Li H, Liu X X, Lin Y S, Yang B, Du Z M
The Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China.
Phys Chem Chem Phys. 2015 May 7;17(17):11150-5. doi: 10.1039/c5cp00564g.
The effect of grain boundaries (GBs), in particular twin boundaries (TBs), on CdTe polycrystalline thin films is studied by conductive atomic force microscopy (C-AFM), electron-beam-induced current (EBIC), scanning Kelvin probe microscopy (SKPM), electron backscatter diffraction (EBSD), and scanning transmission electron microscopy (STEM). Four types of CdTe grains with various densities of {111} Σ3 twin boundaries (TBs) are found in Cl-treated CdTe polycrystalline thin films: (1) grains having multiple {111} Σ3 TBs with a low angle to the film surface; (2) grains having multiple {111} Σ3 TBs parallel to the film surfaces; (3) small grains on a scale of not more than 500 nm, composed of Cd, Cl, Te, and O; and (4) CdTe grains with not more than two {111} Σ3 TBs. Grain boundaries (including TBs) exhibit enhanced current transport phenomena. However, the {111} Σ3 TB is much more beneficial to micro-current transport. The enhanced current transport can be explained by the lower electron potential at GBs (including TBs) than the grain interiors (GIs). Our results open new opportunities for enhancing solar cell performances by controlling the grain boundaries, and in particular TBs.
通过导电原子力显微镜（C-AFM）、电子束诱导电流（EBIC）、扫描开尔文探针显微镜（SKPM）、电子背散射衍射（EBSD）和扫描透射电子显微镜（STEM）研究了晶界（GBs），特别是孪晶界（TBs）对碲化镉多晶薄膜的影响。在经氯处理的碲化镉多晶薄膜中发现了四种具有不同密度{111}Σ3孪晶界（TBs）的碲化镉晶粒：（1）具有多个与薄膜表面低角度的{111}Σ3 TBs的晶粒；（2）具有多个平行于薄膜表面的{111}Σ3 TBs的晶粒；（3）尺寸不超过500nm的小晶粒，由镉、氯、碲和氧组成；（4）具有不超过两个{111}Σ3 TBs的碲化镉晶粒。晶界（包括TBs）表现出增强的电流传输现象。然而，{111}Σ3 TB对微电流传输更有益。电流传输增强可以用晶界（包括TBs）处的电子势低于晶粒内部（GIs）来解释。我们的结果为通过控制晶界，特别是TBs来提高太阳能电池性能开辟了新的机会。
