The mostimportantlimitationfortheefficiency ofphotovoltaicenergyconversionisrelatedtothe
mismatch betweenthebroadbandcharacterofthesolarradiationandthespectralsensitivityofsolar
cells. Largelossesappearatbothsidesofthesolarspectrum.Low-energyphotonsarenotabsorbedand
escape conversion,whereashigh-energyphotonscanonlybeutilizedpartially.Here,wediscusshowthe
loss relatedtolow-energyphotonscanbereducedbyspectralconversion,makinguseofactivelayersof
Si nanocrystalsinanSiO2 matrix. Asapossiblesolution,weconsidergenerationofhotcarriersupon
sequentialintrabandabsorptionoftwoormorelow-energyphotonsandpresentexperimentaldatain
support ofthis.Configurations areproposedinwhichefficient spectralconversioncouldbeachieved,
and theirfeasibilitiesarediscussed.WealsoaddressthefastemissionfromEr3þ ions, purposefully
introduced intotheactivelayer,whichcanbeusedtotracethesuccessfulgenerationofhotcarriers,and
in thatwayservetoevaluatespecific excitationschemes.