Sodium induced grain growth, defect passivation and enhancement in the photovoltaic properties of Cu2ZnSnS4 thin film solar cell

Sodium diffusion from soda lime glass (SLG) during high temperature annealing is known to play a crucial role in affecting the grain growth and defect passivation in chalocogenide/kesterite solar cells. Additional sodium is required when low temperature or short term annealing is used. Although this fact is known, a systematic comparative study for kesterite films is seldom reported. In the present study, Cu2ZnSnS4 thin films were deposited on SLG and Mo coated SLG using stacked layer reactive sputtering. Na was deposited over the CZTS thin film and the film was annealed in N-2 atmosphere in order to enhance the grain growth. This resulted in the shift in the XRD peak towards lower diffraction angle. The optical bandgap shifted from 1.45 eV to 1.38 eV with Na addition. Significant grain growth from hundreds of nanometer to micrometer was observed in samples with Na. Device fabricated in SLG/Mo/CZTS/CdS/ZnO/ITO configuration with Al front contact shows increase in efficiencies values from 1.50% to 2.84%

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Highly responsive, low -bias operated SnSe 2 nanostructured thin film for trap -assisted NIR photodetector

Photo detectors are very important for operation of various opto-electronic devices, like night vision camera, thermal imaging, remote sensing and so on. As the sizes of devices are shrinking day by day, it is important to make photo detectors which are small, robust, stable and have good responsitivity. Also the materials should be made from earth abundant elements and can be deposited using simple deposition techniques. Recently, good photo-detection capabilities in the infrared as well as visible range have been reported in metal dichalcogenides (WSe2; MoSe2; SnSe2; SnS2;WS2; MoS2; PtSe2; PdSe2 etc). SnSe2 is made of earth abundant elements. In this study, we report IR photo response in SnSe2 nanostructured thin films grown on soda lime glass (SLG) by thermal evaporation technique. IR (1064 nm) photo response behavior of the film is measured at different bias voltages in 100e400 mV range in steps of 100 mV and laser power density of 30e79 mW=cm2. The responsitivity of the device shows non-saturation of the traps states in the device. The value of responsitivity was 0.796± 0.003 mA/W (standard deviation) at 79 mW= cm2 laser power density and 400 mV bias voltage and the rise/decay times were 276 ms/332 ms, respectively. It is to be noted that the photo response behavior of film was stable and reproducible even after keeping them in atmospheric conditions for many months. This shows the potential of SnSe2 as a suitable material for various opto-electronic applications. To the best of our knowledge, the present study shows superior values of responstivity and response/recovery time of SnSe2 thin film on SLG substrate

High-speed, low-bias operated, broadband (Vis-NIR) photodetector based on sputtered Cu2ZnSn(S, Se)(4) (CZTSSe) thin films

Photodetectors have large applications in the current ongoing pandemic. These can be used to study the growth of viruses where depending upon the concentration the light intensity will be reduced. Since the viruses grow very fast therefore a device with very low response time as well as quick recovery will be useful for this study. If the device can be made from the non-toxic materials and sizes are quite small, they can be used for in vitro studies as well. Kesterite Cu2ZnSn(5, Se)(4) (CZTSSe) thin film can be deposited over flexible substrates. The detectivity of even very small area device is very high with ultra-small response and recovery time. The CZTSSe PD exhibited excellent broadband (Vis-NIR) photoresponse, high responsivity of 18.0 mA.W-1, a fast rise time of 82 ms, and a decay time of 97 ms, as well as high detectivity (similar to 10(9) Jones) with favorable self-powered characteristics. This work suggests significant scientific insights for photoconductivity properties of emerging kesterite CZTSSe thin-film materials for broadband, low-cost, high-efficiency next-generation thin-film photodetectors for various optoelectronic applications including diagnostic