Preparation and Characterization of CdTe for Solar Cells, Detectors, and Related Thin-Film Materials

Abstract

Cadmium telluride (CdTe) thin films were prepared by the close-space sublimation (CSS) technique, using 99.99% pure CdTe powder as the evaporant. Films were then annealed at 400°C for 30 min and were later dipped in Cu(NO 3 ) 2 -H 2 O solution at 80 ± 2°C. After immersion these films were again annealed at 400°C for 1 h to ensure the Cu diffusion into the films. X-ray diffraction (XRD) results confirmed the formation of a new compound copper telluride and a change in the morphology was observed by scanning electron microscopy (SEM). The DC electrical resistivity reduced from 10 6 X-cm for as-deposited to 10 -3 X-cm for 15 h immersed film. As the wt.% of Cu increased, the mobility increased to some extent, while the carrier concentration showed a systematic increase. The film thickness and optical parameter such as refractive index, absorption coefficient, and the optical band gap were deduced by fitting the optical transmittance in the wavelength range 300 to 3000 nm. The transmission decreased with increasing immersion time of films in the solution. The Cu concentration was recorded as 0.9 wt.% for 3 min to 56.6 wt.% for 15 h immersed samples using an electron microprobe analyzer (EMPA). In the next step, ITO/CdS/CdTe heterojunctions with 10.9% solar cell efficiency were fabricated on glass slides.

Effects of CdCl2 Treatment on Physical Properties of CdTe/CdS Thin Film Solar Cell

“…The process will be followed according to the requirements and economic conditions. There are some major techniques used for thin film fabrication such as physical vapor deposition (PVD), closed space sublimation (CSS), chemical vapor deposition (CVD), chemical bath deposition (CBD), pulsed laser deposition (PLD), electro-deposition (ED), sputtering technique, and atomic layer epitaxy (ALE) [16][17][18]. So many techniques can be used for the CdTe.…”

“…The quality of thin films, material transport and deposition rate depends upon the fabrication parameters [17,18].…”

“…CdS (CBD) thin films are grown by cadmium chloride, ammonium nitrate, and potassium hydroxide. After heating to a specific temperature, thiourea is added to start the fabrication process [18][19][20]. CBD is very easy process for the fabrication of CdS thin films on ITO glass.…”

“…Hence, a variety of methods have been applied for the synthesis of such materials, e.g., thermal evaporation [16], chemical pyrolysis deposition (CPD) [17], metal organic chemical-vapor deposition (MOCVD) [18][19][20], closed space sublimation (CSS) [21] and chemical bath deposition (CBD) [22][23][24][25]. CSS and CBD are known to produce optimal and encouraging results for CdTe/CdS based solar cells.…”

Structural and optical properties of Cu-doped CdTe films with hexagonal phase grown by pulsed laser deposition

“…Because the stable phase of CdS is the hexagonal phase is very important to obtain CdTe in hexagonal phase. CdTe polycrystalline films can be prepared by several growth techniques such as closespace sublimation (CSS), 4 chemical deposition, 5 sputtering, 6 pulsed laser deposition (PLD), 7 vapor transport deposition (VTD), physical vapor deposition (PVD), spray deposition 1 among others. Some of these techniques, such as CSS, VTD, PVD requires a high growth temperature.…”