若干物理现象课件

光对材料作用：若干物理现象

ThePhotoelectricEffectIfabeamoflightispointedatthenegativeendofapairofchargedplates,acurrentflowismeasured.Acurrentissimplyaflowofelectronsinametal,suchasawire.Thus,thebeamoflightmustbeliberatingelectronsfromonemetalplate,whichareattractedtotheotherplatebyelectrostaticforces.Thisresultsinacurrentflow.

PhotoelectricEffectEinsteinsuccessfulexplainedthephotoelectriceffectwithinthecontextofthenewphysicsofthetime,quantumphysics.PhotoelectricEffectEnergyofphoton=Energyneededtoremoveanelectron+Kineticenergyoftheemittedelectron

hf=hfo+1/2mv2=ø+Ekh-Planck'sconstant

f0-thresholdfrequencyforthephotoelectriceffecttooccur

ø-workfunction,orminimumenergyrequiredtoremoveelectronfromatomicbinding

Ek-maximumkineticenergyobserved

PhotoelectricSensorsphotomultipliertubes(PMTs)PHOTOVOLTAGEEFFECTHowequilibriumisattainedbetweentwosurfaceswhentheyareplacedinexternalelectricalcontact.PHOTOVOLTAGEEFFECTThesurfacefermi-levelofthesemiconductorshiftsduringillumination.Inthiscasethesemiconductorisapnjunctionandweobtaintheopencircuitvoltage.PHOTOVOLTAGEEFFECTTheoxideand/orsemiconductor-oxideinterfacechargesupduringillumination.Thisaltersthethresholdvoltageasmeasuredbytheprobe.Thesechangescanbequitelarge:upto0.5V.Thesemiconductorinterfacecanbeverysensitivetoevenlowlevelsofilluminationofevenafewlux.SolarCellSolarCellNaturalDye-SensitizedNanocrystallineSolarCellPhotoinducedelectronsPhotosensitiveVaristor

PhotocatalysisPhotocatalysisPhotocatalysis1TiO2+2hν2e-+2h+H2O+2h+

2H++½

O2+

TiO22e-+

2H+

H2淨反應：

H2O+2hνH2+½

O2PhotocatalysisPhotoinducedchargetransferPhotoinducedphasetransitionPhotoinduced

Desorption

PhotoinducedDesorptionPhotochromicsPhotochromicsinLC讨论课安排1、光学玻璃（王盼晓，岳跃平）

玻璃的结构与光学性质；光纤材料及其制备；光波导及其制备；光敏玻璃及其制备。2、光学晶体（殷海波，张剑）

晶体光学性质；激光晶体；非线性光学晶体；光折变晶体；声光晶体；闪烁晶体；光学晶体的制备。

3、有机（高分子）光电材料（姜明，王立晟）

有机物的光学性质；有机光敏材料；有机电致发光材料；有机非线性光学材料；有机光导材料；有机光学材料的制备。4、光学陶瓷（蒋方丹，王婷）陶瓷的光学性质；透明光学陶瓷及其制备；无机发光材料及其制备；多孔太阳能电池材料及其制备。