Mater. Res. Soc. Symp. Proc. Vol. 1447 © 2012 Materials Research Society DOI: 10.1557/opl.2012. Development of sprayed CuInS 2 thin film absorber for nanostructured solar cell Atanas Katerski 1 , Erki Kärber 1 , Malle Krunks 1 , Valdek Mikli, Arvo Mere 1 1 Tallinn University of Technology, Ehitajate tee 5, Tallinn, 19086, Estonia ABSTRACT CuInS 2 (CIS) films were prepared by chemical spray pyrolysis (CSP) method in air using CuCl 2 , InCl 3 and SC(NH 2 ) 2 as precursor materials. The effect of the absorber growth temperature in the interval of 240-350 °C and precursors’ molar ratio in the spray solution on the CIS film properties and ZnO/In 2 S 3 /CIS-type CSP-deposited thin film solar cell output characteristics has been studied. CIS films were characterized by XRD and EDX, solar cells were characterized by IV curves in dark and under illumination, and junction barrier height (Φ b ). The highest Φ b of 1170 meV and open circuit voltage (V oc ) of 560 mV were recorded for the cell with CIS absorber grown at 250 °C. Increasing the CIS deposition temperature decreases Φ b and V oc , makes a component of solar cell photosensitive and increases current density. The precursors’ molar ratio in spray solution becomes relevant at CIS growth temperatures higher than 300 °C as deposition of thiourea-rich solutions suppresses oxide formation in CIS layer and contributes to higher open circuit voltage. INTRODUCTION Nanostructured solar cells are in the focus of interest last several years due to extended performance at low cost. The concept was described firstly for dye-sensitised solar cells [1]. Later a dye was replaced with an extremely thin inorganic absorber (ETA) and these type cells are called ETA-cell [2]. ETA concept allows reducing requirements for absorber layer electronic properties and opens the possibility for preparation of nanostructured solar cells by chemical low cost deposition methods. There are some modifications of ETA solar cells. So-called 3D solar cell, where the meso-porous TiO 2 electrode is sensitized with CuInS 2 absorber and the same material is used as p-conductor, presents light to electricity conversion efficiency of 7 % [3]. ETA cells with highest efficiency of 5.1% on mesoporous TiO 2 have been realized using Sb 2 S 3 as absorbing material in TiO 2 /Sb 2 S 3 /CuSCN type cell [4]. If ZnO nanostructured layer comprising ZnO nanorods is used instead of TiO 2 mesoporous layer, the efficiency of 3.4 % is reported for the cell using In 2 S 3 as an absorber and CuSCN as p-conductor [5]. Recently our group presented the method for preparation of nanostructured solar cell based on ZnO nanorod layer and CuInS 2 (CIS) as an absorber applying chemical spray pyrolysis (CSP) method for preparation of all component layers in solar cell structure ZnO/In 2 S 3 /CuInS 2 [6]. The efficiency of 4.17 % has been obtained with this type cell with no optimization of layer thicknesses or absorber growth conditions [7]. This study has aim to investigate sulfur source (thiourea) amount in CIS precursor solution and film growth temperature on the structure and elemental composition of sprayed CIS films and thin film solar cell output characteristics. CIS films were characterized by XRD and EDX techniques. Solar cells based on sprayed CIS absorber were characterized by IV curves in dark and under illumination and temperature dependence of open circuit voltage (V oc ) to determine the junction barrier height (Φ b ). 1511