PD Dr. Thomas Dittrich
Helmholtz Center Berlin for Materials and Energy
Abstract
Surface
photovoltage (SPV) techniques are very sensitive to spatial
regions where separation of photo-generated charge carriers
takes place. SPV can provide information about electronic states
and carrier dynamics being useful for a better understanding and
development of solar cell materials. Experimental conditions
over broad scales of time, photon energy, temperature and
ambience can be realized with SPV measurements in the
Kelvin-probe and fixed capacitor arrangements. Possibilities of
SPV will be demonstrated on three selected topics about (i)
differences in charge separation at Cu(In,Ga)Se2 /
CdS and Cu(In,Ga)Ses / In2S3
hetero-junctions, (ii) charge separation in systems with
molecular donor-acceptor spiro-compounds and (iii) the role of
surface treatments for charge separation in colloidal quantum
dot layers. It has been shown, for example, that surface states
at CdSe quantum dots strongly depend on surfactant exchange and
that the density and distribution of related surface states can
be deduced from transient SPV measurements within a single
quantum dot approximation model.
