Effects of ammonia concentration on the formation of CdS fabricated via microwave‐assisted chemical bath deposition

Abstract

The microwave-assisted chemical bath deposition (MACBD) process was successfully developed in this study for the preparation of cadmium sulfide (CdS) films as the buffer layers in Cu(In,Ga)Se 2 solar cells. The MACBD process reduces the reaction time to just 8 min. During the MACBD process, increasing the concentration of NH 4 OH in the solution effectively reduced the thickness of the films as well as the particle sizes of in CdS films. At high NH 4 OH concentrations, the heterogeneous nucleation of CdS dominated, and the formation of films was controlled via the ion-by-ion growth mechanism. Increasing the concentration of NH 4 OH from 1 to 2.5 M significantly increased the conversion efficiency of the fabricated CIGS solar cells from 7.15% to 9.12%. The increase in the efficiency was attributed to an increase in the absorption of incident light and the enhancement of the carrier collection due to a reduction in the thickness of the prepared CdS films. According to diode analysis, the improvement in the diode ideality factor and leakage current was owing to the uniform coverage of CdS films and a reduction in series resistance associated with a decrease in the thickness of CdS films. When the concentration of ammonia was further increased to 3 M, incomplete coverage of CdS films on CIGS layers resulted in the formation of shunt paths and degraded the cell performance. This study demonstrated that CdS films prepared using the MACBD process with the optimum concentration of ammonia effectively improved the photovoltaic performance of Cu(In,Ga)Se 2 solar cells. K E Y W O R D S ammonia concentration, CdS buffer, CIGS solar cell, diode analysis, microwave-assisted chemical bath deposition

Large metastability in Cu (In,Ga)Se2 devices: The importance of buffer properties

“…This spread is not fully understood. Growth rates and properties of bath‐deposited buffers are sensitive to substrate, fluid velocity and flow, exact stoichiometry of precursor compounds, chemical concentrations, temperature, substrate orientation, and light . These quantities are controlled to the extent that is convenient with typical wet chemistry procedures.…”

Microstructures and photovoltaic performances of bismuth‐ion doped Cu(In,Ga)Se2 films prepared via sputtering process

“…The thin‐film solar cells based on chalcogenide compounds have extensively been investigated due to the advantages of high optical absorption coefficients, low material consumption of materials, and long‐term stability . Cu(In,Ga)Se 2 (CIGS) materials are regarded as the suitable chalcopyrite absorbers for the applications in various thin‐film based solar cells.…”