A study of the self-healing phenomenon of Cu2ZnSn(S, Se)4 (CZTSSe) solar cells has shown more than 10% enhancement in cell performance after storage at room temperature for a week, with a significant improvement in the open-circuit photovoltage (Voc) and fill factor (FF). In addition, up to 10.45% power conversion efficiency (PCE) has been achieved. No obvious change in crystallinity, crystal phase, optical absorption or elemental distribution in the CZTSSe films was detected on examining the x-ray diffraction (XRD) pattern, Raman spectrum, ultraviolet-visible (UV-Vis), and TOF-SIMS. Further investigations on the charge carrier concentration, charge radiative recombination, and band structure suggest that the enhancement in PCE stems mainly from a reduction in deep defects of the CZTSSe semiconductor film.
Guoqiang Zhang,Xiaojun Zhang,Yangsen Xu,Peixin Zhang,Yongliang Li,Chuanxin He,Hongwei Mi
The role of defects in photocatalysis is rarely investigated more intuitively from the perspective of defect ionization energy (DIE), although it is the most important parameter for evaluating the depth of defect traps. Here, the crystalline poly(heptazine imide) (PHI) is adopted as an illustrative example to optimize the DIE and charge separation by regulating the carbon doping contents, ultimately activating the near-infrared photocatalytic activity . Shallow defect traps induced by doping (DIE < 25 meV) facilitate charge separation by releasing shallowly trapped carriers. In contrast, deep defect traps (DIE > 25 meV) act as non-radiative recombination centers , causing carrier quenching. More importantly, the non-radiative recombination rate in PHI is 1–2 orders of magnitude faster than the radiative recombination rate , so suppressing non-radiative recombination is more important for improving charge separation efficiency. Our work elucidates the role of defects in photocatalysis more intuitively from the perspective of DIE, and establishes a discernible relationship between DIE and photocatalytic activity .
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