Unveiling the role of ethylene glycol for enhanced performance of PEDOT:PSS/Silicon hybrid solar cells

Recently, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and n-silicon (n-Si) based hybrid solar cells (HSCs) are given significant attentions owing to their cost-effective processing and promising photovoltaic performances. Pristine PEDOT:PSS, however, due to its limited electrical conductivity, cannot yield highly efficient HSCs. Doping of ethylene glycol (EG) in PEDOT:PSS boosts its electrical properties. However, role of EG on the formation, working mechanism of PEDOT:PSS/n-Si heterojunction and the performance of the HSCs are rarely explained. Herein, influence of EG on the optical, structural, electrical, and passivation properties of PEDOT:PSS along with polymer/n-Si heterojunction formation is investigated. HSCs with significantly enhanced power conversion efficiency (by ∼3.5 fold) is achieved for an optimal EG concentration (as compared to pristine PEDOT:PSS) on micro-engineered thin n-Si wafers even in the simplest device design. Optimal EG induces a strong inversion layer (p+-n junction) in n-Si at the polymer/Si interface enabling efficient separation and transportation of photo-carriers and hence enhanced solar cell performances. Formation of EG dependent strong electric field at polymer/n-Si interface is confirmed by the results of minority carrier lifetime, J-V characteristics, quantum efficiency, electrochemical impedance and C-V measurements of the HSCs. Role of EG in making an efficient PEDOT:PSS/n-Si solar cell is explained which may pave the way for further advancement of the cost-effective hybrid solar cell technology.