Control of Defect States of Kesterite Solar Cells to Achieve More Than 11% Power Conversion Efficiency

Abstract

Due to their inherent nature, kesterite solar cells exhibit complex secondary phases and intrinsic lattice defects. As a result, the power conversion efficiencies (PCEs) of kesterites are considerably lower than the theoretical limit. One of the main culprits of limitation is the open-circuit voltage deficiency (V oc def) due to CuZn antisite-related deep defects that originate from the similar ionic radii of constituent elements of Cu and Zn. Partial replacement of Zn with Cd is known to mitigate the defect states from CuZn antisite-related defects. In this regard, we studied the defect physics of Cd-alloying effects on CZTSSe solar cells by varying the Cd/(Cd + Zn) ratio from 0.04 to 0.3. We further investigated Cd-alloyed CZTSSe (CZCTSSe) devices using temperature-dependent admittance spectroscopy, current–voltage characteristics, and time-resolved photoluminescence measurements. Spectroscopic characterization and analysis revealed that the trap energy level, Urbach energy, and band tailing decreased with low Cd alloying (Cd/(Cd + Zn) < 0.08) and increased again with further Cd alloying (Cd/(Cd + Zn) > 0.08) in CZCTSSe absorbers. Experimental results indicate that the alloying amount of Cd has a huge impact on the defect states of absorber films, which dominates the PCE of CZCTSSe solar cells. With fine tuning of the Cd/(Cd + Zn) ratio = 0.06, a CZCTSSe device efficiency of 11.73% was achieved without an antireflection coating using aqueous spray pyrolysis.

Overcoming the limitations of low-bandgap Cu2ZnSn(S,Se)4devices under indoor light conditions: from design to prototype IoT application

“…We compared the estimated activation energy levels with a previous first-principle calculation study and experimental works from literature. 45–50 Accordingly, the estimated defect energy level in the CZTSSe:Ag–Ge sample ( i.e. , 96 meV) was assigned to the shallow acceptor Zn Sn − and Cu Zn − antisite defects that are closer to E v , while the deeper energy level in the undoped CZTSSe device ( i.e.…”

High Efficiency Aqueous Solution Sprayed CIGSSe Solar Cells: Effects of Zr4+‐Alloyed In2S3 Buffer and K‐Alloyed CIGSSe Absorber

“…The entire fabrication procedure for the CIGSSe solar cell has been described elsewhere. [3,50,81,82] Anti-reflection coating and grid patterns were not applied for any of the devices. Solar cell area was made by mechanically scribed, and electrodes were contacted by using probe station as shown in Figure S18 (Supporting Information).…”

Relevance of Ge incorporation to control the physical behaviour of point defects in kesterite

“…3,[18][19][20][21][22][23] Both theoretical and experimental approaches have been used. A wide range of cationic substitutions have been investigated: Cu by Ag, 24,25 Zn by Cd, 24,[26][27][28] Sn by Ge, [28][29][30][31][32] S by Se 4 and doping of both Cu 2 -ZnSnS 4 and Cu 2 ZnSnSe 4 by Na, Li, Ga 33 and Ge 18,[34][35][36] or even using more exotic elements as in ref. 20 .…”