1. Zn(O,S):Al transparent conductive film for buffer-free Cu(In,Ga)Se 2 solar cells 1-1-1 Nojihigashi Kusatsu Shiga 525-8577, Japan phone/fax: 077-561-4836, e-mail: ro0009iv@ed.ritsumei.ac.jp Conclusions 2013/12/14 日 Mid-term M1 Presentation Site: Ritsumeikan University Experiment ZnO 1-x S x :Al films properties (Transmittance, Resistivity) ・ Transmittance of ZnO 1-x S x :Al films (0.00 ≦ S/(S+O) ≦ 0.15) ) ・ ZnO 1-x S x :Al films Hall Effect Solar cell characteristics Introduction Yuta Mizumoto, Jakapan Chantana, Takashi Minemoto C-1 Currently, a CdS thin film or ZnO 1-x S x thin film are utilized as a buffer layer in high efficiency CIGS solar cell TCO/CIGS causes severe shunting carrier recombination at TCO/CIGS interface, due to negative CBO (around -0.2 eV). 1) Dry process 2) Eliminating chemical bath deposition process 3) Structure simplification Ideally, only electrode, p-type semiconductor and n-type semiconductor are sufficient for function of solar cells Merit of buffer-free Demerit ・ ZnO 1-x S x :Al films properties (Transmittance and Resisitivity) Conduction band offset (CBO) control by changing the S content [1] We investigated the characteristics of CIGS solar cells with the AZO 1-x S x TCO ・ characteristics of CIGS solar cells with the AZO 1-x S x TCO ZnO 1-x S x :Al filmsCBO(Control ΔE C ) CIGS 1.1eV AZOS ZnO 1-x S x :Al films deposition method : Co-sputtering of AZO and ZnS targets Applied power of each target range AZO 110~160 W, ZnS 0~25 W S/(S+O) oxygen-sulfur ratios from 0.00 to 0.15 Eg is calculated from transmittance The current density-voltage (J-V) characteristics The external quantum efficiency (EQE) characteristics Measure The structure of buffer-free solar cell S/(S+O)Eg(eV) Average T (%) 400-1100(nm) 0.003.3291.1 0.103.1289.1 0.153.0088.8 Eg is calculated from transmittance: With S content increased, Eg is getting smaller. S/(S+O) Sheet Resistance [Ω/□] Resistivity [Ω∙cm] Hall mobility [cm²/V∙s]Career density(cm -3 ) 0.00521.65×10 -3 8.264.56×10 20 0.101383.93×10 -3 2.925.44×10 20 0.152607.09×10 -3 2.992.94×10 20 ・ High transmittance of nearly 89% at range from 400nm-1100nm ・ Sheet resistance increased with S/(S+O) ･ Al-doping efficiency decreased with increased S. ・ High EQE of buffer-free solar cell (short wavelength) Absence of buffer layer increases absorption ・ Low V OC of buffer-free solar cell Recombination at ZnO 1-x S x :Al/CIGS interface ※ Reference cell structure Al/NiCr/ZnO 1-x S x :Al/CdS/CIGS/Mo/SLG EQE ※ Measured cell area:0.12cm 2 J-V S/(S+O) J SC (mA/cm 2 ) V OC (V)FF(%)Eff(%) Relative value of Eff with CdS(%)%) R S (  ･ cm 2 ) R Sh (  ･ cm 2 ) 0.00 CdS30.00.65676.615.10.182394 without- CdS 30.50.58164.711.576760.24736 0.10 CdS31.60.61768.013.30.40950 without- CdS 28.90.56368.111.183830.45816 0.15 CdS29.70.61365.411.90.23565 without- CdS 32.00.53661.210.580.38386 ・ With increased S contents, decrease Eff (0.00 ≦ S/(S+O) ≦ 0.15) ・ Absence of buffer layer increases absorption at short wavelength. ・ The buffer-free CIGS cell with Zn(O,S):Al film show highest relative value of cell efficiency is 88% (10.5%) at S/(S+O)=0.15, probably due to lower interface recombination. ・ With S content increased, Eg is getting smaller. ・ High transmittance of nearly 89% at range from 400-1100nm ・ Sheet resistance and Resistivity increased with S/(S+O) [1] Takashi. Minemoto, Jasmeen Julayhi, "Buffer-less Cu(In,Ga)Se2 solar cells by band offset control using novel transparent electrode ", Current Applied Physics 13 (2013) 103-106 Shift Solar cell parameter CBO control using TCO is required to prevent severe shunting ･ These results indicate that the buffer-free cell concept is achievable, and the Zn(O,S):Al is acceptable as a TCO for buffer-free CIGS solar cell; but further improvement is needed. ZnO:Al films Buffer-free solar cell with ZnO:Al films