Highly efficient solution-processed CZTSSe solar cells based on a convenient sodium-incorporated post-treatment method

Na-doping-induced modification of the Cu2ZnSn(S,Se)4/CdS heterojunction towards efficient solar cells

“…However, the CZTSSe efficiency record is only 12.6% whereas the efficiency of CIGS solar cell has recently reached 23.35% [4][5][6]. Recently, people have indeed borrowed some strategies from CIGS to improve the performance of CZTSSe solar cells [2,[7][8][9][10][11][12][13][14][15]. For example, alkali metal doping of CIGS can improve the crystallinity of the absorber [16,17], reduce the density of point defects and increase the P-type carrier concentration [18,19].…”

“…In 2019, Meng et al spun coating ultra-thin NaCl layer on the CZTS precursor film and a power conversion efficiency significantly increased from 9.95% to 11.18%. It promoted the transport of elements, thereby forming a dense CZTSSe thin film with large grains [15]. Maeda et al studied the substitution and migration energies of Na in Cu 2 ZnSnS 4 (CZTS) and CZTSe by first-principles calculations [27].…”

“…As for the doping method, our group used a soft chemical method to dope Na into the CZTSe thin film, which promotes both the growth of the film and the elemental distribution, especially the distribution of Se [22]. Although some theoretical and experi-mental studies have been performed to confirm the positive role of Na in CZTSSe solar cells, the nature of the interaction between Na and efficiency improvement still needs to be studied [15,24].…”

Underlying mechanism of the efficiency loss in CZTSSe solar cells: Disorder and deep defects

“…Performance parameters including short-circuit current density (J SC ), open-circuit voltage (V OC ) and fill factor (FF) of the reported CZTSSe solar cells with efficiencies above 11% are summarized and shown in Fig. 2a-d [13,28,[47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63]. These devices were prepared by different processes, including non-vacuum (i.e., hydrazine-based and non-hydrazine spin coating) and vacuum (i.e., coevaporation, and sputtering) methods.…”

Lithium-assisted synergistic engineering of charge transport both in GBs and GI for Ag-substituted Cu2ZnSn(S,Se)4 solar cells

“…With the increasing demand of power generation market, chalcogenide-based thin film photovoltaic (PV) technologies are highly attractive options due to their low production cost and high conversion efficiency. The earth-abundant kesterite CZTSSe solar cells, sharing similar structure and electrical properties to Cu(In,Ga)Se 2 (CIGS), has been considered as an ideal alternative in the next generation photovoltaics [1][2][3][4][5][6] . Following rapid evolution in bulk, surface and interface engineering, the state-of-theart power conversion efficiency (PCE) has been boosted up to 12.6% [7] , only attaining 80%, 80% and 59% for short-circuit current ( J sc ), fill factor (FF) and open-circuit voltage ( V oc ) of the Shockley-Queisser limit, respectively.…”