Formation of van der Waals Stacked p–n Homojunction Optoelectronic Device of Multilayered ReSe₂ by Cr Doping

Abstract The formation of p‐ or n‐type material via impurity doping should be crucial and essentially prior to the establishment of junction devices in semiconductor processing. Especially in a 2D transition‐metal dichalcogenide (TMD), dopant selection for growing p‐ and n‐type TMD semiconductors may suffer much higher difficulty and complexity than conventional Si and III–V compounds owing to the complicated valences occurred in transition metals. Different amount of chromium doped in ReSe₂ interestingly showing dissimilar carrier types of p‐ReSe₂ with Cr 10% and 20% doping and n‐ReSe₂ with Cr 0%, 1%, and 5% doping, respectively, is presented here. According to structural and optical characterization, the crystal structure and bandgap of the Cr‐doped ReSe₂ remain unchanged in which a deeper donor of Cr⁶⁺ can exist in n‐ReSe₂ (1% and 5%) while a shallow acceptor of Cr³⁺ may appear in p‐ReSe₂ multilayer (10% and 20%). A p–n homojunction light‐emitting diode made by stacking multilayered n‐ReSe₂ (Cr 0%) and p‐ReSe₂ (Cr 20%) is first fabricated, and it emits an electroluminescence of ≈946 nm from the band edge. Another p–n homojunction solar cell is also manufactured to exhibit a maximum axial conversion efficiency of η ≈ 1.05% along with the b‐axis polarization of ReSe₂.