Photoconversion efficiency in atomically thin TMDC-based heterostructures.

Nowadays, two-dimensional materials such as graphene, phosphorene, and transition metal dichalcogenides (TMDCs) are widely employed in designing photovoltaic devices. Despite their atomically thin (AT) thicknesses, the high absorption of the TMDCs makes them a unique choice in designing solar absorptive heterostructures. In our exploration of finding the most efficient TMDC contacts for generating higher photocurrents, we carefully examined the physics behind the external and internal quantum efficiencies (EQEs and IQEs) of different AT heterostructures at the solar spectrum. By minute examination of the EQEs of the selected TMDC-based heterostructures, we show that the absorption of each consisting TMDC and the gradient of the electronic structure of them at their contact, determine mostly the photocurrent generation efficiency of the solar cells. The promising EQE (IQE) value of 0.5% (1.4%) is achieved in WSe/MoSe contact at the wavelength of 433 nm. In the case of the multilayers of TMDCs, together with the light absorption increase of the multilayers the EQE of the heterostructures generally increases, while the competitive nature of the electronic structure gradient and the absorption makes this increase nonmonotonic. The TMDC-based heterostructures which are investigated in this work, pave a new way in designing miniaturized and efficient optoelectronic devices.