Resonant energy transfer in light harvesting and light emitting applications

The performance of light emitting and light harvesting devices is improved by utilising resonant energy transfer. In lighting applications, the emission energy of a semiconductor heterostructure and the absorption of organic dyes or colloidal quantum dots (QDs) are engineered so that the excitations in the semiconductor heterostructure can be transferred to the light emitters by means of resonant energy transfer. The emitters subsequently emit colour-tunable light ranging from the visible to the near-infrared. As a result, a twofold enhancement of QD emission is demonstrated in a hybrid QD/semiconductor heterostructure. In light harvesting applications, a hybrid structure of colloidal QDs and a quantum well (QW) p-i-n heterostructure is investigated. After highly absorbing QDs absorb photons, the excitations are efficiently transferred to a QW p-i-n heterostructure via resonant energy transfer. The generated electron-hole pairs in the heterostructure are subsequently separated by the built-in electric held and collected by the corresponding electrodes. In order to increase the energy transfer rate, the donor-acceptor separation distance is minimised by fabricating channel structures on the heterostructure surface penetrating its active layers. Consequently, a sixfold enhancement of photocurrent conversion efficiency is demonstrated. Photocurrent of the hybrid structure is further improved by replacing the QW heterostructure with a bulk p-i-n heterostructure which has higher carrier transport efficiency. Hence, the photocurrent of the hybrid bulk heterostructure is about two orders of magnitude higher than that of the hybrid QW heterostructure. The proposed hybrid structures offer efficient light harvesting devices where high absorption of the colloidal QDs is utilised and their low charge-transfer is overcome.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2009

Author dc:creator

• Chanyawadee, Soontorn

Advisor dc:contributor.advisor

• Lagoudakis, P.