Investigation of conductivity of adhesive layer including indium tin oxide particles for multi-junction solar cells

We report connection conductivity ( (C_{rm c}) ) of adhesive which including (hbox {In}_2hbox {O}_3) – (hbox {SnO}_2) (ITO) particles developed for fabrication of stacked-type-multi-junction solar cells. The commercial 20- (upmu ) m sized ITO particles were heated in vacuum at temperature ranging from 800 to 1,300  (^{circ }{rm C}) for 10 min to increase (C_{rm c}) . 6.2 wt% ITO particles were dispersed in commercial Cemedine adhesive gel to form 100 samples structured with n-type Si/adhesive/n-type Si (n-Si sample) and p-type Si/adhesive/p-type Si (p-Si sample). Current density as a function of voltage (J–V) characteristics gave (C_{rm c}) . It ranged from 4.3 to 1.0 S/cm (^2) for the n-Si sample with 800 (^{circ }{rm C}) heat-treated ITO particles. Its standard deviation was 0.59 S/cm (^2) . On the other hand, it ranged from 2.0 to 0.6 S/cm (^2) for the p-Si sample with 800  (^{circ }{rm C}) heat-treated ITO particles. Its standard deviation was 0.22 S/cm (^2) . The distribution of (C_{rm c}) mainly resulted from contact efficiency of ITO particles to substrate. We theoretically estimated that present (C_{rm c}) achieved a low loss of the power conversion efficiency ( (E_{rm ff}) ) lower than 0.3 % in the application of fabrication of multi-junction solar cell with an intrinsic (E_{rm ff}) of 30 % and an open circuit voltage above 1.9 V.