Steffens, S.; Becker, C.; Zollondz, J.-H.; Chowdhury, A.; Slaoui, A.; Lindekugel, S.; Schubert, U.; Evans, R.; Rech, B.: Defect annealing processes for polycrystalline silicon thin-film solar cells. Materials Science and Engineering B 178 (2013), p. 670-675
A variety of defect healing methods was analysed for optimization of poly-Si thin-film solar cells on glass. The films were fabricated by solid phase crystallization of amorphous silicon deposited either by plasma enhanced chemical vapour deposition (PECVD) or by electron-beam evaporation (EBE). Three different rapid thermal processing (RTP) set-ups were compared: A conventional rapid thermal annealing oven, a dual wavelength laser annealing system and a movable two sided halogen lamp oven. The two latter processes utilize focussed energy input reducing the thermal load introduced into the glass substrates and thus leading to less deformation and impurity diffusion. Analysis of the structural and electrical properties of the poly-Si thin films was performed by SunsVOC measurements and Raman spectroscopy. 1cm² cells were prepared for a selection of samples and characterized by I-V-measurements. The poly-Si material quality could be extremely enhanced, increasing the open circuit voltages from about 100 mV (EBE) and 170 mV (PECVD) in the untreated case up to 480 mV after processing.