Georgi Nadjakov or also spelled Georgi Nadzhakov, Георги Наджаков was born in Dupnitsa, Bulgaria on 26 December 1896 and died on 24 February 1981 (aged 84) Sofia. He was a Bulgarian physicist and became a member of the Bulgarian Academy of Sciences (1945), a corresponding member of the Göttingen Academy of Sciences (1940) in Germany, and a member of the Russian Academy of Sciences (1958).
He studied mathematics and physics during the First World War and graduated from the University of Sofia.
Experimentally investigated photoconducting properties of sulphur, Georgi Nadjakov prepared for the first time the permanent photoelectret state of matter and in 1937  and 1938 published his paper. He made an electret with light and electricity. The new electret was called photoelectret. The previous type of electret, obtained by heat and electricity, discovered by Mototaro Eguchi in 1919, was called by him thermoelectret. Georgi Nadjakov called the electret discovered by him in 1937, photoelectret.
This most notable achievement of Nadjakov, photoelectrets, led to the invention of the practical application of the photocopier by Chester Carlson some years later.
- Nadjakov Glacier on Graham Land in Antarctica is named after Georgi Nadjakov.
- Institute of Solid State Physics is since 1982 known as Georgi Nadjakov Institute of Solid State Physics. Its predecessor was founded by Georgi Nadjakov in 1946.
- “Georgi Nadjakov, SUR UNE NOUVELLE ESPECE DE POLARISATION PERMANENTE DES DIELECTRIQUES”. Comptes Rendus de l’Académie des Sciences de Paris. 204: 1865–1866. 1937.
- “G. Nadjakov, UBER EINE NEUE ART VON ELEKTRETEN: PHOTOELEKTRETEN”. Physikalische Zeitschrift. 39 (6): 226–227. 1938.
- “Photoelectret State of Matter”.
- Kao, Kwan-Chi (2004). “5: Electrets”. Dielectric Phenomena in Solids. Academic Press. p. 283. ISBN 978-0123965615. Retrieved 12 November 2013.
Photo credit: History of Physics Museum Wikimedia