Combined CBD-CVD Technique for Preparation of II-VI Semiconductor Films for Solar Cells

II-VI and IV-VI semiconductor films for solar cell applications, namely, CdTe, CdSe, PbSe and PbTe, can be prepared in two-stage deposition process. In this work we illustrate the two-stage process to obtain PbTe films from precursor plumbonacrite films deposited by chemical bath deposition (CBD). In the first stage, plumbonacrite Pb10(CO3)6O(OH)6) films were deposited onto glass substrate by (CBD), using ammonia-free low-temperature process in alkaline aqueous solution with corresponding ion sources. Then, in the second stage, the obtained film was placed in a Chemical Vapor Deposition (CVD) Hot Wall reactor with gas transportation, where it acted as substrate in a reaction of substitution of non-metallic film component by Te, thus forming PbTe films. The nitrogen flux of 0.25 lt/min was used as transporting gas. The source temperature was adjusted between boiling (Tb) point and melting point (Tm) with the aim to control the flux gas of the source(Tellurium source, Tm=449.51 °C,Tb=988 °C). The substrate temperature was adjusted to improve the quality of the film. Besides, a two-stage CBD process was also studied, where first a higher band gap semiconductor layer was deposited (CdS) and then a smaller gap material (PbS) was deposited above it. The structural and optical investigation of the films obtained proved their high quality that determines the possibility of utilization them as elements of solar cells, in particular, multi-junction cells. As an example, solar cell of CdS/PbS type was constructed showing quantum efficiency above 25%. The technique as a whole is versatile and relatively cheap, it could be used for preparation of a large variety of semiconductor materials.