Solar cells based on CuInGaSe 2 processed by co evaporation.

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1 Solar cells based on CuInGaSe 2 processed by co evaporation. I-Taller de Innovación Fotovoltaica y Celdas Solares 8-10/III/2011 CIE-UNAM Temixco-Morelos, México Dr. Gerardo S. Contreras Puente ESFM-IPN March 2011

2 Group of Researchers ESFM-IPN Dra. Lourdes Albor Aguilera Dr. Gerardo S. Contreras Puente Dr. Miguel Tufiño Velázquez M. en C. Jorge Sastré Hdez. CINVESTAV-IPN Dr. Arturo Morales Acevedo Dr. Gaspar Casados Cruz Dr. Máximo López López IF-BUAP Dra. Estela Calixto Rodríguez Dr. Miguel Gracía y Jiménez UNIVERSITY OF DELAWARE Dr. William N. Shafarman Dr. Shannon L. Fields UNIVERSITY OF TOLEDO Dr. Alvin D. Compaan Dr. Kristopher A. Wieland

3 OBJECTIVE Processing and characterization of CuInGaSe 2 thin films grown by thermal Co-evaporation and their evaluation as absorber layers in the substrate configuration of solar cells based on CuInGaSe 2 /CdS. X = Y = 0.9 X = (Ga) / (In + Ga) Y = (Cu) / (In + Ga)

4 SUBSTRATE CONFIGURATION SOLAR CELL STRUCTURE CuInGaSe 2 /CdS In the substrate configuration solar cells of CuInGaSe 2 with high efficiency, we use: 2 mm thick Soda-lime (SL) glass, sputtered Molybdenum as back contact, co-evaporated CuInGaSe 2 thin film (2 4 m), chemical-bathdeposited CdS thin film as windows layer ( 50 nm), sputtered ZnO as Transparent Conductive Oxide and Ni/Al grids as front contact for the current collection.

5 DEPOSITION METHOD OF CuInGaSe 2 Thermal coevaporation Among the several techniques that have been used to obtain CuInGaSe 2 (CIGS) thin films, the thermal coevaporation technique still have the best result, when these films are applied on solar cells. Standard (single-process): This is a high vacuum process (10-6 Torr) where the elements Cu, In, Ga and Se 2 are evaporated at the same time on a Sodalime/Mo substrate, with the substrate temperature between 400 to 600 ºC, in a time of min, a CIGS thin film with 4-6 m of thickness is obtained. The temperatures of the metallic sources are function of its evaporation rates and temperature around 1000 ºC.

6 EXPERIMENTAL SYSTEM SETUP

7 Mo(110) (220)/(204) (116)/(312) IntensIity (a.u.) Intensity (a.u.) B 2 /E CIGS A 1 Cu 2-X Se A 1 CIGS (112) EXPERIMENTAL DETAILS Processing of CIGS thin films The CIGS thin films processed on Mo (Toledo, Oh.) substrate showed from X-Ray diffractograms that are preferentially oriented at the (112) direction, and the (220)/(204), (116)/(312) directions of the chalcopyrite phase were also identified. CIGS6: X = 0.21 and Y = 0.61 (CuIn 0.79 Ga 0.21 Se 2 ) 1600 CIGS CIGS Angle Raman Shift (cm -1 )

8 (220)/(204) (116)/(312) Intensity (a.u.) Mo(110) Intensity (a.u.) (112) A 1 Cu 2-X Se A 1 CIGS B 2 /E CIGS EXPERIMENTAL DETAILS Processing of CIGS thin films Raman Spectroscopy of the CIGS thin films processed with Mo (Toledo) substrate indicates the frequency of the symmetric mode A 1, related to the chalcopyrite CIGS phase, at 184 cm -1, which represents the vibration of the Se anions with the cations at rest, and also exhibit a combination of the modes B 2 /E approximately at 238 cm -1 and the probable mode A 1 at 260 cm -1 related to Cu-Se compounds like Cu 2-X Se Angle 2 CIGS Raman Shift (cm -1 ) CIGS8

9 EXPERIMENTAL DETAILS We started the process to obtain CIGS thin films, by changing the growth parameters. We started with: T SUBSTRATE = 350 ºC, T Cu = 1200 ºC, T In = 925 ºC, T Ga = 1025 ºC and T Se = 210 ºC, and we obtain the composition of each of the element on these films and the critical parameters X = [Ga]/([In]+[Ga]) and Y = [Cu]/([In]+[Ga]). The table shows the experimental parameters of the 5 growing process using SL/Mo substrate supplied by University of Delaware: Sample T Sustrate (ºC) T Ga (ºC) T In (ºC) T Cu (ºC) T Se (ºC) Deposition time (min) Pressure (10-6 Torr) CIGS CIGS CIGS CIGS CIGS

10 EXPERIMENTAL DETAILS Processing of CIGS thin films CIGS 8-1: X= 0.21, Y= 0.72 (CuIn 0.79 Ga 0.21 Se 2 ) Cu = %At, In = %At, Ga = 5.78 %At, Se = %At.

11 (211) Intensity (a.u.) Mo(110) (116)/(312) A 1 CIGS Intensity (a.u.) (220)/(204) (112) EXPERIMENTAL DETAILS Processing of CIGS thin films CIGS 8-1: X= 0.21, Y= 0.72 (CuIn 0.79 Ga 0.21 Se 2 ) Cu = %At, In = %At, Ga = 5.78 %At, Se = %At. Angle 2 CIGS Raman Shift (cm -1 ) CIGS 8-1

12 EXPERIMENTAL DETAILS The table shows the elemental composition of the 5 samples (EDS) described above with the compositional rates X = [Ga]/([In]+[Ga]) y Y = [Cu]/([In]+[Ga]). Samples [Cu] %At [In] %At [Ga] %At [Se] %At CIGS CIGS CIGS CIGS CIGS X Y

13 EXPERIMENTAL DETAILS The table shows the growth parameters of the another 3 samples beyond the optimization of the critical growth parameters. Sample T Substrate (ºC) T Ga (ºC) T In (ºC) T Cu (ºC) T Se (ºC) Deposite time (min) Pressure (10-6 Torr) CIGS CIGS CIGS

14 (211) Mo(110) (220)/(204) (116)/(312) Intensity (a.u.) (112) EXPERIMENTAL DETAILS Processing of CIGS thin films CIGS 12: X= 0.21, Y= 0.73 (CuIn 0.79 Ga 0.21 Se 2 ) CIGS Cu = %At, In = %At, Ga = 5.61 %At, Se = %At Angle 2

15 (211) Mo(110) (116)/(312) Intensity (a.u.) (220)/(204) (112) EXPERIMENTAL DETAILS Processing of CIGS thin films CIGS 13: X= 0.21, Y= 0.69 (CuIn 0.79 Ga 0.21 Se 2 ) CIGS Cu = %At, In = %At, Ga = 5.54 %At, Se = %At Angle 2

16 EXPERIMENTAL DETAILS Processing of CIGS thin films The table shows the elemental composition of the 3 CIGS (EDS) thin films as described before, with their compositional rates, X = [Ga]/([In]+[Ga]) and Y = [Cu]/([In]+[Ga]): Sample [Cu] %At [In] %At [Ga] %At [Se] %At X Y CIGS CIGS CIGS

17 Compositional and SEM characterization of the CIGS thin film which was used to fabricate the photovoltaic devices (Univ. of Delaware). Film composition: Cu = %At, In = %At, Ga = 9.74 %At, Se = %At. X = 0.37 Y = 0.92 CuIn 0.63 Ga 0.37 Se 2

18 Compositional and SEM characterization of the CIGS thin film which was used to fabricate the photovoltaic devices (Univ. of Delaware). Film composition: Cu = %At, In = %At, Ga = 9.74 %At, Se = %At. X = 0.37 Y = 0.92 CuIn 0.63 Ga 0.37 Se 2

19 J (ma/cm 2 ) Current vs. Voltage characterization of the CuInGaSe 2 thin film solar cells JS17-2 Ilum = 10.5 % JS18-4Ilum = 10.9 % V (Volts)

20 Output electrical parameter of CuInGaSe 2 thin film solar cells. Sample Area (cm 2 ) R S ( -cm 2 ) V mp (mv) J mp (ma/cm 2 ) V OC (mv) J SC (ma/cm 2 ) FF (%) (%) JS JS

21 Work in progress DC-RF Sputtering

22 Thanks for your attention!!