The bifunctional tin-doped indium oxide as hole-selective contact and collector in silicon heterojunction solar cell with a stable intermediate oxide layer

The tin-doped indium oxide (ITO) and the intermediate nanometer-scale SiOx layers were synthesized directly on n-type crystalline silicon (n-Si) substrate by radio-frequency magnetron sputtering deposition. During the ITO-sputtering deposition, the effect of shallow implantation intermixing led to forming an ultra-thin SiOx layer, which could successfully lessen the interface states and promote the transportation of carriers. The photovoltaic properties of devices showed the open-circuit voltage (V-ac) strongly correlated to the carrier concentration of ITO (n(ITO)), indicating a hole-selective contact of ITO. An equivalent "p-type Fermi level" (hole as majority carriers) was reasonably employed to interpret the decrease of V-oc with the increase of n(ITO). The impact of the work function difference between ITO and n-Si on V-oc of ITO/SiOx/n-Si heterojunction cells was tentatively equivalent to the difference of the defined quasi-Fermi levels. Through the modification of surface-reflectance and rear contact, the heterojunction structure solar cells achieved efficiency of 11.50 +/- 0.17%. Furthermore, the stability of the devices in conversion efficiency was excellent over a whole year. The temperature coefficient of -0.34%/degrees C was obtained, which was better than -0.45%/degrees C of a typical diffused junction silicon solar cell. (C) 2017 Elsevier Ltd. All rights reserved.