Examination of the carrier lifetime and diffusion length in PbS quantum dot solar cells employing PbS-I,Cl photoactive layers

The differences in carrier lifetime and diffusion length in quantum dot bulk heterojunction solar cells incorporating iodide and chloride-capped lead sulfide are examined as a function of photoactive layer (PAL) construction via complementary instrumental techniques. Specifically, photoactive layers are created by spin or blade coating a PbS-I,Cl ink onto a zinc oxide electron transport layer. A hole transport layer consisting of lead sulfide quantum dots capped with 1,2-ethanedithiol formed through solid state ligand exchange is applied atop the PAL. Carrier lifetimes and diffusion lengths are measured via open circuit photovoltage decay and time dependent photocurrent decay, respectively. These results are compared with those obtained by intensity modulated photovoltage and photocurrent spectroscopies.