This book covers in a textbook-like fashion the basics or organic solar cells, addressing the limits of photovoltaic energy conversion and giving a well-illustrated introduction to molecular electronics with focus on the working principle and characterization of organic solar cells. Further chapters based on the author’s dissertation focus on the electrical processes in organic solar cells by presenting a detailed drift-diffusion approach to describe exciton separation and charge-carrier transport and extraction. The results, although elaborated on small-molecule solar cells and with focus on the zinc phthalocyanine: C60 material system, are of general nature. They propose and demonstrate experimental approaches for getting a deeper understanding of the dominating processes in amorphous thin-film based solar cells in general.
The main focus is on the interpretation of the current-voltage characteristics (J-V curve). This very standard measurement technique for a solar cell reflects the electrical processes in the device. Comparing experimental to simulation data, the author discusses the reasons for S-Shaped J-V curves, the role of charge carrier mobilities and energy barriers at interfaces, the dominating recombination mechanisms, the charge carrier generation profile, and other efficiency-limiting processes in organic solar cells. The book concludes with an illustrative guideline on how to identify reasons for changes in the J-V curve.
This book is a suitable introduction for students in engineering, physics, material science, and chemistry starting in the field of organic or hybrid thin-film photovoltaics. It is just as valuable for professionals and experimentalists who analyze solar cell devices.
Table of ContentsIntroduction.- Photovoltaic Energy Conversion.- Organic Solar Cells.- Modeling.- Simulation Study on Single-Layer Bulk-Heterojunction Solar Cells.- Influence of Injection and Extraction Barriers on Open-Circuit Voltage and J-V Curve Shape studied at a Variation of Hole Transport Layer and Donor Materials.- Imbalanced Mobilities causing S-shaped J-V Curves in Planar Heterojunction Solar Cells.- Open-Circuit Voltage and J-V Curve Shape of ZnPc:C60 Solar Cells with Effect of Concentration Gradients in ZnPc:C60 Bulk Heterojunction Solar Cells.- Role of the Generation Profile and Recombination in ZnPc:C60 Solar Cells.- Linear Saturation Behavior.- Main Results.- Further Analyses and Possible Extensions of the Simulation.