Research on high-efficiency, single-junction, monolithic, thin-film amorphous silicon solar cells

This report present results of the third phase of research in high-efficiency, single-junction, monolithic, thin-film, a-Si solar cells. Six glow-discharge deposition systems, including an in-line multichamber system, were used to grow both doped and undoped a-Si films. In single load-lock system, a-Si was deposited over 1000- cm{sup 2} substrates with less then a 1% variation in thickness and low oxygen impurity levels. The system produced 1000-cm{sup 2} submodules with active-area efficiencies of 8.7%. A model was developed for light scattering in textured tin oxide that predicts scattered transmission through the air/glass/tin oxide/air configuration to within a few percent. Textured tin oxide films were grown by chemical vapor deposition using tin tetrachloride. Solar-cell efficiencies of about 11% were obtained in small-area p-i-n cells with reflective back contacts of Ti/Ag that exhibit external quantum efficiencies as high as 58.7% at 700 nm; other cells with ITO/Ag back contacts have had quantum efficiencies as high as 64% at 700 nm. High-performance cells were fabricated by employing dopant and carbon concentration gradients near the p/i interface. Total-area efficiencies around 8% were obtained for submodules in which the patterning was done by laser scribing. 11 refs., 35 figs., 18 tabs.