Ballabio Marco, Fuertes Marrón David, Barreau Nicolas, Bonn Mischa, Cánovas Enrique
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
Instituto de Energía Solar, Universidad Politécnica de Madrid, ETSI Telecomunicación, Avda. Complutense 30, 28040, Madrid, Spain.
Adv Mater. 2020 Mar;32(9):e1907763. doi: 10.1002/adma.201907763. Epub 2020 Jan 27.
The bandgap of CuIn Ga Se (CIGS) chalcopyrite semiconductors can be tuned between ≈1.0 and ≈1.7 eV for Ga contents ranging between x = 0 and x = 1. While an optimum bandgap of 1.34 eV is desirable for achieving maximum solar energy conversion in solar cells, state-of-the-art CIGS-based devices experience a drop in efficiency for Ga contents x > 0.3 (i.e., for bandgaps >1.2 eV), an aspect that is limiting the full potential of these devices. The mechanism underlying the limited performance as a function of CIGS composition has remained elusive: both surface and bulk recombination effects are proposed. Here, the disentanglement between surface and bulk effects in CIGS absorbers as a function of Ga content is achieved by comparing photogenerated charge carrier dynamics in air/CIGS and surface-passivated ZnO/CdS/CIGS samples. While surface passivation prevents surface recombination of charge carriers for low Ga content (x < 0.3; up to 1.2 eV bandgap), surface recombination dominates for higher-bandgap materials. The results thus demonstrate that surface, rather than bulk effects, is responsible for the drop in efficiency for Ga contents larger than x ≈ 0.3.
对于Ga含量在x = 0至x = 1之间的情况，铜铟镓硒（CIGS）黄铜矿半导体的带隙可在≈1.0至≈1.7 eV之间调节。虽然太阳能电池实现最大太阳能转换所需的最佳带隙为1.34 eV，但对于Ga含量x > 0.3（即带隙>1.2 eV）的情况，基于CIGS的先进器件的效率会下降，这一因素限制了这些器件的全部潜力。作为CIGS成分函数的有限性能背后的机制仍然难以捉摸：有人提出了表面和体相复合效应。在这里，通过比较空气/CIGS和表面钝化的ZnO/CdS/CIGS样品中的光生电荷载流子动力学，实现了CIGS吸收体中表面和体相效应随Ga含量的解缠。虽然表面钝化可防止低Ga含量（x < 0.3；带隙高达1.2 eV）时电荷载流子的表面复合，但对于高带隙材料，表面复合占主导。因此，结果表明，对于Ga含量大于x≈0.3的情况，效率下降是由表面而非体相效应导致的。
