Technological Background and Properties of Thin Film Semiconductors

Especially with the development of nanotechnology and polymer science, interest in research and production of both efficient and lower-cost semiconductor thin film materials is increasing day by day. The use of nano-structured thin films for efficient use of solar cells in production of n-type semiconductor materials is one of the most important sources of energy and new-generation energy. Considering the indicated trends and energy requirements, it has been important to transfer this technology in detail regarding the surface technologies related to the semiconductor materials produced with thin film technologies instead of bulk materials. With this aim, this book chapter “Technological Background and Properties of Thin Film Semiconductors” includes a brief story about semiconductors, band gap theory, thin film applications, and besides traditional thin film processing methods finally a new technology called aerosol deposition technique which allows room temperature processing of several materials for semiconductor applications, respectively. It is thought that it will make important contributions to the relevant field and bring a new perspective and direct scientific research in “process-structure–property-performance” relation.

Study of transport parameters and defect states in thin film perovskites under different environments − air or vacuum − and after light-soaking

We present some advanced characterization techniques developed to investigate on the opto-electronic properties of thin film semiconductors and apply them to perovskite layers. These techniques are the steady state photocarrier grating (SSPG) and the Fourier transform photocurrent spectroscopy (FTPS). The SSPG was developed to study the ambipolar diffusion length of carriers and the FTPS was imagined to measure the variations of the below gap absorption coefficient with the light energy, giving information on the defect densities of the gap responsible for this absorption. The potentialities of these techniques are first detailed and then exemplified by their application to thin film perovskites. To study their stability, these films were exposed to different environments, air or vacuum, and in their as-deposited state or after light-soaking with heavy light. We find that the diffusion length and density of states are quite stable, even after light-soaking, and suggest that the degradation of devices exposed to 1 sun mainly comes from the evolution of the contacts instead of the perovkite itself.