Hybrid P3HT/CdSe photovoltaic cells: Effects of nanocrystal size and device aging

Hybrid solar cells based on conjugated polymers and colloidally synthesized inorganic nanoparticles have been recognized as an alternative to all-organic solar cells due to the intrinsically higher charge transport property in inorganic component. In this work, CdSe nanoparticles with different sizes, served as the electron acceptor, have been used together with poly (3-hexylthiophene) (P3HT) as the active layer for the hybrid solar cells. The power-conversion efficiency (η_P) of these devices strongly depends on the size of the CdSe nanoparticles, increasing from ηp ∼0.5% for 4.0 nm size nanoparticles to η_p ∼2.4% for 6.8 nm size nanoparticles under AM 1.5 G solar illumination. Furthermore, the devices also exhibit an unusual initial aging period when exposed to the air, which results in a significant enhancement in the short-circuit current, open-circuit voltage and power conversion efficiency.