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Vacuum free, solution based routes to the preparation of chalcopyrite absorbers for solar cells promise options in device design and manufacturing that are not provided by the standard vacuum based approaches. In order to fully exploit these options, the precursor should contain neither nanoparticles nor hazardous chemicals, and it should be stable under ambient conditions. In this contribution we report on CuIn(S,Se)2 thin film preparation based on spin coating of an air stable molecular ink containing metal chlorides and thiourea in organic solvents. Several key parameters directly influencing the performance of the resulting solar cells have been identified. Wetting of the glass/Mo substrate has been adjusted by varying the concentration of ethylene glycol butyl ether in the ink. Before annealing in Ar/Se at atmospheric pressure, several cycles of ink deposition and drying can be used to increase the thickness of the precursor stack. Careful balancing of ink concentration, number of precursor deposition cycles, and annealing temperature profile will transform the multi-layer precursor into a sufficiently thick, continuous, large grained film as required for high quantum efficiency, and good red response of the cells. These optimizations aimed at high photo current have already led to an efficiency of 9.5%. [ABSTRACT FROM AUTHOR]

High quality polycrystalline bilayers of aluminium doped ZnO (Al:ZnO) were successively electrodeposited in the form of columnar structures preferentially oriented along the (1011) crystallographic direction from aqueous solution of zinc nitrate (Zn(NO3)2) at negative electrochemical potential of EC = (-0.8)-(-1.2) V and moderate temperature of 80 °C on gallium rich (30% Ga) chalcopyrite selenide Cu(In,Ga)Se2 (CIGS) with chemically deposited ZnSe buffer (ZnSe/Cu(In,Ga)Se2/Mo/glass). The aluminium doped ZnO layer properties have initially been probed by deposition of Al:ZnO/i-ZnO bilayers directly on Mo/glass substrates. The band-gap energy of the Al:ZnO/i-ZnO reference layers was found to vary from 3.2 to 3.7 eV by varying the AlCl3 solute dopant concentration from 1 to 20 mM. The electrical resistivity of indium-pellet contacted highly doped Al:ZnO sheet of In/Al:ZnO/i-ZnO/Mo/glass reference samples was of the order ρ ~10-5 Ω·cm; the respective carrier concentration of the order 1022 cm-3 is commensurate with that of sputtered Al:ZnO layers. For crystal quality optimization of the bilayers by maintenance of the volatile selenium content of the chalcopyrite, they were subjected to 2-step annealing under successive temperature raise and N2 flux regulation. The hydrostatic compressive strain due to Al3+ incorporation in the ZnO lattice of bilayers processed successively with 5 and 12 mM AlCl3 dopant was "h = -0.046 and the respective stress εh = -20 GPa. The surface reflectivity of maximum 5% over the scanned region of 180-900 nm and the (optical) band gap of Eg = 3.67 eV were indicative of the high optical quality of the electrochemically deposited (ECD) Al:ZnO bilayers. [ABSTRACT FROM AUTHOR]