Remarkable enhancement of stability in high-efficiency Si-quantum-dot heterojunction solar cells by employing bis(trifluoromethanesulfonyl)-amide as a dopant for graphene transparent conductive electrodes

Abstract

The efficiency and long-term stability of graphene (GR)/Si quantum dots-embedded SiO2 heterojunction solar cells are remarkably enhanced by employing bis(trifluoromethane sulfonyl)–amide (TFSA) as a dopant for GR. With increasing the doping concentration (nD) to 30 mM, the sheet resistance of the TFSA-doped GR transparent conductive electrode sharply decreases to ∼191 Ω/sq with only 1% reduction in its transmittance at 550 nm. The DC conductivity/optical conductivity ratio saturates to ∼62.5 at nD = 20 mM, resulting in maximum power conversion efficiency (PCE) of 16.61% and almost no loss of the PCE under 25 °C and 40% humidity atmosphere for 700 h. The solar cell also maintains ∼94% (absolutely from 16.61 to 15.57%) of its initial PCE even under continuous light soaking of 1 Sun at 60 °C and 30% humidity for 1000 h.