Light management of a-SiOx:H thin film solar cells with hydrogen-reduced p+ buffer at TiO2/p-layer interface

In this study, light-management approaches for amorphous silicon oxide (a-SiOx:H) thin film solar cells were developed. First, to enhance back reflection in the device, an Al-doped ZnO (AZO) film was introduced at the back interface between n-type nanocrystalline silicon oxide (n-nc-SiOx:H) and Ag. In addition, we successfully suppressed optical losses at front interfaces by employing anti-reflection layers of MgF2 at air/Asahi-VU and TiO2 at Asahi-VU/p-layer interfaces. These light-managing techniques contributed to the enhancing of the short circuit current density (Jsc) from 9.88 to 11.42 mA/cm2, resulting in an increase in efficiency from 7.35% to 8.15%. We next replaced AZO/p-nc-SiOx:H conventional buffer layers inserted at the TiO2/p-layer interface by developing a hydrogen-reduced p+ buffer layer to remove the AZO protection layer. The new TiO2/buffer structure was found to be beneficial for attaining a good fill factor (0.738) and open circuit voltage (1.013 V) by avoiding hydrogen plasma damages; this, improved the efficiency of the a-SiOx:H solar cell up to 8.40% when using a very thin absorber of only 100 nm.