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Room-temperature sputtered tungsten-doped indium oxide for improved current in silicon heterojunction solar cells

Abstract:

The window layers limit the performance of silicon heterojunction (SHJ) solar cells with front and back contacts. Here, we optimized tungsten-doped indium oxide (IWO) film deposited by radio frequency magnetron sputtering at room temperature. The opto-electrical properties of the IWO were manipulated when deposited on top of thin-film silicon layers. The optimal IWO on glass shows carrier density and mobility of 2.1 × 1020 cm−3 and 34 cm2 V−1s−1, respectively, which were tuned to 2.0 × 1020 cm−3 and 47 cm2 V−1s−1, as well as 1.9 × 1020 cm−3 and 42 cm2 V−1s−1, after treated on i/n/glass and i/p/glass substrates, respectively. Using the more realistic TCO data that were obtained on thin-film silicon stacks, optical simulation indicates a promising visible-to-near-infrared optical response in IWO-based SHJ device structure, which was demonstrated in fabricated devices. Additionally, by adding an additional magnesium fluoride layer on device, the champion IWO-based SHJ device showed an active area cell efficiency of 22.92%, which is an absolute 0.98% efficiency gain compared to the ITO counterpart, mainly due to its current gain of 1.48 mA/cm2.