Arrays of CZTS sensitized ZnO/ZnS and ZnO/ZnSe core/shell nanorods for liquid junction nanowire solar cells

• Liquid junction solar cells with aligned nanorod arrays were made and tested.
• Vertically aligned ZnO NR and CZTS NP were used to obtain core/shell structure.
• ZnS or ZnSe was used as buffer layer in ZnO/Al:ZnO/buffer/CZTS configuration.
• High PCE (2.2%) is due to large interfacial area and short charge transport pathway.
• Aligned core/shell nanorod assembly gives better output than thin film solar cells.

Copper–zinc–tin–sulfide (Cu2ZnSnS4 or CZTS) is an important p-type semiconductor material for solar cell applications. A unique architecture for liquid junction solar cell made of ZnO/Al:ZnO/ZnS or ZnSe/CZTS core/shell vertically aligned nanorods array is reported. Over fluorine-doped tin oxide (FTO) coated glass, vertically aligned Al-doped zinc oxide nanorods (VANR) were grown over ZnO seed layer. It was followed by surface transformation of ZnO nanorods to ZnS or ZnSe through solubility constant (Ksp) difference induced anion exchange in a S2− or Se2− solution to produce ZnO/ZnS and ZnO/ZnSe core–shell (CS) structures. Separately, CZTS nanoparticles were synthesized from high temperature arrested precipitation and subsequently used for sensitization of ZnO/ZnS CS-VANR nanostructures. Cu2S and polysulfide were employed as counter-electrode and electrolyte respectively for fabrication of liquid junction solar cells. FE-SEM, HRTEM, X-ray diffraction and Raman spectroscopy techniques were employed for microstructural, morphological and compositional characterization of different component materials. The J–V measurements of the solar cell correspond to a several fold higher power conversion efficiency than similar device with thin film multilayer planar configuration involving same amount of materials. The aligned core/shell nanorods configuration offers an increase in the interfacial area by several folds, shorter pathway for charge transport and efficient photon absorption.

Liquid junction solar cells based on CZTS sensitized ZnO/ZnSe core/shell nanorods arrays are synthesized and yielded a power conversion efficiency of 2.2% with JSC of 10.46 mA/cm2 and VOC of 0.49 Volts.Figure optionsDownload as PowerPoint slide