An efficiency of 12.4% has been reached with

flexible cadmium telluride (CdTe) thin-film solar cells by EMPA, the

Swiss Federal Laboratories for Materials Testing and Research in


Dubendorf, Switzerland.

The laboratory for thin Films and Photovoltaics

attached flexible CdTe thin-film solar cells on a lightweight polyimide

film by sing low temperatures (<450°C) vacuum evaporation process to

grow cadmium sulphide/cadmium telluride (CdS/CdTe) layers and a

subsequent annealing step in air where the materials are heated up and

cooled down to harden them.

The researchers used zinc oxide doped

on aluminium (ZnO:Al) as a transparent electric contact instead of the

expensive indium tin oxide (ITO) layer used in earlier 11.4% solar


In addition to being cheaper, the ZnO/ZnO:Al bi-layer

improved process yield and reproducibility of high efficiency solar

cells, EMPA says.


12.4% efficiency of the flexible thin-film solar cells was measured

under standard AMI.5 illumination condition. The parameters were Voc =

823 mV, Jsc = 19.6, FF = 76.5%.

EMPA says all the process

steps of the flexible thin-film solar cells are compatible with

continuous in-line processing and can be transferred to roll-to-roll

manufacturing of large area solar modules with high deposition speed.


high efficiency flexible CdTe solar cells can become a low cost option

for cost-effective solar electricity generation in near future,” EMPA


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