Photocharging of MaterialsOleksandr Savateev*Am Mühlenberg 1, Potsdam, 14476, Germany E-mail: email@example.comKeywords: photodoping, photocharging, semiconductor, photocatalysis, organic synthesis, hydrogen storage, solar batteryPhotocharging or photodoping is a process in which electrons are accumulated in a semiconductor upon band gap excitation followed by quenching of the photogenerated holes by reductants. In semiconductors with excess of electrons, negative charge is compensated by cations, of which the most ubiquitous is H+. Photocharging of semiconductors was studied since 1980th both from fundamental perspective and application – as source of electrons and protons for reduction of organic compounds in dark and solar-to-electric energy conversion. In this review, experimental data collected over 40 years of research is summarized and quantified. Maximum specific concentration of electrons stored in 1 gram of a semiconductor (δmax, mol[e‒] g-1), maximum average number of electrons stored per semiconductor particle (<n max>), initial rate of photocharging (R PC, mol[e‒] g-1 s-1) and initial rate of discharging (R DC, mol[e‒] g-1 s-1) are calculated for 6 classes of semiconducting materials, Ti-, Zn-, Cd-, In-, W- and carbon nitride-based. Dependence of these parameters on material specific surface area, particle volume and other properties is analyzed and trends are derived. Database of photocharged materials is created at pcmat.mpikg.mpg.de to facilitate development of high-performing materials with photocharging function.1. IntroductionTaming the energy of visible light by means of semiconducting materials to enable desirable chemical reactions has been a central research topic of many generations of researchers since the middle of the 20th century. Today the scope of applications is enormous. In the context of synthesis of useful molecules rather than degradation of pollutants, semiconductors (SCs) are considered as primary photocatalysts in large-scale full water splitting under outdoor sun light. On smaller laboratory scale semiconductors are actively studied in synthesis of fine organic molecules under illumination with artificial light generated by LEDs or other light sources.,, Regardless of the scale and the reaction they mediate, from a very general standpoint, photocatalysts enable flow of electron from one reagent to another via photoinduced electron transfer (PET) as schematically shown inFigure 1 .