Fundamental Physical Characterization of Sb₂Se₃-Based Quasi-Homojunction Thin Film Solar Cells

A new type of solar cell based on Cu-doped (p-type) and I-doped (n-type) Sb₂Se₃ has been designed and fabricated using magnetron sputtering with two different thicknesses of absorber. The overall objective is for better understanding the charge recombination mechanism, especially at the interface region. The investigation has been specifically performed using IMPS (intensity modulated photocurrent spectroscopy), IMVS (intensity modulated photovoltage spectroscopy), and diode characterizations. It has been found that an increase of the absorber thickness leads to a shorter carrier lifetime, but longer diffusion length and lower trap density, resulting in significantly better performance. Furthermore, it is demonstrated that trap-assisted recombination does not affect the short-circuit current density (J_sc), but significantly decreases the open-circuit voltage (V_oc). As a result, an encouraging power conversion efficiency (PCE) of 2.41%, fill factor (FF) of 41%, J_sc of 20 mA/cm², and V_oc of 294 mV are obtained. Most importantly, key parameters for further increasing the PCE have been identified.