First-principles study of SrSnO3 as transparent conductive oxide br

As a wide band gap semiconductor with perovskite structure, SnSnO3 is regarded as a promising candidateof transparent conductive oxides due to its superior properties like high transparency, non-toxicity and lowprice. In this work, the electronic structure of SrSnO3 is obtained through first-principles calculations based onHSE06 hybrid functional. Especially, we investigate the defect formation energy and transition levels of theintrinsic and external defects in SrSnO3. The intrinsic defects including the anti-site defects (SrSn and SnSr), thevacancy defects (VSr, VSn, and VO), and the interstitial defects (Sri, Sni and Oi) are considered while theexternal doping defects are taken into account, including the substitution of Li, Na, K, Al, Ga, In for Sr site, Al,Ga, In, P, As, Sb for Sn site, and N, P at O site. Subsequently, the suitable doping elements and thecorresponding experimental preparation environments are pointed out. Furthermore, we discuss the mechanismof its conductance according to the energy positions of the band edges. Our calculation results demonstrate thatSrSnO3 is an indirect-type semiconductor with a fundamental band gap of 3.55 eV and an optical band gap of4.10 eV and then has a good visible light transmittance. Its valence band maximum (VBM) comes from O-2pstate while its conduction band minimum (CBM) mainly originates from Sn-5s state. In consistent with thedelocalized Sn-5s state at CBM, the electron effective mass is light and isotropic, which is beneficial to n-typeconductance. The n-type intrinsic defects SnSr and Vo have lower defect formation energy than the p-typeintrinsic defects under O-poor condition while the n-type and p-type defects with low defect formation energyare almost equal under O-rich condition. Moreover, the transition levels of SnSr and VO are both deep.Therefore, SrSnO3 cannot have a good conductance without external doping. Our calculations also demonstratethat it is hard to produce an efficient p-type external doping due to the compensation effect by VO. On theother hand, substitution of As or Sb for Sn site can result in an effective n-type external doping due to their lowdefect formation energy and shallow transition levels. According to the low energy positions of VBM (-7.5 eV)and CBM (-4.0 eV) of SrSnO3, we explain the reason why it is easy to realize an n-type conductance but hardto produce a high-performance p-type conductance, which follows the doping rules for wide band gapsemiconductors. Finally, Sb-doped SrSnO3 is proposed as a promising candidate for n-type transparent conductive materials