Monolithically integrated flexible Cu(In,Ga)Se 2 solar cell submodules

Abstract

Monolithically integrated Cu(In,Ga)Se 2 (CIGS) solar cell submodules with 15% efficiencies have been demonstrated on flexible ceramic and thin soda-lime glass (SLG) substrates. For ceramic substrates, alkali-doping control was performed using alkali–silicate glass thin layers deposited prior to the sputtering of the Mo back contact layer. An independently certified 15.9% submodule efficiency (17 cells, aperture area 75.7 cm 2) was demonstrated for a ceramic substrate. Thin SLG substrates are often distorted due to the high temperatures required for CIGS growth, which leads to thermal expansion induced stress from the Mo back contact layer. To avoid this problem, which can lead to difficulties in the subsequent mechanical scribing process, lower CIGS growth temperatures or thinner Mo back contact layers are necessary. In the present work, a radio frequency (rf)-plasma cracked Se radical beam source (R-Se), which can enhance the efficiency of low temperature grown CIGS solar cells, was used as a Se source and CIGS layers were grown at relatively low temperature. Submodule efficiencies of 15.0% (17 cells, aperture area 76.5 cm 2) and 14.5% (17 cells, aperture area 51.0 cm 2) were demonstrated on 400 and 200 nm thick Mo layer coated 250 μm thick SLG substrates, respectively.