Dr. Meicheng Li
Professor, School of Renewable Energy, North China Electric Power University, China.

Speech title: Surface Passivation of Interfacial Modification of the Novel Solar Cells

Abstract: The carrier lifetime and the doping property of the photoabsortion materials are essential factors determining their application in solar cells. Surface modification is a practical approach to get unique contact of two different materials and realize special interfacial structure and status between two buildingblock layers. Here, we talked about the surface passivation of silicon nanostructure using for hybrid solar cells, and even the carrier lifetime and the doping property of the lead halide perovskites in solar cells.
First, a promising passivation scheme in ultrathin silicon-PEDOT:PSS hybrid solar cells is presented. In this scheme, an i a-Si layer is inserted between the c-Si and the PEDOT:PSS, and an i a-Si/n+ a-Si bilayer is inserted between the back surface of the c-Si and the back electrode. As we know, amorphous Silicon Layer can passive the c-Si surface excellently in traditional hetero-junction silicon cells with intrinsic layer (HIT). Here, we try to transplant such an Amorphous Silicon Layer to the Si/PEDOT:PSS interfaces. Using this strategy, despite the mismatch of bandgaps between the amorphous silicon and the PEDOT:PSS，carriers can be transported through the amorphous silicon layer for tunneling effect, by limiting its thickness to be about ~10 nm. We demonstrate that this passivation scheme employing amorphous silicon layers at both interfaces should be a promising method in the ultrathin silicon/polymer hybrid solar cells.
And then, interfacial modification is a practical approach to reduce carrier recombination at the interface of the perovskite films and other layers(HTM or ETL) caused by the trap states and the intrinsic nature of polycrystalline organometallic perovskites. Herein, an F4TCNQ interfacial layer is introduced, which possess dual function, i.e., surface passivation and interfacial doping of the perovskite. The perovskite solar cells (PSCs) with the dual function interfacial layer exhibit remarkable improvement in device performance and show enhanced long-term stability in ambient air without device encapsulation. We present a novel TiO2 embedded structure for highly-efficient and stable PSCs. The performance of the PSCs is significantly improved with the efficiency increasing from 16.6% for planar structure to 19.2% for the embedded structure. Furthermore, the TiO2 embedded PSCs, show excellent stability with efficiency keeping approach 80% (for average) or 90% (for the best) after being exposed in air for 28 days without encapsulation.