Close‐Spaced Sublimation (CSS): A Low‐Cost, High‐Yield Deposition System for Cadmium Telluride (CdTe) Thin Film Solar Cells

Abstract

Semiconductors are the key materials in many of our modern day devices, such as sensors, integrated circuits, energy harvesting devices, optoelectronics and so on. However, apart from two known elemental semiconductors that are silicon and germanium, we have been using many of the synthesized ones since the microelectronic revolution known as invention of transistor. Numerous compound semiconductors since then have been synthesized, grown, deposited or simply fabricated by numerous processes in the scientific community. To avoid associated chemical disposals or keep safe from toxic or combustible gas usages in any semiconductor fabrication facilities, many researchers choose physical vapor deposition as the simplest method. One of such processes is called Close-Spaced Sublimation (CSS), which is a kind of thermal evaporation by nature. This chapter would give a comprehensive outline on CSS as one of the most advantageous semiconductor deposition processes for many compound semiconductors having relatively low evaporation temperature. Cadmium telluride (CdTe) is one of the examples utilized for solar cell absorber materials since the early 1980s using CSS technique. Therefore, growth of CdTe thin films by CSS and its utilization in thin film solar cells will be discussed to comprehend the ultimate benefits of the close-spaced sublimation (CSS) process.

Impact of CdCl2 Treatment in CdTe Thin Film Grown on Ultra-Thin Glass Substrate via Close Spaced Sublimation

“…This suggests an incomplete treatment process in specific temperatures (below 390 °C) and over-heating when annealing temperatures >410 °C applied. Since, in the CSS deposition process, films go through a transition temperature (600 °C) and experience the highest possible grain nucleation stage, the thickness will not increase significantly during treatment [44,45]. From Figure 5.…”

Wide Bandgap Sb2S3 Solar Cells

“…On the one hand, higher and controlled growth temperature improves the deposition rate; it also determines the superiority of junction quality. [96] CSS technique is very well known for the deposition of CdTe deposition for decades [97] and has also been successfully applied for deposition of Sb 2 Se 3 , which obtained a decent PCE. [98] CSS approach has yet rarely been applied for Sb 2 S 3 deposition.…”

An In-Depth Analysis of CdTe Thin-Film Deposition on Ultra-Thin Glass Substrates via Close-Spaced Sublimation (CSS)

“…The distance of source and substrate in the CSS method was fixed at 1 mm (Figure 1c) to reduce the loss possibility or undesired mass scattering during the sublimation process [16]. Other reports are available presenting the detailed strategies used in the CSS method [5]. The deposition rate R is an inverse function of source temperature T SO and Boltzmann constant k, as shown in Equation (1) [6].…”

“…However, there is an extremum, namely, the glass transformation temperature (Tg = 560 • C) to be considered during the thin-film deposition on the flexible glass substrate [4]. As a result, regulating the deposition pressure during the sublimation process is an effective way to further improve thin-film specifications [5]. Related earlier studies demonstrated the effect of sublimation pressure on the mechanism of the CSS deposition system on normal borosilicate (1.1 to 3 mm thick) glass.…”