QUANTUM-DOT DETECTORS: Colloidal quantum-dot phototransistor could become solar-cell junction

摘要

A submonolayer of lead sulfide quantum dots on aluminum-doped zinc oxide forms a photo field-effect transistor; its bandgap is tunable to wavelengths suitable for use in photovoltaics. The concept of using a phototransistor to capture light instead of a photodiode or a photoconductor is an attractive one. A phototransistor--for example, a photo field-effect transistor (photoFET)--can potentially provide the gain of a photoconductive detector but with a lower dark current. To create a practical photoFET, four things must happen. First, photoelectrons must be transferred from the sensitizing material to the electron-accepting channel (EAC). Second, recirculation of secondary injected photocarriers flowing along the EAC should cause a photocurrent. Third, a sensitizing layer thick enough to absorb all the light should efficiently inject all carriers into the EAC. And finally, the EAC must be made thin enough to produce a low dark current.