Hysteresis and Transient Behaviour in Current Voltage Measurements of Antimony Selenide Solar Cells

Antimony selenide (Sb₂Se₃) is an attractive light-absorber used in low-cost, non-toxic, earth-abundant thin-film solar cells with rapidly rising efficiency values. Currently, many n-type metal oxides have been investigated as buffer layers in Sb₂Se₃ solar cell architectures. Among them, titanium oxide (TiO₂) is commonly used as the buffer layer because of its significant optoelectrical properties. The current density−voltage measurement of Sb₂Se₃solar cells in FTO/TiO₂/Sb₂Se₃/P3HT/Au configuration shows a hysteresis-like distortion that depends on the voltage scan direction, scan rate, scan range, and voltage bias conditions prior to measurement. The presence of hysteresis can significantly influence the photovoltaic properties of devices, which can overestimate or underestimate the accurate power conversion efficiency of solar cells. The fabricated solar cells showed a normal hysteresis where the forward scan result exhibits lower performance than the reverse scan under certain circumstances. We identify this phenomenon is caused due to charge carrier accumulation which may be because the capacitive charge is quickly discharged through charge separation. In addition, the accumulation of oxygen vacancies at the TiO₂/Sb₂Se₃ interface can reduce charge extraction, and at the same time, significantly accelerate the charge recombination at the interface, which also leads to unfavorable hysteresis. However, the hysteretic effects are not observed in devices utilizing alternative buffer layers like ZnO and SnO₂, suggesting that the buffer absorber interfaces have a significant effect on transients in Sb₂Se₃ absorber devices. Therefore, further improvements of Sb₂Se₃solar cells are essential through careful surface engineering of existing TiO₂ or through a judicious choice of alternative interfacial layers.