The lead-free perovskite-based heterojunction C 2 N/CsGeI 3 : 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, C 2 N/CsGeI 3 , 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 CsGeI 3 to the C 2 N layer. Moreover, based on the work function, it is confirmed that the electrons are transferred in a Z-scheme mechanism after the CsGeI 3 contacts with the C 2 N layer. Under light irradiation, the construction of the C 2 N/CsGeI 3 heterojunction significantly enhances optical absorption within the range of visible-light wavelengths. Additionally, the impact of interfacial strain on the C 2 N/CsGeI 3 is explored and discussed. These findings not only suggest that the C 2 N/CsGeI 3 heterojunction holds promise for photovoltaic applications but also provide a theoretical insight into lead-free perovskite-based functional materials.