The lead-free perovskite-based heterojunction C₂N/CsGeI₃: an exploration for superior visible-light absorption

Halide perovskites have distinguished themselves among the numerous optoelectronic materials due to their versatile processing technology and exceptional optical response. Unfortunately, their stability and toxicity from heavy metals severely hamper their development, in addition to the challenge of further improving photovoltaic performance. Hence, a lead-free perovskite-based heterojunction, C₂N/CsGeI₃, is investigated using a hybrid density functional, including electron structures, charge density differences, optical properties and more. The study reveals the presence of a built-in electric field directed from the CsGeI₃ to the C₂N layer. Moreover, based on the work function, it is confirmed that the electrons are transferred in a Z-scheme mechanism after the CsGeI₃ contacts with the C₂N layer. Under light irradiation, the construction of the C₂N/CsGeI₃ heterojunction significantly enhances optical absorption within the range of visible-light wavelengths. Additionally, the impact of interfacial strain on the C₂N/CsGeI₃ is explored and discussed. These findings not only suggest that the C₂N/CsGeI₃ heterojunction holds promise for photovoltaic applications but also provide a theoretical insight into lead-free perovskite-based functional materials.