Photodetectors based on treated CdSe quantum-dot films

We demonstrate photodetectors of sandwich geometry active in the visible spectrum in which the active layer is a 200 nm thick film of CdSe quantum dots (QDs). The solution-phase treatment of the QD film with n-butylamine after casting greatly increases the exciton dissociation efficiency and charge-transport properties of the film. Under 110 mW/cm(2) illumination with light at lambda=514 nm, the photocurrent to dark current ratio, I-photo/I-dark, is 10(3) at V=0 V, and the 3 dB frequency is similar to 50 kHz. At room temperature, we observe zero-bias external quantum efficiencies (EQE) from 0.08% to 0.23% in the wavelength range lambda=350 nm to lambda=575 nm, corresponding to an internal quantum efficiency (IQE) of 0.6 +/- 0.1% across the tested spectrum. At V=-6 V, EQE ranges from 15% to 24%, corresponding to an IQE of 70 +/- 10%. (c) 2005 American Institute of Physics.