Twenty Percent Efficiency Crystalline Silicon Solar Cells with Solution-Processed Electron-Selective Contacts
Zilei Wang, Jian He, Wenjie Wang, Hao Lin, Zhiyuan Xu, Qiming Liu, Shanglong Peng, Juan Hou, Deyan He, Pingqi Gao
Abstract
Carrier-selective contacts, especially in electron-selective contact (ESC), between the metal electrodes and the crystalline silicon (c-Si) substrates play a pivotal section in promoting the power conversion efficiencies (PCEs) of c-Si heterojunction solar cells. The development of ESC that can assure excellent surface passivation and low contact resistivity to the c-Si substrates while presenting a low-cost approach is crucial for practical implementation. Here, a class of solution-processed alkali metal acetates (AMAcs, AM represents lithium (Li), sodium (Na), and potassium (K)) are investigated as effective electron-selective contacts via a simple spin-coating method, which enables obvious reduction of contact resistivity (ρc) for c-Si/AMAc/Al contacts. The lowest ρc of 9 mΩ·cm2 is demonstrated for the c-Si/LiAc/Al contact. In addition, by inserting a 6 nm intrinsic amorphous silicon (a-Si:H), optimized a-Si:H(i)/LiAc ESC simultaneously provides high-quality surface passivation and contact property, with a saturated current–density J0c of 12 fA/cm2 and a ρc of 11 mΩ·cm2. PCEs of 19.8 ± 0.3% have been realized for the devices with a full-area rear a-Si:H(i)/LiAc/Al contact, displaying the enormous potential of this electron-selective contact for low-cost and high-efficiency c-Si solar cells.