Ternary alloyed BaxCd1−xS nanocrystals: Synthesis, bandgap tuning, and photovoltaic performance

Abstract

This work reports the synthesis and photovoltaic properties of a new semiconductor–ternary alloyed BaxCd1−xS nanocrystals, prepared by replacing a fraction of the Cd2+ ions in the host CdS with Ba2+ ions (x = 0−0.13) using the sequential ionic layer adsorption and reaction. Optical measurements revealed a decreasing bandgap in BaxCd1−xS from 2.24 to 2.14 eV with increasing x, increasing the optical absorption range from 300 to 553 nm in CdS to 300−579 nm in BaxCd1−xS. Liquid-junction semiconductor quantum dot-sensitized solar cells (QDSSCs) were fabricated from BaxCd1−xS nanocrystals using polysulfide electrolyte and CuS counter electrode. The Ba0.09Cd0.91S QDSSC (x = 0.09) yielded the best power conversion efficiency (PCE) of 3.95% under 1 sun, which is 33% higher than that (2.96%) of the host CdS. A ZnS passivation layer treatment on the best Ba0.09Cd0.91S sample increased the PCE to 4.57% (JSC = 9.33 mA/cm2, Voc = 0.80 V, fill factor = 61.2%) under one sun. The PCE further increased to 5.21% under a reduced light intensity of 0.1 sun. This work demonstrates the potential of tunable optoelectronic properties in BaxCd1−xS by controlling the Ba content and enhancing the photovoltaic performance by increasing the absorption range.