Cd1−xS:B/CuInSe2 interface of thin film solar cells improved with iodine passivation

Publication date: Available online 2 March 2017
Source:Thin Solid Films
Author(s): Yu-Song Cheng, Na-Fu Wang, Yu-Zen Tsai, Hsueh-Ping Liu, Chen-Ting Leng, Mau-Phon Houng
This study revealed the band gap, visible transmittance, and crystallinity variation Cd1−x S:B emitter layer at different boron concentrations, as well as the CuInSe2 absorption layer nucleation mechanism at pH values ranging from 1.53 to 2.13. CuInSe2 deposited at a pH of 1.73 showed the highest grain size (24.29nm) and approached the stoichiometric state of [Cu]/[In]=0.98, which produced was used for solar cells and Schottky diode. The conversion efficiency of Al/AZO/Cd1−xS:B/CuInSe2/Mo/Glass structure cell was 2.37% (Voc: 293mV, Jsc: 26.85mA/cm², and FF: 0.301). Moreover, the aluminum material were deposited on CuInSe2 as a Schottky diode (Al/CuInSe2/Mo/Glass), which diode was used to estimate the work function (Φ) and ideality factor (n) through Schottky barrier. These device parameters of Al/CuInSe2 structure was ΦCuInSe2 =4.791eV and n=3.52, respectively. This result revealed that the Cd1−xS:B/CuInSe2 interface state can cause Fermi-level pinning with an interface recombination velocity of 2.328×10³ cms⁻¹. This indicates the poor performance of Schottky diodes and thin film solar cells comprising Cd1−xS:B/CuInSe2. However, experimental results demonstrated that the passivation of the surface by using iodine treatment can improve the Fermi-level pinning effect on Cd1−xS:B/CuInSe2 interfaces.