Charge separation quantum yield regions

Transient states generated from PH Hj. Absorbance transients generated from the P%Hm state provide a calibration for the extent of the absorbance changes which can be expected for a charge separation with a quantum yield of 1. Fig. 1 shows transient spectra in the 760 to 900 nm region recorded with 1.5 ps time resolution from the PHlHj Q state at 90 K. The multichannel detection was not sensitive beyond 900 nm. 

A common feature of the hole drilling experiments described above is that they were performed without electrochemical control of the semiconductor surface. As a result, quantum yields were always much less than unity and thewidth of the space charge region was probably very low. The latter factor doubtlessly magnified differences between quantum yields observed for ultraviolet and visible light resulting from differences in the penetration depth and hence efficiency of electron-hole separation. T o date, no studies of the effects of electrode bias on the rates and profiles of laser drilled structures have been presented. 

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