Enhancing the Performance of Aqueous Solution-Processed Cu(2)ZnSn(S,Se)(4) Photovoltaic Materials by Mn(2+) Substitution

In this work, the Cu(2)Mn(x)Zn(1−x)Sn(S,Se)(4) (0 ≤ x ≤ 1) (CMZTSSe) alloy films were fabricated by a sol-gel method. Meanwhile, the effects of Mn substitution on the structural, morphological, electrical, optical, and device performance were studied systematically. The clear phase transformation from Cu(2)ZnSn(S,Se)(4) (CZTSSe) with kesterite structure to Cu(2)MnSn(S,Se)(4) (CMTSSe) with stannite structure was observed as x = 0.4. The scanning electron microscope (SEM) results show that the Mn can facilitate the grain growth of CMZTSSe alloy films. Since the x was 0.1, the uniform, compact, and smooth film was obtained. The results show that the band gap of the CMZTSSe film with a kesterite structure was incessantly increased in a scope of 1.024–1.054 eV with the increase of x from 0 to 0.3, and the band gap of the CMZTSSe film with stannite structure was incessantly decreased in a scope of 1.047–1.013 eV with the increase of x from 0.4 to 1. Meanwhile, compared to the power conversion efficiency (PCE) of pure CZTSSe device, the PCE of CMZTSSe (x = 0.1) device is improved from 3.61% to 4.90%, and about a maximum enhanced the open-circuit voltage (V(OC)) of 30 mV is achieved. The improvement is concerned with the enhancement of the grain size and decrease of the Cu instead of Zn (Cu(Zn)) anti-site defects. Therefore, it is believed that the adjunction of a small amount of Mn may be an appropriate approach to improve the PCE of CZTSSe solar cells.