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ENERGY PHOTOVOLTAICS

# April 11, 2003

Dr. Harin Ullal, Technical Monitor

National Renewable Energy Laboratory

1617 Cole Boulevard

Golden, CO 80401

Dear Harin,

Enclosed please find the fifth quarterly report for EPV's cost-shared
subcontract RDJ-2-30630-21 **Advanced CIGS Photovoltaic Technology**
awarded under the Thin Film Partnership Program. The nominal period
covered by the report is 11/15/02 - 2/28/02. Note that under
modification no. 1, Phase I was extended and formally ended on 2/28/02.

During this period, the company and its founder Zoltan Kiss, parted
ways. The EPV CIGS team was then **re-organized** to promote better
interaction and manning of critical operations. The CIGS research group
and the CIGS process team were merged into one CIGS group within the R&D
Department headed by Alan Delahoy. The group leader is Leon Chen.

Although outside of this reporting period, we are nevertheless pleased
to announce a new addition to the group -- **Dr. Baosheng Sang**.
Baosheng started 4/7/03. He will work on CIGS recipe development in the
Zeus and on CIGS patterning, including laser patterning, and possibly
oversee large area ZnO optimization. He will also become involved with
the reactive environment sputtering program with a view to applying this
technique to the CIGS program. Baosheng came to us as a Post-Doctoral
Researcher at the University of Delaware working on co-evaporated CIGS
and CBD ZnS. Previously he worked with Dr. Kushiya at Showa Shell on
CIGSS modules, ZnO:Ga, ZnO:B, and sputtering. His Ph.D. is from the
Tokyo Institute of Technology, where he worked on ALD ZnO and CIGS.

This report deals with the following areas of activity:

1)  Re-establishment of team strategy

2)  Investigation of Se reproducibility in Zeus

3)  Assistant experiments conducted in Hercules

4)  CdS process for large size substrates

5)  ZnO in in-line sputtering system and in HC chamber

6)  Alternative junctions

> 7\) Plans for next quarter
>
> 8\) Corporate update

1)  **Re-establishment of team strategy**

A vigorous discussion and review of our existing CIGS program was held
in conjunction with reorganization of the CIGS team. A consensus was
reached that we should focus our research and process efforts on the
following three aspects:

-   Large size module process

In the past two quarters we have made great progress in performance both
at the device level and at the mini-module level with a **hybrid CIGS
process** involving Cu sputtering. It proved that we could make 9%
aperture area mini-modules (35 cm^2^) based on 13.5% device efficiency.
Of the 35% efficiency drop (from 13.5% device to 9% mini-module), around
18% is due to FF loss from ZnO front contact and interconnection, 12%
due to Jsc loss from dead area, and another 5% is due to Voc loss and
non-uniformity. We concluded that we should switch our main focus from
device level and mini-module to large area modules, bearing in mind that
there is still room for improvement for the device and mini-module. It
is believed that we should be able to make a large area CIGS module (for
the time being 1 square foot in size) with 8% efficiency during the next
two quarters. A module layout and design have been completed and some
plates with Mo laser scribe lines are checked and tested.

-   Component readiness

Two different sets of process equipment are used to produce mini-modules
and large area modules. The equipment is listed in Table I. Also listed
in Table I are difficulty assessment/main problems and requirement for
every component in scale-up.

Table I. Equipment assessment regarding near-term production of 8%
1ft^2^ module

+--------+----------+------------+----------------+-------------------+
| **Main | **E      | *          | **Difficulty   | **Requirement     |
| pro    | quipment | *Equipment | assessment**   | for**             |
| cess** | for      | for        |                |                   |
|        | mini-    | large-area | **and main     | **scale-up**      |
|        | module** | module**   | problems**     |                   |
+--------+----------+------------+----------------+-------------------+
| Mo     | In-line  | In-line    | No problem     | done              |
|        | sputter  | sputter    |                |                   |
+--------+----------+------------+----------------+-------------------+
| Mo     | Laser    | Laser      | No problem     | done              |
| scribe |          |            |                |                   |
+--------+----------+------------+----------------+-------------------+
| CIGS   | Hercules | Zeus       | Main           | 13% level CIGS    |
|        |          |            | difficulty:    | process with less |
|        |          |            | low collection | than 5%           |
|        |          |            | and            | non-uniformity    |
|        |          |            | non-r          | and good          |
|        |          |            | eproducibility | reproducibility   |
+--------+----------+------------+----------------+-------------------+
| CdS    | Beaker   | Tank       | Straight       | Need to           |
|        |          |            | forward        | demonstrate tank  |
|        |          | (under     |                | process as good   |
|        |          | test)      |                | as beaker         |
+--------+----------+------------+----------------+-------------------+
| ZnO    | Airco    | In-line    | Heaters are    | Mid-freq. to      |
|        |          | sputter    | needed for     | produce the same  |
|        | (RF,     |            | improving ZnO  | quality ZnO as RF |
|        | ceramic  | (          | performance    | after             |
|        | target)  | mid-freq., |                | installation of   |
|        |          | ceramic)   |                | heaters           |
+--------+----------+------------+----------------+-------------------+
| CI     | Manual,  | X-Y table, | Main           | Dead space should |
| GS/ZnO | me       |            | difficulties:  | be no larger than |
| s      | chanical | mechanical | alignment and  | that in           |
| cratch |          |            |                | mini-module       |
|        |          |            | scratch        |                   |
|        |          |            | pressure       |                   |
+--------+----------+------------+----------------+-------------------+

As shown in Table I, a 13 % device level CIGS process over one square
foot with 5 % non-uniformity is required from the Zeus system in order
to produce 8 % one square foot modules if all the rest of the components
perform as well as those in the mini-module line. To achieve this goal,
we have to have all components ready. Based on such a philosophy, we
decided to pay great attention to testing and checking each component
separately and making sure all components are working properly before
integrating all of them into a module.

-   Reproducibility and Process control

CIGS films deposited in our Zeus system have often shown
non-reproducible behavior. That is one of the main reasons why we could
not get consistently good results from Zeus. In the past, the Zeus
manager was reluctant to spend his time on basic film studies for a
single source or two components since they are only tests rather than
'real' runs. We have now concluded that performance improvement,
supposed to have resulted from change of process recipe, might well have
been noise from a not-well-controlled system. Furthermore, the root
causes of non-reproducibility remained obscure. The new team decided
early on to bite the bullet to spend plenty of time addressing the
reproducibility of individual sources. We started with Se deposition,
which is described in section 2.

2)  **Investigation of Se reproducibility in Zeus**

Se evaporation is the easiest deposition among In, Cu, Ga and Se because
it only needs a source temperature of about 310 °C due to its high vapor
pressure. The substrate was kept at room temperature during evaporation
to assure condensation. In this investigation, we tried to answer the
following questions:

a)  How good or bad is the reproducibility of our Se evaporation in the
    Zeus?

b)  What causes it if reproducibility is bad?

c)  Which is the better control parameter for Se (and others)
    evaporation: crucible temperature, or crystal monitor?

d)  What is the safety zone of Se deposition rate in deposition of
    different compositions to prevent deposition of InSe rather than
    In~2~Se~3~ and to prevent etch-back?

e)  What is our tolerance of Se non-reproducibility and non-uniformity
    since Se would be self-regulated in two- or three-component films
    such as In~2~Se~3~, Ga~2~Se~3~, and (In,Ga)~2~ Se~3~ ?

In this section, we will discuss a) and b), while c), d) and e) will be
reported in section 3.

Four sequential Se evaporation runs in test 1 were made on the same day.
All test conditions and results are listed in Table II.

**Table II. Successive Se runs in Zeus**

+------------+-----------+------------+------------+-----------------+
| **Se       | **D       | **Average  | **Standard | **Time starting |
| tem        | eposition | t          | deviation  | from initial    |
| perature** | duration  | hickness** | of         | heat-up of Se   |
|            | (min.)**  |            | thickness  | crucible        |
| **(C)**    |           | **(A)**    | (A)**      | (hrs)**         |
+------------+-----------+------------+------------+-----------------+
| 300        | 10        | Very thin  |            | 2               |
+------------+-----------+------------+------------+-----------------+
| 310        | 10        | 1812       | 251        | 4               |
+------------+-----------+------------+------------+-----------------+
| 320        | 10        | 3649       | 519        | 6               |
+------------+-----------+------------+------------+-----------------+
| 300        | 10        | 2500       | 256        | 8               |
+------------+-----------+------------+------------+-----------------+

The data suggested that the massive Se crucible and its oven need a very
long time (\> 4 hrs after switch-on) to heat up and stabilize. We
thought this might represent the main factor responsible for
non-reproducibility until we discovered that the crystal thickness
monitor exhibited a periodic signal indicating that the Se flux changed
periodically with a period of about 10 minutes although the Se crucible
temperature was 'constant'. The ratio of peak signal to valley signal
was as high as a factor of 2. Such a large ratio precluded fluctuation
of Se crucible temperature because the vapor pressure of Se doubles only
if Se crucible temperature fluctuation is as high as 20 °C, which is
definitely not the case in the Zeus system. After having carefully
observed both the Se crucible and Se oven temperature, we were surprised
to notice that the Se oven temperature during the power-off period of
the heater dropped much faster than the crucible temperature due to its
smaller thermal mass until eventually the oven temperature is even lower
than that of crucible. This temperature reverse permits Se vapor to
condense in the oven, which drastically reduces the Se flux from the
source. During the power-on period of the heater, the oven temperature
increases much faster than that of the crucible due to its smaller
thermal mass so that Se is totally vaporized again in the oven as soon
as the oven temperature catch up with the crucible temperature. That the
condensation causes the periodic behavior is our working hypothesis for
the time being. In addition, we found that our home-made Se crucible
temperature controller (computer) has not controlled to a degree that we
are satisfied with yet. We are planning to use a commercial EUROTHERM
temperature controller (as used by Hercules) to control Zeus' sources to
see if the controllability can be improved.

Meanwhile, we conducted the second set of Se deposition reproducibility
tests after the source material was refilled. In order to minimize
non-reproducibility introduced by the periodic behavior, we operated in
such a way that all Se depositions started at the same instant (or
phase) of the period for three Se repeat runs. As expected,
reproducibility for these three runs was improved significantly, since
the film thickness is a time integration of the Se flux. Listed in Table
III are the test data.

Table III. Repeat Se runs in Zeus

+------------+------------+------------+-----------+-----------------+
| **Se       | **         | **Average  | *         | **Time starting |
| tem        | Deposition | of         | *Standard | from initial    |
| perature** | duration   | t          | deviation | heat-up of Se   |
|            | (min.)**   | hickness** | of        | crucible        |
| **(C)**    |            |            | thickness | (hrs)**         |
|            |            | **(A)**    | (A)**     |                 |
+------------+------------+------------+-----------+-----------------+
| 320        | 10         | 7577       | 1032      | 3               |
+------------+------------+------------+-----------+-----------------+
| 320        | 10         | 7460       | 1136      | 5               |
+------------+------------+------------+-----------+-----------------+
| 320        | 10         | 7280       | 1062      | 7               |
+------------+------------+------------+-----------+-----------------+

The data also showed that three hours warm-up time is sufficient. In
addition, it is noted that the Se deposition rate in the Zeus system is
about 12-13 A/s at 320 °C, which is on the low side of the range 15-20
A/s that we are now seeking.

3)  **Assistant experiments conducted in Hercules**

As described in section 1, we are focusing on improvement of large area
module processing. Therefore, we determined that the primary role for
the Hercules system is assistance of Zeus in the areas of recipe
development and transfer.

In this quarter, we conducted Se evaporation tests in Hercules as well.
The first set of experiments was to test use of a quartz crystal film
monitor as a control parameter for Se evaporation rather than
temperature (question c in Sec. 2). There are several drawbacks to using
temperature as the control parameter:

-   The measured temperature of the Se crucible is not uniquely
    correlated to deposition rate. Other factors such as system
    pressure, which is function of substrate temperature and other
    source (In and Ga) temperatures, also affect Se rate due to change
    of mean free path. Also, the temperature differential between the
    thermocouple and the surface of the melt need not be constant. This
    differential can depend on the heat flux and on the degree of
    thermal contact between the thermocouple and crucible (this may
    change after refilling the crucible). Thus, even if the temperature
    reading is constant, the melt temperature may be different, and Se
    vapor pressure is exponentially dependent on temperature.

-   Film thickness is also a function of warm-up time as we mentioned in
    Sec.2.

In principle, there are no such problems when a crystal monitor is used
for control. Listed in Table IV are data from two repeated Se runs
conducted in the Hercules system using a crystal monitor.

Table IV. Repeat Se runs in Hercules

+------------+------------------+------------------+------------------+
| **Run ID** | **Monitor        | **Actual film    | **Thickness      |
|            | thickness (kA)** | thickness**      | ratio (film to   |
|            |                  |                  | monitor)**       |
|            |                  | **(average,      |                  |
|            |                  | kA)**            |                  |
+------------+------------------+------------------+------------------+
| H167       | 21.18            | 27.39            | 1.29             |
+------------+------------------+------------------+------------------+
| H168       | 21.35            | 26.07            | 1.22             |
+------------+------------------+------------------+------------------+

The data showed that the reproducibility of Se film thickness in the two
runs is within 6 % using the crystal monitor to control the evaporation,
which is equivalent to a reproducibility of about 1 °C in Se crucible
temperature were this used to control the process. We are planning to do
a similar test in the Zeus next quarter to establish a solid foundation
for process control parameters.

The second set of experiments, addressing questions d) and e) in Sec.2,
is to find a safety zone for Se rate. We know that the main compound in
the film from two-element evaporation (Se and In) would be InSe rather
than In~2~Se~3~ at low Se rate, which defines the Se rate minimum
boundary. The mole ratio of Se/In in the film measured by ICP is chosen
as an indicator to distinguish InSe (the ratio is close to 1) and
In~2~Se~3~ (the ratio is close to 1.5). On the other hand, elements
other than Se, like In, might be etched off at high Se rate, which
defines its maximum boundary. The total thickness of the film is chosen
as an indicator to check if there is any In etched off. In view of a Se
deposition rate of about 15 A/s in our normal process, we investigated a
Se rate window over a factor of two from 10 A/s to 20 A/s with 15 A/s in
the middle to test the ratio of Se/In and total thickness of the film.
Listed in Table V are the test conditions and results.

Table V

+------+------+---------+--------+--------+--------+--------+--------+
| *    | **T~ | **Se    | **Mass | *      |        | *      |        |
| *Run | subs | rate**  | of In  | *Ratio |        | *Total |        |
| ID** | trat |         | (g)**  | of     |        | thi    |        |
|      | e~** | **      |        | S      |        | ckness |        |
|      |      | (A/s)** |        | e/In** |        | (A)**  |        |
|      | **(° |         |        |        |        |        |        |
|      | C)** |         |        |        |        |        |        |
+------+------+---------+--------+--------+--------+--------+--------+
|      |      |         |        | **ave  | **std  | **ave  | **std  |
|      |      |         |        | rage** | dev**  | rage** | dev**  |
+------+------+---------+--------+--------+--------+--------+--------+
| H166 | 350  | 10 (to  | 1.5922 | 1.46   | 0.028  | 9,006  | 520    |
|      |      | 16)     |        |        |        |        |        |
+------+------+---------+--------+--------+--------+--------+--------+
| H169 | 350  | 21 (to  | 1.5944 | 1.47   | 0.027  | 9,257  | 692    |
|      |      | 33)     |        |        |        |        |        |
+------+------+---------+--------+--------+--------+--------+--------+

It becomes clear from the data in Table V, that neither the ratio of
Se/In in the film nor the total thickness of the film have any
significant change at the two ends (10 A/s and 21 A/s) of the window
range, which gives our Se flux safety zone. We are not interested to go
further to find out 'the upper boundary of Se rate' since it is always a
desire to lower material flux in manufacturing operations. The results
also relax our requirements of reproducibility and uniformity for Se
flux in large area module processing since thickness and composition of
the In~2~Se~3~ film are almost totally dominated by In rate (here, In
mass) as long as Se is in its safety zone due to its self-regulating
mechanism. This is the answer to question e) in Sec.2. We are planning
to do the same test at an increased substrate temperature to 500 °C (the
temperature for the third stage) instead of 350 °C (the temperature for
the first stage) to see if the same conclusion holds.

In the above experiments, we also found that the Se sticking coefficient
is larger on Mo than on plain glass.

4)  **CdS process for large size substrates**

The goal we set for the CdS task in this period was to achieve a good
process for 1 ft^2^ substrates. We took our device and mini-module CdS
process as a reference to compare with. Our small area CdS process has
yielded 13.5% device performance using EPV CIGS films. Recently, we used
a CIGS sample obtained from NREL to further check our non-CIGS
processing including CdS. Over 15% device efficiency (Voc 641 mV, FF
74.5% and Jsc 32.4 mA/cm^2^) without AR coating and contact finger was
reached, which gives us confidence in our reference process. We also
noted that the NREL material showed a much smaller light soaking effect
and post-CIGS treatment improvement than EPV samples do, which might
indicate that CIGS film with sputtered Cu has a different behavior than
CIGS with evaporated Cu. Listed in Table VI are some hardware
differences between our small and large area CdS process.

Table VI. Hardware differences for small and large area CBD CdS

  ---------- ------------- ------------- ------------ --------------- -------------
  **Area**   **Reactor**   **Material of **Heater     **Temperature   **Stirrer**
                           container**   source**     controller**    

  Small      Beaker        Glass         Hot plate    No              Magnetic

  Large      Tank          Stainless     Outside tank Yes             Electric
                           steel         wall                         
  ---------- ------------- ------------- ------------ --------------- -------------

The experimental results reported below were generated using
simultaneously two reactor vessels i.e. 1 Liter glass beaker versus a 9
Liter stainless steel rectangular tank capable of holding 12" by 12"
substrates. The composition of a typical chemical bath is: CdSO~4~
0.0015M; NH~4~OH 2.25 M; SC(NH~2~)~2~ 0.15M. While using simultaneously
both beaker and tank, we carried out CdS deposition reactions in the
temperature range of 50-60 °C on 2" by 4" CIGS films cut from a large
plate made in the Zeus system. At present we are continuing these
studies, however, this work has shown that while device quality CdS film
could be grown in a beaker as low as 50 °C, the comparable quality CdS
film from the stainless steel tank required an elevated temperature
close to 60 °C. We report some of our results in Table VII, where the
product of V~oc~ and FF for both process vessels is compared.

Table VII. V~oc~.FF product for various CBD CdS

  ----------- ------------ ----------------- ----------- ----------- -----------
  **Sample    **Vessel**   **Temperature**   **V~oc~     **FF (%)**  **V~oc~ x
  ID**                                       (mV)**                  FF**

  Z1543-M3 C3 Beaker       53 C              541.9       58.8        31864

  Z1543-N3 A5 Beaker       53 C              523.6       50.76       26578

  Z1543-N1 C3 Tank         53 C              513         52.72       27045

  Z1543-M1 C3 Tank         53 C              533.7       52.54       28041

  Z1543-20 B5 Beaker       54 C              524.1       60.31       31608

  Z1543-22 C3 Beaker       54 C              499.4       52.93       26433

  Z1543-21 A2 Tank         58 C              489.6       58.38       28583

  Z1543-23 B5 Tank         58 C              564.8       54.72       30906
  ----------- ------------ ----------------- ----------- ----------- -----------

The preliminary data in Table VII above show no statistically
significant difference for our CdS CBD process in both vessels. More
experiments are planned in the next quarter to finally validate the CdS
process for large area modules. A new design for a circulated water bath
to improve the uniformity of large area CdS CBD is on the way.

5)  **ZnO in in-line sputtering system and in HC chamber**

We have focused on up-grading the in-line sputtering system in this
quarter. Based on an earlier report, the electrical and optical
performance of ZnO deposited with a DC pulsed power supply are
significantly improved by heating the substrate to about 180 °C. A
design for constructing and installing two large area heaters has been
completed and purchase orders will be placed soon.

Under our NIST ATP award, we have been making doped ZnO by hollow
cathode (HC) sputtering. We have started to use this material on CIGS
prepared under the TFPPP subcontract.

**6) Alternative junctions**

We continue to pursue various methods and sequences for treatments,
buffer layers, and TCO deposition in an effort to unravel the various
elements of junction formation. Junctions using ZnIn~2~Se~4~ (ZIS) as a
buffer layer and bufferless (CIGS/ZnO) junctions are of particular
interest. Some results obtained in this quarter are shown in Table VIII.

Modifications to the boats and method of substrate heating in the
evaporator used for buffer layers necessitated a re-optimization of ZIS
deposition parameters. The first two lines of Table VIII compare results
obtained with two different thicknesses of ZIS. The thickness was
changed by changing the mass of ZIS loaded. It should be mentioned that,
in Table VIII, "standard ZIS" represents a previously-optimized bi-layer
recipe, while "ZIS" represents a single layer.

The next four entries represent fine tuning of the substrate temperature
T~s~ for ZIS evaporation. An optimal T~s~ of 185 °C was determined (6.4%
efficiency with EPV CIGS).

We were fortunate in being able to secure from Kannan Ramanathan a 3" x
3" sample of NREL CIGS for comparative studies. It can be seen from a
later entry in the Table that a best cell efficiency of 15.5% was
achieved using EPV's recently optimized CBD CdS. (The I-V curve for this
cell is shown after Table VIII.) Surprisingly, the standard ZIS recipe
only gave 1.8%. This appears to confirm that junction recipes developed
for one type of absorber do not necessarily transfer well to a different
absorber. Evaporation of a thin layer of Cd onto the CIGS before
deposition of the ZIS gave 3.7%. If ZIS was followed by a thin CdS dip,
11.8% was attained. With CBD CdS (and no ZIS) 12.7% was achieved. (This
latter cell was processed using a different CBD set up than that used
for the 15.5% cell.)

With non-standard deposition of the ZnO onto standard ZIS (instead of RF
magnetron), 6.2% was achieved on the NREL material, rising to 8.5% after
light soaking. For a bufferless cell, 12.7% was achieved, rising to
13.3% after light soaking. This is a very nice result, as it is not too
far away from the 15% range obtained with conventional processing (CBD
CdS). The lack of CdS absorption is reflected in the high J~sc~ of 35.6
mA/cm^2^ obtained by integrating under the QE curve.

For a bufferless cell on EPV CIGS, 4.1% was achieved, compared to 9.6%
with CBD CdS.

The final set of four entries suggested that EPV's pre-treatment step
enhanced efficiency of devices using HC ZnO, and that ZIS was preferable
to standard ZIS. These results are the opposite of what was found in
earlier studies using RF ZnO.

Table VIII. Various buffer layer experiments

+--------+--------------------+-----------+------+---+------+---+---+
| **     | **Buffer (EPV)**   | **con     | **Z  | * | *    | * | * |
| CIGS** |                    | ditions** | nO** | * | *J~s | * | * |
|        |                    |           |      | V | c~** | F | η |
|        |                    |           |      | ~ |      | F | * |
|        |                    |           |      | o | **mA | * | * |
|        |                    |           |      | c | /cm^ | * |   |
|        |                    |           |      | ~ | 2^** |   | * |
|        |                    |           |      | * |      | * | * |
|        |                    |           |      | * |      | * | % |
|        |                    |           |      |   |      | % | * |
|        |                    |           |      | * |      | * | * |
|        |                    |           |      | * |      | * |   |
|        |                    |           |      | m |      |   |   |
|        |                    |           |      | V |      |   |   |
|        |                    |           |      | * |      |   |   |
|        |                    |           |      | * |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| EPV    | Standard ZIS       | 25mg      | n    | 3 | 29.2 | 3 | 3 |
| H159   | (180°C)            |           | (RF) | 8 |      | 4 | . |
|        |                    |           |      | 4 |      | . | 9 |
|        |                    |           |      |   |      | 7 | 0 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | 15mg      |      | 3 | 31.1 | 4 | 4 |
|        |                    |           |      | 7 |      | 0 | . |
|        |                    |           |      | 9 |      | . | 8 |
|        |                    |           |      |   |      | 9 | 3 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| EPV    | Standard ZIS       | 165°C     | n    | 3 | 30.8 | 4 | 4 |
| H159   | (15mg)             |           | (RF) | 5 |      | 2 | . |
|        |                    |           |      | 5 |      | . | 6 |
|        |                    |           |      |   |      | 1 | 0 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | 175°C     |      | 3 | 29.2 | 4 | 4 |
|        |                    |           |      | 6 |      | 6 | . |
|        |                    |           |      | 9 |      | . | 9 |
|        |                    |           |      |   |      | 3 | 9 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | 185°C     |      | 4 | 27.9 | 5 | 6 |
|        |                    |           |      | 0 |      | 6 | . |
|        |                    |           |      | 5 |      | . | 3 |
|        |                    |           |      |   |      | 3 | 7 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | 195°C     |      | 4 | 28.4 | 5 | 6 |
|        |                    |           |      | 0 |      | 2 | . |
|        |                    |           |      | 2 |      | . | 0 |
|        |                    |           |      |   |      | 5 | 1 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| NREL   | Standard ZIS       | 185°C     | n    | 4 | 15.5 | 2 | 1 |
| S2061  |                    |           | (RF) | 8 |      | 4 | . |
|        |                    |           |      | 0 |      | . | 8 |
|        |                    |           |      |   |      | 6 | 3 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Evap Cd / Standard | 185°C     |      | 5 | 29.7 | 2 | 3 |
|        | ZIS                |           |      | 4 |      | 3 | . |
|        |                    |           |      | 2 |      | . | 7 |
|        |                    |           |      |   |      | 2 | 3 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Standard ZIS /     | 185°C     |      | 5 | 31.5 | 6 | 1 |
|        | thin CBD CdS       |           |      | 5 |      | 7 | 1 |
|        |                    |           |      | 2 |      | . | . |
|        |                    |           |      |   |      | 8 | 8 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Pre-treatment /    | \-        |      | 6 | 31.3 | 6 | 1 |
|        | CBD CdS            |           |      | 0 |      | 7 | 2 |
|        |                    |           |      | 6 |      | . | . |
|        |                    |           |      |   |      | 0 | 7 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| NREL   | Standard ZIS       | 185°C     | i-n  | 5 | 34.0 | 3 | 6 |
| S2061  |                    |           | (HC) | 7 |      | 2 | . |
|        |                    |           |      | 1 |      | . | 2 |
|        |                    |           |      |   |      | 0 | 1 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | Light     |      | 5 | 34.0 | 4 | 8 |
|        |                    | soak 21h  |      | 9 |      | 2 | . |
|        |                    |           |      | 3 |      | . | 5 |
|        |                    |           |      |   |      | 3 | 2 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Pre-treatment only | \-        |      | 5 | 35.6 | 6 | 1 |
|        | (no buffer)        |           |      | 6 |      | 3 | 2 |
|        |                    |           |      | 4 |      | . | . |
|        |                    |           |      |   |      | 4 | 7 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    | Light     |      | 5 | 35.6 | 6 | 1 |
|        |                    | soak 21h  |      | 6 |      | 6 | 3 |
|        |                    |           |      | 2 |      | . | . |
|        |                    |           |      |   |      | 3 | 3 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| NREL   | CBD CdS            | Best      | i-n  | 6 | 32.4 | 7 | 1 |
| S2061  |                    | result    | (RF) | 4 |      | 4 | 5 |
|        |                    |           |      | 1 |      | . | . |
|        |                    |           |      |   |      | 5 | 5 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| EPV    | Pre-treatment only | i:120°C   | i-n  | 3 | 33.5 | 3 | 4 |
| H170   | (no buffer)        | 600mT     | (HC) | 6 |      | 3 | . |
|        |                    |           |      | 5 |      | . | 1 |
|        |                    |           |      |   |      | 6 | 1 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Pre-treatment /    | i:120°C   | i-n  | 5 | 28.7 | 6 | 9 |
|        | CBD CdS            | 300mT     | (HC) | 1 |      | 5 | . |
|        |                    |           |      | 0 |      | . | 5 |
|        |                    |           |      |   |      | 5 | 7 |
+--------+--------------------+-----------+------+---+------+---+---+
|        |                    |           |      |   |      |   |   |
+--------+--------------------+-----------+------+---+------+---+---+
| EPV    | Standard ZIS       |           | i-n  | 3 | 20.1 | 1 | 1 |
| H170   |                    |           | (HC) | 7 |      | 8 | . |
|        |                    |           |      | 0 |      | . | 4 |
|        |                    |           |      |   |      | 9 | 0 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Pre-treatment /    |           |      | 4 | 30.3 | 2 | 3 |
|        | standard ZIS       |           |      | 0 |      | 7 | . |
|        |                    |           |      | 5 |      | . | 3 |
|        |                    |           |      |   |      | 2 | 3 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | ZIS                |           |      | 3 | 28.3 | 4 | 4 |
|        |                    |           |      | 6 |      | 5 | . |
|        |                    |           |      | 2 |      | . | 6 |
|        |                    |           |      |   |      | 5 | 7 |
+--------+--------------------+-----------+------+---+------+---+---+
|        | Pre-treatment /    |           |      | 4 | 31.7 | 4 | 6 |
|        | ZIS                |           |      | 2 |      | 8 | . |
|        |                    |           |      | 8 |      | . | 5 |
|        |                    |           |      |   |      | 2 | 6 |
+--------+--------------------+-----------+------+---+------+---+---+

![](media/image2.wmf){width="4.992361111111111in" height="3.56875in"}

7)  **Plans for next quarter**

-   Improve cell and mini-module performance in Hercules.

-   Finish evaluation of Eurotherm temperature controller and find
    short-term and long-term solution in Zeus system. Determine
    reproducibility for single-source and two-source evaporation after
    improving temperature control.

-   Transfer Hercules recipe to Zeus.

-   Validate CdS CBD in large area vessel with new circulating water
    bath.

-   Start to make and test 1 ft^2^ modules.

-   Complete in-line sputtering system up-grade.

-   Conduct exploratory work concerning a) evaporation of certain
    powders; b) two new active materials; c) temperature resistance of
    junctions; d) superstrate devices.

-   Continue alternative buffer layer program.

8)  **Corporate update**

Several shipments of equipment have been made to Tianjin in connection
with the setting up of an IMS, and revenues are being collected in
orderly fashion. Arrangements are being pursued to enable equipment
manufacturing and shipments to Greece. Negotiations are at an advanced
stage for a third IMS.

Sincerely,

# Alan E. Delahoy Leon Chen

# Principal Investigator Senior Scientist