efficient high control by thin films of high quality

(1)

Fabrication of high quality CuInSz thin films by defect control and its application to high efficient solar cells

2001 Takayuki Wttanabe

The chalcopyrite semiconductor CuInSz is an attractive material for high efficient solar cells

because

its band gap

matches

well with the solar spectrum. Up to now, high effiicient solar cells have been fabricated using poisonous KCN process in order to remove CuS phase segregated on Cu-rich CuInSz films because the quality of Cu-poor CuInSz films were not good. The purposes of this study are to establish the fabrication technique of CuInSz thin films without KCN treatment, to clarify the crystallographic and electrical properties of Cu-poor CuInSz films and to fabricate high efficienct solar cells based on the CuInSz films.

CuInSz thin films were

prepared

by sulfurization of Cu-In-S precursor films deposited using reactive spuffering with

HzS gas.

Uniform and smooth CuInSz films were formed by control of S contents in the precursor. Cu-poor CuInSz films with high conductivity were also fabridcated by co-incorporation of Na and O. From the experimental and theoretical results,

a

model of defect structure, which includes

the

complex

Nacu-Os, was proposed.

The generation of donor

defects,

especially divacancy

Vs-cu,

was

suppressed

by co-incorporation of Na

and

O. Therefore, the conductivity for p-type CuInSz thin films were enhanced. This model provides guidelines for the discussion on "sodium effect" for ClS-based solar cells, which is the most important factor to cell efficiency.

It was also demonstrated that co-incorporation of Na

and

O into Cu-poor CuInSz films is essential technique for fabricating high efficient solar cells without KCN treatment. The efficiency of

10.6%o

is extremely higher than that of no-incorporated films (lVo or low). Furthernore,

an

efficient high control by thin films of high quality

Fabrication of high quality CuInSz thin films by defect control and its application to high efficient solar cells

2001 Takayuki Wttanabe

The chalcopyrite semiconductor CuInSz is an attractive material for high efficient solar cells

its band gap

CuInSz thin films were

by sulfurization of Cu-In-S precursor films deposited using reactive spuffering with

Uniform and smooth CuInSz films were formed by control of S contents in the precursor. Cu-poor CuInSz films with high conductivity were also fabridcated by co-incorporation of Na and O. From the experimental and theoretical results,

model of defect structure, which includes

complex

The generation of donor

especially divacancy

was

by co-incorporation of Na

O. Therefore, the conductivity for p-type CuInSz thin films were enhanced. This model provides guidelines for the discussion on "sodium effect" for ClS-based solar cells, which is the most important factor to cell efficiency.

It was also demonstrated that co-incorporation of Na

O into Cu-poor CuInSz films is essential technique for fabricating high efficient solar cells without KCN treatment. The efficiency of

is extremely higher than that of no-incorporated films (lVo or low). Furthernore,

efficiency of ll.2Vo was achieved for Cu(In,Ga)Sz solar cell with graded bandgap structure.

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