An in-situ room temperature route to CuBiI4 based bulk-heterojunction perovskite-like solar cells

Both bismuth and copper are non-toxic and earth-abundant elements suitable for lead-free halide perovskite-like photovoltaic devices. Here, we report a highly facile route for in-situ producing copper-bismuth-iodide (CuBiI 4 ) thin films directly on ITO substrate at room temperature, by utilizing a Bi-Cu alloy layer as precursor. X-ray diffraction and transmission electron microscopy (TEM) results verified the formation of well crystallized CuBiI 4 thin films with [222] orientation. The transient photovoltage (TPV) analysis revealed that the CuBiI 4 is an n-type semiconductor with a suitable band gap of ~1.81 eV, preferable to photoelectric conversion compared with CH 3 NH 3 PbI 3 . It is very interesting that the subsequent spin-coating process of the classical Spiro-MeOTAD organic solution with TBP and acetonitrile resulted in a dense and smooth CuBiI 4 :Spiro-MeOTAD bulk-heterojunction film. The preliminarily fabricated simple sandwich structures of ITO/CuBiI 4 :Spiro-MeOTAD/Au hybrid solar cell devices displayed efficient photovoltaic performance with the PCE up to 1.119% of the best sample. The room temperature direct metal surface elemental reaction (DMSER) method may provide a new insight for all-inorganic lead free perovskite-like A a B b X x compounds and high performance photovoltaic devices.