As there is the process of transformation of the radiant energy to electric
Concentration and energy of free charge carriers in semiconductors can increase not only when heating, but also under the influence of the radiant energy (light, infrared radiation).
The conductivity of semiconductors caused by action on them the radiant energy is called photoconductivity (the internal fotoyoeffekt). The phenomenon of photoconductivity is the cornerstone of action of group of the electronics called by photoresistance.
Fig. 1 explains action
barrier-film firm photo cell (valve photo cell) in the photogenerating mode.
In the valve photo cell the contact of two poluyoprovodnik, one of whom possesses electronic электропроводностью, and another — hole is made. Thanks to electron diffusion and holes through n - р - transition in mutually opposite directions is formed contact potential difference of UK. If poluprovodyonik are lit, in them due to absorption of light energy nonbasic svoyobodny charge carriers — electrons in the r-semiconductor and holes in the n-semiconductor are formed. These electrons and holes under the influence of the elektricheyosky field, in turn, go through п - р - transition: holes — in the hole semiconductor, and electrons — in electronic. Publicizing of contact leads to the disbalance of majority carriers of the charge as a result of which the potenyotsialny barrier in contact decreases, and new equilibrium state at its smaller value, equal UKC is established.
The difference of potential hills in contact of semiconductors in the dark and lit states is called photo-electromotive force,
Ec = UK - UK.c.
Photo э. of page of subjects is more, than the poluprovodyonik is lit more intensively. After connection of semiconductors there is the circuit current, and proyoiskhodit transformation of the radiant energy to electric.Top