Solution‐Processed Electron‐Selective Contacts Enabling 21.8% Efficiency Crystalline Silicon Solar Cells

Abstract

Crystalline silicon (c‐Si) solar cells with carrier‐selective passivating contacts have been prosperously developed over the past few years, showing fundamental advantages, e.g., simpler configurations and higher potential efficiencies, compared with conventional c‐Si solar cells using highly doped emitters. Herein, solution‐processed cesium halides (CsX, X represents F, Cl, Br, I) are investigated as electron‐selective contacts for c‐Si solar cells, enabling lowest contact resistivity down to about 1 mΩ cm2 for slightly doped n‐type c‐Si/CsF/Al contact. After inserting a thin intrinsic amorphous silicon (a‐Si:H(i)) passivating layer, the contact resistivity can still be kept in a low value, about 10 mΩ cm2. With full area rear‐side a‐Si:H(i)/CsF/Al electron‐selective passivating contacts, record power conversion efficiencies of about 21.8% are finally demonstrated for n‐type c‐Si solar cells, showing a simple approach to realize high‐efficiency c‐Si solar cells.

One‐Step Formation of Low Work‐Function, Transparent and Conductive MgFxOy Electron Extraction for Silicon Solar Cells

“…to form rear side metal electrode. [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ] However, this opaque stack is unsuitable for bifacial structure.…”

High‐Performance Europium Fluoride Electron‐Selective Contacts for Efficient Crystalline Silicon Solar Cells

“…Significant progress has been made in the development of dopant‐free electron‐selective contacts applied to n‐type c‐Si solar cells. Materials such as alkali/alkaline earth metal salts (e.g., LiF x , [ 8,12 ] CsF, [ 13 ] MgF 2 [ 14 ] ), transition metal oxides (TMOs, e.g., TiO 2 [ 15 ] and TaO x [ 16 ] ), alkaline earth metals (e.g., Mg, [ 17 ] Ca [ 18 ] ), alkaline earth metal oxides (e.g., MgO [ 9 ] ), transition metal nitride and oxynitride (e.g., TaN x , [ 11 ] TiN x , [ 19 ] and TiO x N y [ 20 ] ) have been reported to enhance the Ohmic contact of Al to n‐type c‐Si significantly, enabling the achievement of high‐efficiency solar cells with most of them reaching about 20%.…”

Dopant‐Free Bifacial Silicon Solar Cells

“…This is due to the need for a thick‐enough Al layer to provide the electron selectivity of dopant‐free electron‐transporting stacks. [ 9,12,13,20–26 ] A notable exception is the recently reported device using a single TiN layer as an electron‐selective contact, yet this material is opaque due to high free‐carrier density. [ 27 ]…”

“…[ 12,30 ] In that case, the contact resistance is potentially low to form a partial‐area heterocontact for dopant‐free bifacial silicon solar cells with a metal contact fraction between 10% and 50%. [ 31 ] In contrast to most electron transporting layers (0.5–10 nm), [ 6,9,13,20–24,27,32–34 ] a thick ZnO (60–140 nm) electron‐selective layer can additionally serve as a transparent antireflective coating (ARC), thus simplifying the fabrication process.…”