Effects of Different Fluorine Dopants on the Properties of the Tin Oxide Window Layer and CdTe/CdS Solar Cell

Abstract

AbstractConductive tin-oxide (SnO2) film is doped by group V or VII elements. Of all possible dopants, fluorine provides n-type SnO2 with the best electronic and optical properties. However, the commonly used fluorine dopant, bromotrifluoromethane (CBrF3), is a greenhouse gas. Thus, an alternative fluorine source is needed. In this work, we compared CIF3 as a fluorine dopant to CBrF3. With CBrF3 dopant, optimized carrier concentration and electron mobility values can reach to mid 1020 cm-3 and over 40 cm2/V-s, respectively. After carrier concentration saturates, the electronic mobility continues to improve with an increase of CBrF3 dopant concentration. As a comparison, to achieve similar carrier concentration, far less CIF3 dopant is required. However, the electron mobility is lower (<30 cm2/V-s) and does not improve with an increase of dopant concentration. The low electron mobility increases the optical absorption, especially of long wavelengthes. Considering CdTe/CdS solar cell efficiency, the device with a CIF3-doped SnO2 window layer provides the lower photocurrent.