Using thin AZO layers coupled with SiNx:H as a way to decrease Indium consumption in SHJ cells and modules

Abstract

In this work, we investigate the possibility of replacing Indium-rich transparent conductive oxides (TCO) with previously untested thin aluminum-doped zinc oxide (AZO) layers (50–30 nm) as a way to remove Indium in SHJ solar cells and modules. In order to maintain optical properties and possibly to increase the damp heat reliability of the modules using those thin AZO layers, optically optimized SiN_x:H capping layers were used. The AZO deposition conditions were fine-tuned (varying the gas flows), and the best AZO/SiN_x:H combinations were then selected based on the output of optical simulations, fed with characterization results. On the front side, when deposited on the classical (n) a-Si:H selective layers, the thinner AZO layers yielded lower FF due to higher contact resistivity as well as higher R_sheet. However, when deposited on (n) nc-Si:H, the contact resistivity was drastically lowered, allowing cells with 30 nm AZO layers to achieve comparable efficiencies as the cells incorporating ITO layers both at cell (22.88 %) and module (21.67 %) scale. On the rear side, the AZO layers yielded −0.5 %_abs efficiency losses compared to the reference cells, due to both FF and J_sc losses. Reliability tests in damp heat environment (up to 1000 h) were conducted and showed that on the front side, thinner AZO layers show increased sensibility to humidity, and that SiN_x:H layers increase the degradation. On the rear side, AZO layers suffer less from humidity degradation, and the resistance is enhanced with a 10 nm ITO capping layer.