Comparative study of Cu2ZnSnSe4 solar cells growth on transparent conductive oxides and molybdenum substrates

International audienceCu 2 ZnSnSe 4 (CZTSe) thin films have been synthetized by cosputtering followed by a selenization treatment on Mo and transparent conductive oxide (TCO) coated soda lime glass substrates, such as ZnO:Al and SnO 2 :F (FTO). The aims of the present work is to investigate the impact of the TCO substrates on the CZTSe growth, the reactions at the back contact and the electrical properties of solar cells. The results show that the morphology of CZTSe is affected by the TCO back contacts. It is found that TCO acts as a diffusion barrier of Na from soda lime glass to CZTSe. Thus low incorporation of Na during the annealing could explain the difference in grain size of CZTSe deposited on TCO. Moreover it is evidenced chemical reactions between TCO and CZTSe which affects the interface. While the efficiency up to 8% is obtained for CZTSe based solar cells deposited on Mo substrate, the efficiency drops to 2.3% for the solar cells deposited on FTO. The low efficiency is explained by the recombination at the back contact due to the formation of the ZnO secondary phase at the CZTSe/FTO interface

Chemical crystallographic investigation on Cu2S-In2S3-Ga2S3 ternary system

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Use of shelter by grazing bulls: effect of climatic factors

The time spent under a shelter by eight grazing fattening bulls of the Belgian Blue breed in each of 3 years consecutively for a total of 48 days was recorded using a time-lapse recorder with infrared illumination. During one grazing period, data were collected over 35 days (experiment 1). Observations were divided into 166 h with rain (20%) and 674 h without precipitation (80%). The average occupation rates were 15.4 (s.e. 29.1)% for the hours with rain and 4.5 (s.e. 14.8)% for the hours without precipitation (P < 0.001). The effect of intensity and duration of rain on the occupation rate was significant from 0.4 l/m(2) or from 2 h. Experiment 2 (13 days of observation) examined the influence of temperature and solar radiation on the use of shelter. The occupation rates were 21 (s.e. 23)% during the daylight hours (07.00 to 19.00 h), 6 (s.e. 8)% during the night (19.00 to 07.00 h) and 14 (s.e. 14)% during a 24-h period. The occupation rate between 07.00 and 19.00 h was significantly correlated to the mean daily temperature (r = 0.75), the maximum daily temperature (r = 0.86) and the direct solar radiation time (r = 0.60). When the maximum daily temperature exceeded 20 degrees C, the use of the shelter increased from 10 to 49% of the daylight hours. There was no significant difference between the live-weight gains of animals from the observed group and those of other bulls on an adjacent pasture without shelter. Nevertheless, these observations suggest that a shelter may improve the welfare of grazing cattle

Iterative method for optical modelling of perovskite-based tandem solar cells

International audienceWe present an iterative method to model the optical properties of a complete semitransparent perovskite solar cell. It is based on spectroscopic characterizations and accounts for porosity and incoherence effects. We provide the complex refractive indices of each layer, and we identify the main sources of optical losses. The optical model is also coupled to an electrical model of 4T perovskite/silicon tandem solar cells. It allows to evaluate the interplay between the optical and electrical losses, and the balance between the efficiency of the top and bottom cells. These models provide an effective way to design future tandem devices

CaCu3Ti4O12 Thin Films on Conductive Oxide Electrode: A Comparative Study between Chemical and Physical Vapor Deposition Routes

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