Flexible CZTSSe Thin-Film Solar Cells with Over 14% Certified Efficiency Enabled by Lithium Doping

Flexible CZTSSe thin film solar cells fabricated at low temperature with relieved residual stress by Sb incorporation

Vapor textured aluminum-doped zinc oxide on cellophane paper for flexible thin film solar cells

Flexible thin-film solar cell is an efficient energy system on the surface of stratospheric airship for utilizing the solar energy. In order to ensure the normal operation of airship platform, the thermal control problem between the flexible thin-film solar cell and the airship envelope should be properly resolved. In this paper, a multilayer insulation material (MLI) is developed first, and low temperature environment test is carried out to verify the insulation effect of MLI. Then, a thermal heat transfer model of flexible thin-film solar cell and MLI is proposed, and the equivalent thermal conductivity coefficients of flexible thin-film solar cell and Nomex honeycomb are calculated based on the environment test and the temperature profile of flexible thin-film solar cell versus each layer of MLI. Finally, FLUENT is used for modeling and simulation analysis on the flexible thin-film solar cell and MLI, and the simulation results agree well with the experimental data, which validate the correctness of the proposed heat transfer model of MLI. In some way, our study can provide helpful support for further engineering applications of flexible thin-film solar cell.

We present the application of ultraviolet (UV) nanoimprint lithography for the replication of advanced light management schemes in flexible thin-film solar cells. The approach is maintained entirely at low temperatures, which are required for the development of flexible solar cells on low-cost transparent polymer films. Light-scattering properties are significantly improved by this technique, and thin-film silicon solar cells prepared on these substrates show a substantial improvement in performance due to the nanoimprinted texture. We further investigate the effect of various incident angles of the light on the short-circuit current density (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> ) of the solar cell and evaluate the corresponding performance of a flexible solar cell in a bent state. Our results show that in the case of imprinted texture, the J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> and efficiency is reduced within 5% in a bent case of a semicircle when a reduction of the effective illumination area with angle is not taken into account. Overall, the solar cell on imprint-textured polyethylene terephthalate (PET) film shows an increased J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">sc</sub> for the entire range of incident angles and bent states compared with the nonimprinted PET substrate.

Effect of evaporated CdS layer on formation and performance enhancement of flexible Cu2ZnSn(S,Se)4 solar cells

The electrical property at the grain boundaries (GBs) of Cu2ZnSn(S,Se)4 (CZTSSe) thin film is very important to fabricate a high efficiency device and it is closely interrelated with alkali elements. Here, we used Kelvin probe force microscopy to confirm that spike-type contact potential difference formed at the GBs in CZTSSe thin film after potassium (K) doping, which could attract the electrons to travel through the grains boundaries and was favorable for obtaining a device with better performance. K also could promote the grain growth of CZTSSe thin films. With the help of K doping, a flexible CZTSSe solar cell with an efficiency over 3% was obtained.

Performance improvement of flexible CZTSSe thin film solar cell by adding a Ge buffer layer

Synthesis of ITO nanoparticles at room temperature using plasma treatment process and use it as back reflector in a-Si flexible solar cell

Changes in surface morphology and roughness of dc sputtered ZnO:Al/Ag back reflectors by varying the deposition temperature and their influence on the performance of flexible silicon thin film solar cells were systematically investigated. By increasing the deposition temperature from <TEX>$25^{\circ}C$</TEX> to <TEX>$500^{\circ}C$</TEX>, the grain size of Ag thin films increased from 100 nm to 1000 nm and the grain size distribution became irregular, which resulted in an increment of surface roughness from 6.6 nm to 46.6 nm. Even after the 100 nm thick ZnO:Al film deposition, the surface morphology and roughness of the ZnO:Al/Ag double structured back reflectors were the same as those of the Ag layers, meaning that the ZnO:Al films were deposited conformally on the Ag films without unnecessary changes in the surfacefeatures. The diffused reflectance of the back reflectors improved significantly with the increasing grain size and surface roughness of the Ag films, and in particular, an enhanced diffused reflectance in the long wavelength over 800 nm was observed in the Ag back reflectors deposited at <TEX>$500^{\circ}C$</TEX>, which had an irregular grain size distribution of 200-1000 nm and large surface roughness. The improved light scattering properties on the rough ZnO:Al/Ag back reflector surfaces led to an increase of light trapping in the solar cells, and this resulted in a noticeable improvement in the <TEX>$J_{sc}$</TEX> values from 9.94 mA/<TEX>$cm^2$</TEX> for the flat Ag back reflector at <TEX>$25^{\circ}C$</TEX> to 13.36 mA/<TEX>$cm^2$</TEX> for the rough one at <TEX>$500^{\circ}C$</TEX>. A conversion efficiency of 7.60% (<TEX>$V_{oc}$</TEX> = 0.93, <TEX>$J_{sc}$</TEX> = 13.36 mA/<TEX>$cm^2$</TEX>, FF = 61%) was achieved in the flexible silicon thin film solar cells at this moment.

In this work, an intermediate layer of Mo is pre‐deposited on the flexible Mo foil before the deposition of Cu2ZnSnS4 (CZTS) thin film to optimise the characteristics of the flexible CZTS thin film solar cell (TFSC). It is confirmed that the pre‐deposition of the Mo layer leads to the improvement in the degree of the interface matching between the back electrode and the CZTS thin film which is always regarded as the main recombination centres of the carriers in the solar cell. By employing a Mo interlayer between the Mo foil and CZTS layer, the conversion efficiency of the as‐fabricated (Mo foil/Mo/CZTS/CdS/i‐ZnO/AZO/Ni/Al) solar cell is further increased from 1.27 to 1.46%. Meanwhile, the traditional structure (soda‐lime glass/Mo/CZTS/CdS/i‐ZnO/AZO/Ni/Al) CZTS TFSC acted as a matched group which is also prepared and obtained a conversion efficiency of 1.58%. This work demonstrates for the first time the effects of Mo intermediate layers in the flexible CZTS TFSCs.

Controlled substitution of S by Se in reactively sputtered CZTSSe thin films for solar cells

A real-time solar cell based in vivo dosimetry system (SC-IVD) was developed using a flexible thin film solar cell and scintillating powder. The present study evaluated the clinical feasibility of the SC-IVD in electron beam therapy. A thin film solar cell was coated with 100 mg of scintillating powder using an optical adhesive to enhance the sensitivity of the SC-IVD. Calibration factors were obtained by dividing the dose, measured at a reference depth for 6-20 MeV electron beam energy, by the signal obtained using the SC-IVD. Dosimetric characteristics of SC-IVDs containing variable quantities of scintillating powder (0-500 mg) were evaluated, including energy, dose rate, and beam angle dependencies, as well as dose linearity. To determine the extent to which the SC-IVD affected the dose to the medium, doses at R90 were compared depending on whether the SC-IVD was on the surface. Finally, the accuracy of surface doses measured using the SC-IVD was evaluated by comparison with surface doses measured using a Markus chamber. Charge measured using the SC-IVD increased linearly with dose and was within 1% of the average signal according to the dose rate. The signal generated by the SC-IVD increased as the beam angle increased. The presence of the SC-IVD on the surface of a phantom resulted in a 0.5%-2.2% reduction in dose at R90 for 6-20 MeV electron beams compared with the bare phantom. Surface doses measured using the SC-IVD system and Markus chamber differed by less than 5%. The dosimetric characteristics of the SC-IVD were evaluated in this study. The results showed that it accurately measured the surface dose without a significant difference of dose in the medium when compared with the Markus chamber. The flexibility of the SC-IVD allows it to be attached to a patient's skin, enabling real-time and cost-effective measurement.

Development of textured back reflector for n–i–p flexible silicon thin film solar cells

Effect of evaporated Sb layer on performance of flexible CZTSSe thin film solar cell

The inhibition of the rapid recombination of photochemical charges at heterointerfaces and the promotion of transfer and extraction are central to photoelectric conversion in solar cells. With the use of Cu4Bi4S9 nanoribbons-graphene sheets (CBS-GSs) as a hybrid photosensitive layer and the growth of ZnO nanowires on Zn2SnO4 nanowires (ZTO-ZnO) for the electron transfer layer, a flexible solar cell ZTO-ZnO/CBS-GSs was prepared on a stainless steel mesh. In this study, time-resolved fluorescence spectroscopy (TFS) and transient surface photovoltage (TPV) were used to describe the transition and transport process for the photogenerated carriers. With a high fill factor (0.76) and improved electron mobility for the ZTO-ZnO nanostructure, a high photoelectric conversion efficiency of 11.6% was obtained, which was evidently higher than that of a ZTO/CBS-GSs cell (9.2%) and a ZnO nanoparticles/CBS-GSs cell (3.9%). The efficient dissociation of photogenerated carriers at CBS-GSs interfaces, rapid transfer of free electrons in the ZTO-ZnO system, and fast extraction of holes from the selective NiO layer with an optimized architecture led to a superior performance. The charge recombination at the interface can be determined by electrochemical impedance spectroscopy (EIS). Active exploration via inevitable competition between charge separation and recombination (TFS, TPV, EIS, etc.) can provide insights into the entire dynamic process and a separation mechanism for photoinduced carriers, which can also promote the application of flexible thin-film solar cells.