Aspects of Surface Conditioning for High-Efficient Hetero-Junction Silicon Solar Cells

Abstract

As a high-efficiency silicon solar cell concept amorphous silicon/crystalline silicon (a-Si:H(n,p)/c-Si (p,n)) hetero-junction solar cells are of great scientific interest [1, . The a-Si:H emitter is deposited by plasma-enhanced chemical vapor deposition (PECVD). The biggest challenge is to avoid recombination at the a-Si:H(i)/c-Si interface where the p-n junction is located. A clean, smooth, hydrogen terminated c-Si surface is supposed to be mandatory for a high passivation quality of the deposited layer [3, 4]. It is well established that treatment in dilute hydrofluoric acid (dHF) solution (1-10%) produces a hydrogen-terminated, clean Si surface [e.g. 5, 6, 7]. H-termination is supposed to rise with increasing etch time [8]. Whereas prolonged rinsing after the etch step leads to a formation of OH-groups at the surface [8]. Because of the high sensitivity of the a-Si:H(i)/c-Si interface the influence of prolonged etching in dHF (1%) as well as prolonged rinsing in deionized water (DI water) on the passivation quality of the deposited a-Si:H(i) layer has to be carefully studied. Also the possibility of decreased hydrophobicity and a possible iron recontamination from the HF has been taken into account.