Organometal trihalide perovskites are emerging as very promising photovoltaic materials,
which is rivaling that of single crystal silicon solar cells despite their polycrystalline nature
with relatively high density of grain boundaries (GBs). There is a lack of understanding of the
effects of GBs on halide perovskites as their presence in silicon and other photovoltaic
materials is generally detrimental to their photovoltaic properties. Using first-principles
calculations, we systematically investigate the geometric structures of high-angle tilt GBs in …