The Effect of Surface Manipulation of Mo Back Contact on Controlling Cu(In,Ga)Se2 (CIGS) Preferred orientation and the Demonstration of Their Effects on Cell Efficiency

Title
The Effect of Surface Manipulation of Mo Back Contact on Controlling Cu(In,Ga)Se2 (CIGS) Preferred orientation and the Demonstration of Their Effects on Cell Efficiency
Authors
윤주헌성태연김종근윤관희김원목박종극백영준정증현
Keywords
CIGS; Back Contact; Preferred Orientation; Efficiency
Issue Date
2011-04
Publisher
Materials Research Society
Abstract
The effect of surface density of Molybdenum (Mo) back contact on controlling the preferred orientation of Cu(In,Ga)Se2 (CIGS) films was investigated using two different layered-Mo structures: one is the relatively less dense and thin Mo layer deposited on very dense and thick Mo layer and the other is a single layer of thick dense Mo. The (112) texture typically shown in CIGS films on a single dense Mo layer was changed significantly into (220)/(204) texture of CIGS on the layered Mo (with less dense top Mo layer). It is strong evidence showing that surface density of Mo back contact determines the CIGS preferred orientation. Herein we suggest a novel Mo layered structure as a back contact comprising of the less dense thin layer on bi-layer. The top layer is for controlling the CIGS preferred orientation and the bottom bi-layer for guaranteeing the thermal stability of highly conductive back contact during high-temperature CIGS process. Using such a more practical structure as described above, the effect of CIGS preferred orientation on cell performances, (at least excluding other effect such as Mo degradation) could be investigated fairly by just changing the nature of the top Mo layer. The efficiency of CIGS solar cells made on the layered Mo structures as a function of the deposition pressure of top layer Mo (2~16 mTorr) depends strongly on CIGS (220)/(204) preferred orientation: Open-circuit voltage (Voc) was increased with increasing (220)/(204) texture. It was attributed to the decrease of ideality factor (n) with CIGS (220)/(204) texture. In addition, the slightly decrease of series resistance (Rs) and optical band gap was observed with increasing CIGS (220)/(204) preferred orientation.
URI
http://pubs.kist.re.kr/handle/201004/39836
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KIST Publication > Conference Paper
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