PSS strongly influences the values of power conversion efficiency of the constructed polymer devices with titanium dioxide.     

Stability of microcrystalline silicon solar cells with HWCVD buffer layer

Microcrystalline silicon solar cells deposited by VHF-PECVD with or without HWCVD grown p/i interface buffer layer were investigated. We studied long-term stability under storage in ambient atmosphere and performed light soaking experiments. Cells with i-layers covering a wide range of crystalline volume fractions were studied. All cells were stable or degraded slightly after storage for 2 years in air, regardless of crystalline volume fraction or presence of p/i buffer interface. Upon light soaking all cells show efficiency degradation to more or less extent depending on crystal volume fraction of the i-layer and the presence of the buffer layer: the solar cell with high crystal volume fraction are nearly stable, cells with high amorphous volume fraction degrade by up to 20%. The solar cell with HWCVD buffer layer shows better stability in the high efficiency range of relative efficiency degradation typically less than 10% after 1000 h AM 1.5 light soaking. The efficiency degradation is mainly caused by Voc and FF deterioration while Jsc is almost stable.     

Novel fabrication of copper nanowire/cuprous oxidebased semiconductor-liquid junction solar cells

Nano Research - A Cu nanowire (NW)/cuprous oxide (Cu2O)-based semiconductor-liquid junction solar cell with a greatly enhanced efficiency and reduced cost was assembled. The Cu NWs function as a...