  Lead halide perovskite solar cells have recently emerged as a very promising
photovoltaic technology due to their excellent power conversion efficiencies;
however, the toxicity of lead and the poor stability of perovskite materials
remain two main challenges that need to be addressed. Here, for the first time,
we report a lead-free, highly stable C6H4NH2CuBr2I compound. The C6H4NH2CuBr2I
films exhibit extraordinary hydrophobic behavior with a contact angle of
approximately 90 degree, and their X-ray diffraction patterns remain unchanged
even after four hours of water immersion. UV-Vis absorption spectrum shows that
C6H4NH2CuBr2I compound has an excellent optical absorption over the entire
visible spectrum. We applied this copper-based light absorber in printable
mesoscopic solar cell for the initial trial and achieved a power conversion
efficiency of 0.5%. Our study represents an alternative pathway to develop
low-toxic and highly stable organic-inorganic hybrid materials for photovoltaic
application.
