nz0c00110_si_001.pdf (239.56 kB)
Polymeric Electron-Selective Contact for Crystalline Silicon Solar Cells with an Efficiency Exceeding 19%
journal contribution
posted on 2020-02-24, 19:13 authored by Wenbo Ji, Thomas Allen, Xinbo Yang, Guosong Zeng, Stefaan De Wolf, Ali JaveyCarrier-selective
contacts have become a prominent path forward
toward efficient crystalline silicon (c-Si) photovoltaics. Among the
proposed contacting materials, organic materials may offer simplified
and low-cost processing compared with typical vacuum deposition techniques.
Here, branched polyethylenimine (b-PEI) is presented as an electron-transport
layer (ETL) for c-Si solar cells. The incorporation of a b-PEI interlayer
between c-Si(n) and Al leads to a low contact resistivity
of 24 mΩ cm2. A silicon heterojunction solar cell
integrated with b-PEI is demonstrated achieving a power conversion
efficiency of 19.4%, which improves the benchmark efficiency of a
c-Si solar cell with an organic ETL. This electron selectivity of
b-PEI is attributed to its Lewis basicity, i.e., electron-donating
ability, promoting favorable band bending at the c-Si surface for
electron transport. Moreover, several other Lewis base polymers perform
as efficient ETLs in organic/c-Si hybrid devices, indicating Lewis
basicity could be a guideline for future organic ETL design.