Deposition and characterization of earth abundant CuZnS ternary thin films by vacuum spray pyrolysis and fabrication of p-CZS/n-AZO heterojunction solar cells

We report fabrication of solar cell device with Copper Zinc Sulfide (CZS) thin films as absorber layer. CZS thin films prepared using chemical spray pyrolysis technique at a pressure of 10⁻³ mbar at different substrate temperatures. Structural, morphological, optical, compositional and electrical properties of as prepared films are investigated. Structural analysis shows crystalline nature with mixed phase containing CuS-ZnS binary composite. Atomic Force Microscopy analysis shows the average particle size of 88 nm. Value of work function obtained from ultraviolet photoelectron spectroscopy is 4.58 eV. The band gap of the as-prepared films varies from 1.62 to 2.06 eV. Hall effect measurement proves the p-type nature for all the deposited films. Samples deposited at 350°C shows carrier concentration of 10²¹ cm⁻³ and electrical conductivity of 526 S cm⁻¹. Solar cell device structure of has been fabricated using the CZS sample deposited at 350°C. The cell parameters obtained are V_oc = 0.505 V, I_sc = 4.97 mA/cm², FF = 64.28% and η = 1.6 ± 0.05%.