CdSe nanoplatelets have large extinction coefficients and, at low temperatures, very fast photoluminescence lifetimes. To explain these observations, the giant oscillator strength (GOST) effect has been hypothesized to exist in semiconductor nanoplatelets. In principle, GOST suggests that the coherence area of excitons can reach the full size of the nanoplatelet, increasing oscillator strength proportional to the physical size of the nanoplatelet. However, at high temperatures, there is a substantial discrepancy between the large extinction coefficient of nanoplatelets measured in absorption measurements with the oscillator strength estimated from the optical stark effect and the measured exciton coherence area. Using temperature-dependent measurements of CdSe nanoplatelets, both optical stark effects and measurements of bleaching intensity show that this discrepancy with GOST persists to as low as 2.5 K.

Using real and virtual excitons to examine the giant oscillator strength effect in nanoplatelets

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