Nanoengineering of the Cu₂ZnSnS₄-TiO₂ interface: Via atomic layer deposition of Al₂O₃ for high sensitivity photodetectors and solid state solar cells

In this work, it is demonstrated that by applying a nanoscale Al₂O₃ film via atomic layer deposition (ALD) to the Cu₂ZnSnS₄-TiO₂ p/n junction, the adverse Sn doping effect is prevented and band alignment is optimized. EDS f-ratio mapping and XANES are used to confirm the purity and nanoscale homogeneity of CZTS. Thanks to the engineered interface by ALD Al₂O₃, high sensitivity photodetectors are designed exhibiting a novel voltage alterable spectral photoresponse. By further integrating a CdS interfacial layer, a TiO₂-Al₂O₃-CZTS/Spiro-OMeTAD/Au solid state nanostructured solar cell is eventually fabricated with an enhanced energy conversion efficiency of 4.2%.