Experimental evidence of boron induced charged defects in amorphous silicon materials

We present an experimental proof of the existence of charged defects relate d to boron diffusion at the pi interface of single junction amorphous silic on solar cells. Two different test devices were manufactured substituting t he intrinsic absorber layer of a standard p-i-n structure with a boron ligh tly doped layer or a microcompensated region. Presence of trap states lying around 0.3-0.4 eV above the valence band was demonstrated through spectral photocapacitance response under medium infrared radiation and through capa citance versus frequency measurements that show the typical response of tra pping kinetics process. Differences in the experimental results between our test devices and standard p-i-n solar cells show that boron atoms are the main cause of charged defect formation. (C) 1999 Elsevier Science S.A. All rights reserved.