Solution-processed ZnO as the efficient passivation and electron selective layer of silicon solar cells

Solution-processed intrinsic ZnO and Al-doped ZnO (ZnO:Al) were spin coated on textured n-type c-Si wafer to replace the phosphorus-doped amorphous silicon as the electron selective transport layer (ESTL) of the Si heterojunction (SHJ) solar cells. Besides the function of electron selective transportation, the nondoped ZnO was found to possess certain passivation effect on c-Si wafer. The SHJ solar cells with different combinations of passivation layer (intrinsic a-Si:H, SiO_x, and nondoped ZnO) and electron transport layer (nondoped ZnO and ZnO:Al) were fabricated and compared. An efficiency up to 18.46% was achieved on a SHJ solar cell with an a-Si:H/ZnO:Al double layer back structure. And, all the solution-processed nondoped ZnO/ZnO:Al combination layers present fairly good electron selective transportation property for SHJ solar cell, resulting in an efficiency of 17.13%. The carrier transport based on energy band diagrams of the rear side of the solar cells has been discussed related to the performance of the SHJ solar cells.