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Abstract Appropriate selection of electron buffer layer and understanding its impact on the photo‐generated charge transfer dynamics at the interfaces are critical to enhance the efficiency of solar cells. By optimizing a multilayer electron buffer composed of CdS thin film deposited on TiO 2 compact layer, we obtained a power conversion efficiency (PCE) of 5.47% for a planar solar cell of Sb 2 (S x Se 1‐ x ) 3 absorber. The PCE was significantly enhanced in the photovoltaic parameters of planar solar cells fabricated with single‐layer configuration: for example, PCE of 3.99% and 0.79% were obtained when either CdS or TiO 2 , respectively, were used. Surface photovoltage spectroscopy, transient photovoltage, and electrochemical impedance spectroscopy analyses indicated that the PCE improvement can be ascribed to a combination of 2 factors: (i) better separation and transfer of the photo‐excited free charge, provided by the beneficial energy level alignment between TiO 2 and CdS layers, and (ii) sulfur passivation upon incorporation of CdS in a multilayer configuration causing a reduction in the trap states at the interface with Sb 2 (S x Se 1‐ x ) 3 .
Jaramillo‐Quintero et al. (Fri,) studied this question.