Nanostructured p-type cobalt layered double hydroxide/n-type polymer bulk heterojunction yields an inexpensive photovoltaic cell

A low-cost, environmentally benign method was used to prepare nanostructured thin films of Co5(OH)8(NO3)2·2H2O, a layered double hydroxide p-type semiconductor. When infilled with poly(3-butylthiophene) (P3BT), an n-type semiconducting polymer, the resulting hybrid bulk heterojunction yields a photovoltaic device. The indium-doped tin oxide/Co5(OH)8(NO3)2·2H2O/P3BT/Al cell described here is an unprecedented example of an optoelectronic device fabricated by a low-cost biologically inspired pathway independent of organic structure-directing agents. Under illumination, this proof-of-principle device yields an open circuit voltage of 1.38 V, a short circuit current of 9 μA/cm2, a fill factor of 26% and a power efficiency of 3.2·10− 3%. While the open circuit voltage of this prototype cell is close to its theoretical maximum, potential sources of the observed low efficiency are identified, and a suggested path for improvement is discussed.