Investigation of materials for solar energy conversion by surface photovoltage techniques
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.