# Presentation: 164565

## Simplified Hybrid Process: Application to Normal, Sub-micron, and Light-trapping CIGS Devices 

**  **

**Simplified Hybrid Process: Application to Normal, Sub-micron, and Light-trapping CIGS Devices**** **

** ****CONCLUSIONS**

**Acknowledgements:  **The authors thank R. Saramak, R. Zhang, J. Cambridge, A. Foustotchenko and R. Lyndall of EPV for their contributions.  We are grateful to W. Shafarman for reflectivity, XRD measurement and fabrication of some CIGS devices, and R. To and M. Al-Hassim of NREL for SEM analysis. This work was partially supported by the U.S. DOE under subcontract ZXL-5-44205-05 with NREL, Harin Ullal Technical Monitor.

- EPV CIGS module

** ****During 2005, EPV developed ****a**** simplified ****hybrid process ****for CIGS**** combining sputtering and linear thermal source deposition.  The simplified process has **
**    ****considerably reduced CIGS processing time.  It also proved suitable for production of sub-micron CIGS.**
** ****A device efficiency of ****14.1%**** was achieved at a ****CIGS thickness of 1.3 ********m****, and ****12 - 13%**** at sub-micron thickness in the range of ****0.75 - 0.90 ********m****.**
** ****Upon thinning the CIGS from ****2.5 to 0.75 ********m****, a loss in module efficiency of ****only 16%**** was found, stemming solely from drop of J****sc****.**
** ****High quality ****TiN films**** were produced by RE-HCS.  The TiN has considerably higher IR reflectivity than Mo.  TiN was successfully applied as a back contact for **
**    ****CIGS solar cells.  Cell efficiencies were comparable or slightly lower than those with the conventional Mo contact.  Further work should enable these **
**    ****deficiencies to be eliminated while retaining the reflection advantage. **

** ****B. Sang, L. Chen, ****M. Akhtar, R. Govindarajan, S. Guo, and ****A. E. Delahoy**
**Energy Photovoltaics, Inc.**
**Princeton, NJ 08543***** ***

*DOE Solar Energy Technologies Program Review Meeting, Denver, CO, Nov. 7-10, 2005*

** **

**1.  ****Simplified Hybrid CIGS Processing and Devices****  **

**EPV’s ****hybrid process**** for CIGS is a three-stage process conducted by linear source**
** ****evaporation of In, Ga, and Se, and sputtering of Cu [1].  The process offers:**
**    ●  ****precise control of Cu, easy scalability;**
**    ●  ****composition and bandgap control.**
**The ****simplified hybrid process ****[2]:**
** ****   ** **●**  **considerably decreases the processing time, and dramatically  increases **
**        ****the throughput of CIGS absorber;**
-     **●**  **intrinsically reduces the per-run consumption of Se.**

**3.  ****New Back Reflector Layer (TiN) by RE-HCS**

-  High quality TiN films (ρ = 53 μΩ cm) have been produced by RE-HCS.
-  Reflectivity of TiN in the long wavelength region is much larger than that of Mo.
-  TiN films have a cubic structure with a strong (111) orientation.
-  CIGS devices with TiN back contact have been fabricated that yielded
-     comparable efficiencies to those with the Mo back contact [4].

**References**
- [1] B. Sang, L. Chen, M. Akhtar,  R. Govindarajan, A. Delahoy, J. Pankow, “Cu(InGa)Se2 Thin Films by Elemental Evaporation/
-  Sputtering and Large Area Module Results,”  *Proc. 31st IEEE PVSC*, FL, pp. 215-218 (2005).
- [2] L. Chen, B. Sang, M. Akhtar, R. Govindarajan, S. Guo, J. Cambridge, A. Delahoy, M. Contreras, “ Development of Large Area,
-  High Efficiency, Thin CIGS Modules,” *Tech. Digest of 15**th** PVSEC*, Shanghai, China, pp. 85-88 (2005).
- [3] A. Delahoy, S. Guo, C. Paduraru, A. Belkind, “Reactive-environment, Hollow Cathode Sputtering: Basic Characteristics
-  and Application to Al2O3, Doped ZnO, and In2O3:Mo,” *J. Vac. Sci. Technol.* A **22**, 1697 (2004).** **
- [4] S. Guo, W. Shafarman, A. Delahoy, “TiN and TiO2:Nb Thin Film Preparation Using Hollow Cathode Sputtering with Application
-      to Solar Cells,” *AVS 52**nd** International Symposium & Exhibition*, Boston, Oct. 31, 2005.

**Reactive-environment hollow cathode sputtering (RE-HCS)**** is based on **
**metal sputtering in a hollow cathode configuration with a high flow of **
**working gas passing through the cathode [3]. **

** ****We are now able to fabricate devices with efficiencies of 12-13% **
**    ****with a CIGS absorber thickness of 0.75-0.90 ********m. **
** ****Devices over 14 % in efficiency have been fabricated with a **
**   ****CIGS absorber thickness of only 1.3 ********m.**** **
** ****Efficiency of sub-micron devices is mainly limited by a drop of J****sc****. **
**    ****The smaller absorption coefficient of CIGS at long wavelengths **
**    ****does not allow full optical absorption in a single pass. **
** ****To restore the current, a stable back contact layer with higher **
**    ****reflectivity than Mo should be developed and applied to enhance **
**    ****optical reflection at the back electrode/CIGS interface and to thus **
**    ****increase light absorption.**

**Outdoor exposure test shows that the electrical  performance of  **
** ****modules is stable.  **

- Outdoor stability test of CIGS module
- of standard thickness.

**Notes:**
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