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

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 x 10(20) cm(-3) and 34 cm(2) V(-1)s(-1), respectively, which were tuned to 2.0 x 10(20) cm(-3) and 47 cm(2) V(-1)s(-1), as well as 1.9 x 10(20) cm(-3) and 42 cm(2) V(-1)s(-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/cm(2).

Automated summary

This study optimized the tungsten-doped indium oxide film deposited by radio frequency magnetron sputtering at room temperature to improve the performance of silicon heterojunction solar cells. Optical simulation indicated a promising optical response in IWO, which was confirmed in fabricated devices. By adding an additional magnesium fluoride layer on the device, the IWO-based SHJ device achieved a higher efficiency compared to the ITO counterpart, mainly due to its current gain.