Liangxing Jiang

Enhancing the Cu2ZnSnS4 solar cell efficiency by back contact modification: Inserting a thin TiB2 intermediate layer at Cu2ZnSnS4/Mo interface

In this work, TiB2 thin films have been employed as intermediate layer between absorber and back contact in Cu2ZnSnS4 (CZTS) thin film solar cells for interface optimization. It is found that the TiB2 intermediate layer can significantly inhibit the formation of MoS2 layer at absorber/back contact interface region, greatly reduces the series resistance and thereby increases the device efficiency by short current density (Jsc) and fill factor boost. However, introducing TiB2 degrades the crystal quality of absorber, which is detrimental to device performance especially Voc. The careful control of the thickness of TiB2 intermediate layer is required to ensure both MoS2 with minimal thickness and CZTS absorber with large grain microstructure according to the absorber growth process.

Effects of potassium doping on solution processed kesterite Cu2ZnSnS4 thin film solar cells

Alkaline metals doping is one of the approaches for achieving high efficiency Cu(In,Ga)Se2 (CIGS) solar cell. Recently, potassium doping helps to break the record efficiency of CIGS solar cell doped with sodium. In this paper, we have investigated how incorporation of potassium can influence the properties of Cu2ZnSnS4 (CZTS) thin film and the performance of resulting solar cell. Our results showed that K doping can enhance the (112) preferred orientation, increase the grain size and reduce the second phase ZnS of the CZTS thin films. After K doping, despite of some drop of Voc for CZTS thin film solar cells, the Rs is decreased and the Jsc is improved markedly, and the solar cell efficiency is boosted.

Kesterite Cu2ZnSn(S,Se)4 Solar Cells with beyond 8% Efficiency by a Sol–Gel and Selenization Process

A facile sol-gel and selenization process has been demonstrated to fabricate high-quality single-phase earth abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic absorbers. The structure and band gap of the fabricated CZTSSe can be readily tuned by varying the [S]/([S] + [Se]) ratios via selenization condition control. The effects of [S]/([S] + [Se]) ratio on device performance have been presented. The best device shows 8.25% total area efficiency without antireflection coating. Low fill factor is the main limitation for the current device efficiency compared to record efficiency device due to high series resistance and interface recombination. By improving film uniformity, eliminating voids, and reducing the Mo(S,Se)2 interfacial layer, a further boost of the device efficiency is expected, enabling the proposed process for fabricating one of the most promising candidates for kesterite solar cells.

Efficient Planar Perovskite Solar Cells with Reduced Hysteresis and Enhanced Open Circuit Voltage by Using PW12–TiO2 as Electron Transport Layer

An electron transport layer is essential for effective operation of planar perovskite solar cells. In this Article, PW12-TiO2 composite was used as the electron transport layer for the planar perovskite solar cell in the device structure of fluorine-doped tin oxide (FTO)-glass/PW12-TiO2/perovskite/spiro-OMeTAD/Au. A proper downward shift of the conduction band minimum (CBM) enhanced electron extraction from the perovskite layer to the PW12-TiO2 composite layer. Consequently, the common hysteresis effect in TiO2-based planar perovskite solar cells was significantly reduced and the open circuit voltage was greatly increased to about 1.1 V. Perovskite solar cells using the PW12-TiO2 compact layer showed an efficiency of 15.45%. This work can contribute to the studies on the electron transport layer and interface engineering for the further development of perovskite solar cells.

Electroabsorption measurements and built-in potentials in amorphous silicon {ital p}{endash}{ital i}{endash}{ital n} solar cells

We present a technique for using modulated electroabsorption measurements to determine the built‐in potential in semiconductor heterojunction devices. The technique exploits a simple relationship between the second‐harmonic electroabsorption signal and the capacitance of such devices. We apply this technique to hydrogenated amorphous silicon (a‐Si:H)‐based solar cells incorporating microcrystalline Si p+ layers. For one set of cells with a conventional plasma‐deposited intrinsic (i) layer we obtain a built‐in potential of 0.98±0.04 V; for cells with an i layer deposited using strong hydrogen dilution we obtain 1.25±0.04 V. We speculate that interface dipoles between the p+ and i layers significantly influence the built‐in potential.

Colloidal synthesis and characterisation of Cu3SbSe3 nanocrystals

Cu3SbSe3 nanocrystals have been synthesized using a hot-injection method. The Cu3SbSe3 nanocrystals possess a band gap of 1.31 eV and the corresponding nanocrystal-electrode shows an incident photon to current efficiency (IPCE) of 10–35% in the visible region. Our work demonstrates that Cu3SbSe3 nanocrystals have potential in photo-electric conversion device applications.

Novel phosphorus-doped PbO2–MnO2 bicontinuous electrodes for oxygen evolution reaction

We report a facile electrochemical approach for the fabrication of phosphorus-doped (P-doped) PbO2–MnO2 composite electrodes with a microporous bicontinuous structure. Modification of such structures was achieved by controlling the MnO2 incorporation during an anodic co-deposition process. The results indicate the anodic co-oxidation of Pb2+ and Mn2+ yielded a P–(PbO2–MnO2) deposit with a flat, compact and smooth surface. Meanwhile, the anodic composite deposition of Pb2+ and MnO2 particles resulted in the bicontinuous (P–PbO2)–MnO2 composite with a well-defined microporous morphology. Tafel and EIS were used to characterize their electrocatalytic performances for the oxygen evolution reaction in a typical anodic water-splitting process. The results indicate that such a novel bicontinuous (P–PbO2)–MnO2 composite anode exhibits significantly improved electrocatalytic activity as compared to the P–PbO2 and P–(PbO2–MnO2) anodes. The oxygen evolution kinetics and possible reaction mechanism are further described.

Flexible Cu2ZnSnS4 solar cells based on successive ionic layer adsorption and reaction method

Using a commercially viable and environmentally friendly aqueous chemical method, Cu2ZnSnS4 films with different stacked structure precursors are prepared on flexible Mo foil substrates, and then solar cells with the structure of Ag/AZO/i-ZnO/CdS/CZTS/Mo foil are fabricated. A comparative study reveals that the absorber from the Cu2SnSx/ZnS/Mo precursor shows preferable crystallinity and morphology than that from ZnS/Cu2SnSx/Mo precursor. Accordingly, the device based on the former absorber yields better performance, demonstrating an efficiency of 2.42%. Issues involved microstructure and secondary phases that limit the performance of the device are discussed.

Hydrogen evolution inhibition with diethylenetriamine modification of activated carbon for a lead-acid battery

A novel idea to inhibit the hydrogen evolution in activated carbon (AC) application in a lead-acid battery has been presented in this paper. Nitrogen group-enriched AC (NAC, mainly exists as pyrrole N) was prepared. Electrochemical measurements demonstrate that the hydrogen evolution reaction (HER) is markedly inhibited as the HER impedance increases significantly. Whats more, the specific capacitance value of NAC is 142.5% higher than AC since the working window is extended. The use of NAC, instead of AC in an UltraBattery, can inhibit hydrogen evolution, and improve the batterys charge acceptance and charge retention ability.

Photoelectrochemically deposited Sb2Se3 thin films: deposition mechanism and characterization

Sb2Se3 thin films were photoelectrochemically deposited (PED) and displayed a compelling photoelectrochemical (PEC) performance. The main influence of the illumination mechanism on Sb2Se3 deposition is that the photoconductive effect accelerates the deposition rate and the photogenerated electrons (in the conduction band of the deposited Sb2Se3 thin film) promote the electroreduction of SbO+. Electrochemical impedance spectroscopy (EIS) and potentiostatic polarization show evidence that illumination can promote the rate of cathodic reduction. Linear sweep photovoltammetry (LSPV) and X-ray fluorescence spectrometry (XRF) indicate that illumination facilitates the reduction of SbO+. The PED process can improve the homogeneity and compactness of the films, facilitate the growth of stoichiometric Sb2Se3 and further enhance the photocurrent response of films, compared to the conventional electrochemical deposition (CED) process.