CdSe Quantum-Dot-Sensitized Solar Cell with ∼100% Internal Quantum Efficiency

We have constructed and studied photoelectrochemical solar cells (PECs) consisting of a photoanode prepared by direct deposition of independently synthesized CdSe nanocrystal quantum dots (NQDs) onto a nanocrystalline TiO2 film (NQD/TiO2), aqueous Na2S or Li2S electrolyte, and a Pt counter electrode We show that light harvesting efficiency (LHE) of the NQD/TiO2 photoanode is significantly enhanced when the surface passivation is changed from tri n octylphosphine oxide(TOPO) to 4-butylamine (BA) In the PEC the use of NQDs with a shorter passivating ligand, BA, leads to a significant enhancement in both the electron injection efficiency it the NQD/TiO2 interface and charge collection efficiency at the NQD/electrolyte interface, with the latter attributed mostly to a more efficient diffusion of the electrolyte through the pores of the photoanode We show that by utilizing BA-capped NQDs and aqueous Li2S as an electrolyte, It is possible to achieve similar to 100% internal, quantum efficiency of photon to-electron conversion, matching the performance of dye sensitized solar cells