The past 2 years have seen the uniquely rapid emergence of a new class of solar cell based on mixed organic-inorganic halide perovskite. Grain boundaries are present in polycrystalline thin film solar cell, and they play an important role that could be benign or detrimental to solar-cell performance. Here we present efficient charge separation and collection at the grain boundaries measured by KPFM and c-AFM in CH3NH3PbI3 film in a CH3NH3PbI3/TiO2/FTO/glass heterojunction structure. We observe the presence of a potential barrier along the grain boundaries under dark conditions and higher photovoltage along the grain boundaries compare to grain interior under the illumination. Also, c-AFM measurement presents higher short-circuit current collection near grain boundaries, confirming the beneficial roles grain boundaries play in collecting carriers efficiently.

Thin silicon dioxide films were obtained by low-temperature plasma oxidation. Plasma oxidation was performed using a specially-designed new plasma source, called dual rotated spiral antenna (DuRoSA) system. This new plasma source produced high density plasmas (~ 1012 cm-3) having relatively low electron temperatures (2.5 ~ 4 eV). The temperature dependence of the plasma oxidation was found to be less sensitive than that of the high temperature thermal oxidation. The decrease in both oxidation rate and electron density with increasing oxygen fraction suggested that the negative oxygen ions may play the key role in plasma oxidation.

Deposition of N-doped poly-Si films from SiH 4 and NH 3 using a single wafer type low pressure chemical vapor deposition (LPCVD) system was investigated to improve the grain size reduction and the grain size distribution. The deposition rate and surface roughness of N-doped Si were greatly affected by the NH 3 /SiH 4 ratio such that they decreased with increasing NH 3 /SiH 4 ratio. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements revealed that with increasing NH 3 /SiH 4 ratio, the size of the grains was decreased and the grains size distribution became uniform. Finally, we successfully obtained N-doped poly-Si films having uniform grain size of approximately 6 nm.

Deposition of N-doped poly-Si films from SiH 4 and NH 3 using a single wafer type LPCVD system was investigated to improve the grain size reduction and the grain size distribution. The deposition rate and surface roughness of N-doped Si were greatly affected by the NH 3 /SiH 4 ratio such that they decreased with increasing NH 3 /SiH 4 ratio. XRD and TEM measurements revealed that with increasing NH 3 /SiH 4 ratio, the size of the grains was decreased and the grains size distribution got uniform. Finally, we successfully obtained N-doped poly-Si films having uniform grain size below 40 Å.