Mechanism for Improving Kesterite Solar Cells Performance via Filed Passivation Effect Induced by V‐Doped MoSe₂Interface Layer at Back Interface

Abstract

One of the key issues impeding the enhancement of power conversion efficiency (PCE) of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells is the severe carrier recombination at CZTSSe/MoSe2 back interface, primarily arising from the reverse electric field formed between CZTSSe and n‐type MoSe2 produced after selenization. To inhibit recombination at back interface, herein, the MoSe2 layer is converted from n‐type to p‐type by V doping in site through reaction of V‐alloyed Mo (Mo:V) back electrode with Se during selenization, and CZTSSe solar cells with p+‐type V‐doped MoSe2 (MoSe2:V) interface layer are fabricated. It is found that the PCE of the device rises from 8.34% to 9.63% as back contact changes from soda lime glass (SLG)/Mo/n‐MoSe2 to SLG/Mo:V/p+‐MoSe2:V. The quantitative analysis demonstrates that the increased PCE predominantly originated from the decreased reverse saturated current density (J0), followed by the decreased series resistance (RS), and lastly by the increased photogenerated current density (JL). The influence mechanism of the SLG/Mo:V/MoSe2:V back contact on device performance is suggested by studying the properties of Mo:V and MoSe2:V films and CZTSSe/MoSe2:V heterojunction. This work emphasizes the vital significance of the back surface passivation field induced by p+‐MoSe2:V/p‐CZTSSe heterojunction, which is enlightening for optimizing the back contact in kesterite photovoltaics.

Improvement of Performance of CZTSSe Solar Cells by the Synergistic Effect of Back Contact Modification and Ag Doping

“…V sheet and Mo target are purchased from Shijiazhuang Huake Metal Material Technology Co., Ltd. According to our previous work, n-type MoSe 2 or p + -type V-doped MoSe 2 (MoSe 2 :V) films can formed on the surface of Mo or Mo:V after selenization . The composition information of Mo and MoSe 2 films with or without V doping is listed in Table S1.…”

“…A VSe 2 or MoO x − intermediate layer with high work function ( W F ) was inserted between the CZTSSe absorber and Mo back electrode to boost hole extraction and reduce the MoSe 2 thickness. A back surface passivation field (BSPF) from CZTSSe toward p-type MoSe 2 was introduced between the CZTSSe absorber and Mo back electrode to boost the hole transport and extraction toward the back electrode. − However, it is difficult to significantly improve the performance of the whole device only by optimizing the quality of the absorber or modifying the interface. It is always expected that the PCE of devices can be enhanced greatly through combining optimization of the bulk absorber and modification of the interfaces.…”