Spin dependent photoinduced absorption in a-Si:H

We have studied photoexcitation dynamics in undoped a-Si:H from 80 K to 300 K by the techniques of photoluminescence (PL), photoinduced absorption (PA) and their respective versions of optically detected magnetic resonance, namely PLDMR and PADMR. Both PL and PA spectra are composed of low and high energy bands, respectively. Using their respective temperature dependences we correlate the low energy PA band (~0.4 eV) to the high energy PL band (~1.3 eV) and the high energy PA band (~ 1 eV) to the low energy PL band (~0.8 eV). We also found that the PADMR spectrum is composed of three main contributions: a narrow resonance at g ~ 2 (FWHM = 15 G), a broad resonance at g ~ 2 (160 G) and a narrow asymmetric resonance at g ~ 4 (20 G). By measuring their photon energy spectrum we found that the g ~ 4 and the broad g ~ 2 resonances are correlated with each other and therefore are due to trapped electron-hole pairs in the triplet spin configuration.