非発光再結合検出による量子ナノ構造太陽電池材料評価(<特集>ナノ・ヘテロ構造を利用した太陽電池)

抄録

Inserting quantum wells (QWs) into GaAs p-i-n solar cells could be a potential solution for the beyond the Shockley-Queisser limit. This is because the QWs can extend the absorption region and enhance the short-circuit current. However, they function as the recombination center leading to degradation in open-circuit voltage. We then evaluate the carrier behaviors by detecting the non-radiative recombination utilizing the piezoelectric photothermal (PPT) technique. The PPT spectra were clearly decomposed into excitonic and inter-subband transitions. From the temperature dependencies of radiative and nonradiative recombination and carrier escape from the well, we estimated the activation energies for non-radiative recombination and thermally carrier escape. The usefulness of the PPT methodology for investigating the QWs-embedded solar cells was clearly demonstrated.