Search

Solar cells based on perovskite absorbers are rapidly emerging as attractive candidates for photovoltaics development. Understanding the role of the electron-transport layer (ETL) is very important to obtain highly efficient perovskite solar cells. Herein, the effect of the ETL on device performance in planar perovskite solar cells is investigated in detail, and the band bending in different situations is discussed. The ET barrier is shown to be responsible for the poor fill factor (FF) of J-V curves. Introduction of a thin bathocuproine interlayer increases the interface inversion and results in an increase of FF from 56 to 76 %. Some experimental and theoretical results verify these conclusions. Furthermore, this study can provide an interface-engineering strategy to improve device performance.

Organic–inorganic halide perovskites possess excellent chemical, optical, and electronic properties that make them attractive for next-generation solar cells. An important target for the further improvement of perovskite-based solar cells is to eliminate or reduce the use of the heavy metal lead. Herein, we systematically investigated the performance of FAPb1−xSnxI3 mixed metal halide perovskites. The addition of Sn led to the stabilization of the perovskite phase and the low temperature of 100 °C was enough to result in the formation of the perovskite phase. The efficiency of the solar cell fabricated in this study is over 10% at x = 0.5, owing to the improved light harvesting in spite of the reduced open voltage. As more Sn was added, the device performance gradually deteriorated. Importantly, we performed stability tests under white light illumination and demonstrated that the FASn0.5Pb0.5I3 material might be intrinsically stable in a nitrogen environment. These results show that the device based on the FASn0.5Pb0.5I3 absorber without encapsulation retained over 85% of the initial efficiency for 100 h in nitrogen, indicating that a highly efficient perovskite solar cell with reduced Pb content and long-term stability could be realized.

Methylammoniumn lead iodide perovskites have attracted great attention in photovoltaic research community. In this work, we demonstrate the results of studies focusing on the chemical reaction of CH3NH3PbI3-xClx layer formation during the annealing of perovskite precursor films. We identified two kinds of grain morphologies during the formation of perovskite films grown from non-stoichiometric precursor solution. To form single-phase and high absorbance perovskite films, higher concentration of chloride in precursor solution needs longer annealing time and only a very low Cl content could be incorporated in the final CH3NH3PbI3-xClx films. Adding PbCl2–3CH3NH3I to PbI2–CH3NH3I precursor solution can allow a good control of the growth rate and morphology for the final perovskite film, and is beneficial to the photovoltaic performance of perovskite devices. By employing the precursor solutions of PbCl2, PbI2 and CH3NH3I with a mole ratio of 1:1:4 and inserting an ultrathin amino-functionalized polymer interlayer, we achieved planar perovskite solar cell with maximum power conversion efficiency of over 15%.

Organic–inorganic halide perovskites possess excellent chemical, optical, and electronic properties that make them attractive for next-generation solar cells. In this paper, we introduce all-low-temperature processed perovskite solar cells using metal sulfide as an electron transport layer. First, we evaluated the alignment of energy levels at the perovskite/metal sulfide layer interface. The properties of metal sulfide and the perovskite layer, as well as the corresponding device performance, were then investigated. Using a CdS layer as an electron transport layer, we have achieved a maximum power conversion efficiency of 11.2% under reverse scans. The successful use of the CdS layer in perovskite solar cells likely would create new pathways and opportunities for the advancement of device design.

Organic–inorganic hybrid perovskites were prepared by thermal evaporation from precursor materials PbCl2 and CH3NH3I (MAI). The structures of the perovskite films with various ingredients were characterized by X-ray diffraction (XRD), UV-vis absorption, and scanning electron microscopy (SEM). We found that with the addition of MAI material the evaporated PbCl2 films were initially transformed to PbI2, then to standard a stoichiometric perovskite and finally to the MAPbI3·xMAI phase. The film composition ingredients strongly affect the device performance. An unmatched PbCl2 to MAI ratio in the evaporated films resulted in reduced conversion efficiency and higher moisture sensitivity. The planar perovskite solar cells with organic charge layers showed negligible photocurrent hysteresis and delivered a power conversion efficiency of 10.5%.

Flexible Cu2ZnSnS4 (CZTS) solar cell absorbers were prepared by sulfurizing Cu–Zn–Sn precursors which were co-electrodeposited on Mo-coated molybdenum foil in a one-step process. A photovoltaic device with 3.82% conversion efficiency based on the illumination area of 0.35 cm2 was attained, which is the first efficiency report of flexible CZTS-based solar cells on molybdenum foil.

This work is the first report of using a deep eutectic solvent named Reline as a green electrolyte to electrodeposit CZTS films for photovoltaic applications. This is successfully achieved by co-electrodepositing Cu–Zn–Sn precursor thin films in Reline and sulfurizing the Cu–Zn–Sn precursors in a mixture of H2S and N2 at 550 °C for 1 h. The CZTS films are uniform and compact on a microscopic scale, which translates to a benign photoresponse of the CZTS solar cell. Photovoltaic devices were prepared from the films and an efficiency of 3.87% has been achieved. The device performance indicates that Reline is a viable green solvent for the electrodeposition of CZTS thin film solar cells in a low cost way.

Organic–inorganic halide perovskite-based thin film solar cells show excellent light-to-power conversion efficiency. The high performance for the devices requires the preparation of well-crystallized perovskite absorbers. In this paper, we used the postannealing process to treat the perovskite films under different solvent vapors and observed that the solvent vapors have a strong effect on the film growth. A model regarding the perovskite film growth was proposed as well. Intensive characterizations including scanning electron microscopy, electrochemical impedance spectroscopy, and admittance spectroscopy allowed us to attribute the improved performance to reduced recombination loss and defect density. Solar cell based on the DMSO-treated films delivered a power conversion efficiency of over 13% with negligible photocurrent hysteresis.

In this paper, CdTe solar cells of ~10% efficiency with a structure of anti-radiation glass/ITO/ZnO/CdS/CdTe/ ZnTe/ZnTe:Cu/Au were irradiated by 1.7 MeV irradiation with various fluences. Testing methods, such as light and dark IV, quantum efficiency, admittance spectroscopy were used to study the performances of CdTe cells before and after irradiation. Comprehensive electron irradiation damage effect on the characteristics and physical mechanism of charge transport were analyzed. The results show that the main junction CdS/CdTe is easy being destroyed and there are two defects induced by high energy electron irradiation, whose positions in the forbidden band are close to 0.46±0.05 eV and 0.44±0.04 eV above the valence band, and capture cross sections are 1.32×10-15 cm2 and 3.09×10-15 cm2, respectively, and under different irradiation fluences, the quantum efficiency of the solar cells decreases, especially in 550nm-800nm. As a result, the short circuit current decreases after irradiation.

Successful numerical simulations can reveal important flow characteristics and information which are extremely difficult to obtain by experiment. Two-dimensional numerical simulation of drag coefficients on two square cylinders at high Reynolds number (Re=4×106) are performed in this paper. At first the drag coefficient of single square cylinder is achieved. The drag coefficients and corresponding cover flow influence coefficients are calculated when the spacing ratios are set at 1, 2, 3, 4, 6, 8, 12, 16 and 20 when two square cylinders arranged in-line. In the two parallel square cylinders case, the drag coefficients and transverse influence coefficients are calculated when the spacing ratios are set at 2, 4, 6, 8, 12 and 15. The relationship between drag coefficient and spacing ratio in different cylinder layout are summarized.

The ZnO high resistivity transparent (HRT) layers were prepared by DC magnetron sputtering on the 1 mm borosilicate glass with 150 nm ITO coating. The structural, optical and electrical properties of the as-deposited films were investigated by XRD, UV/Vis spectroscopy and four-probe technology. The interface characters of the ITO/ZnO and ZnO/CdS systems were studied by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) depth profiling tests. The results show that ZnO has good optical and electrical properties. The insertion of the ZnO films decreases the energy barrier between ITO and CdS films. The energy conversion efficiency and quantum efficiency were found to be 12.77% (8.9%) and > 90% (79%) with or (without) ZnO films of CdTe solar cells. Furthermore, the effect of thickness, mobility and carrier density of ZnO films on CdTe solar cells was analyzed by AMPD-1D.