Properties and mechanism of solar absorber CdTe thin film synthesis by unipolar galvanic pulsed electrodeposition

摘要

Electrochemical deposition of CdTe semicon_ductor thin films over transparent conducting glass substrates by sequential unipolar current pulses is described. The magnitude of pulsed current and pulse periodicity affects the crystalline structure, morphology, optical absorbance and composition of CdTe films. CdTe films formed under high magnitude pulsed current density 5-15 mA cm~(-2) are crystalline with dominant cubic structure having (111) plane oriented parallel to the sub_strate. Stoichiometric CdTe film growth occurs with current pulses of short 25-300 ms periodicity and 3-50 ms duration. A mechanism of the CdTe growth involving in situ cathodic tellurization process step involving H_2Te formation and reaction with electrochemically deposited Cd monolayer is described. CdTe film growth in the pulsed electrodeposition occurs under mass transport conditions under strong influence of high magnitude pulsed current. This results in much higher growth rates__ 5-8 _m h~(-1) for CdTe films which is attractive for CdTe solar cells in a production environment.