Device Postannealing Enabling over 12% Efficient Solution‐Processed Cu₂ZnSnS₄ Solar Cells with Cd²⁺ Substitution

Abstract

Kesterite Cu2ZnSnS4 is a promising photovoltaic material containing low‐cost, earth‐abundant, and stable semiconductor elements. However, the highest power conversion efficiency of thin‐film solar cells based on Cu2ZnSnS4 is only about 11% due to low open‐circuit voltage and fill factor mainly caused by antisite defects and unfavorable heterojunction interface. In this work, a postannealing procedure is proposed to complete a Cd‐alloyed Cu2ZnSnS4 device. The postannealing to complete the device significantly enhances the performance of the indium tin oxide and promotes the moderate interdiffusion of elements between the layers in the device. As a result of the diffusion of Cu, Zn, In, and Sn, the interfacial electron and hole densities are improved, leading to the achievement of a suitable band alignment for carrier transport. The postannealing also reduces the interface traps and deep‐level defects, contributing to decreased nonradiative recombination. Therefore, the open‐circuit voltage and fill factor are both improved, and an efficiency over 12% for pure sulfide‐based kesterite thin‐film solar cells is obtained.

Defect Engineering in Earth‐Abundant Cu2ZnSn(S,Se)4 Photovoltaic Materials via Ga3+‐Doping for over 12% Efficient Solar Cells

“…In general, the C – V is sensitive to the interface traps. [ 6,44 ] With the incorporation of Ga, the N C – V became closer to the Hall results, implying the interface traps (i.e., Cu Zn antisite defect) were eliminated to some extent. The N C – V then achieved a minimum value of 3.91 × 10 16 cm −3 when the R Ga was 7.5%, while the W d increased from 0.213 µm ( R Ga = 0) to a maximum of 0.416 µm ( R Ga = 7.5%).…”

Ag Incorporation with Controlled Grain Growth Enables 12.5% Efficient Kesterite Solar Cell with Open Circuit Voltage Reached 64.2% Shockley–Queisser Limit

“…Kesterite semiconductors, including Cu 2 ZnSnS 4 (CZTS), Cu 2 ZnSnSe 4 (CZTSe), and Cu 2 ZnSn(S,Se) 4 (CZTSSe), are ideal absorber materials for thin film solar cells due to their earth abundant elemental composition and high theoretical efficiency [ 1–5 ] compared to similarly structured chalcopyrite counterpart Cu(In,Ga)Se 2 (CIGS). However, the power conversion efficiency (PCE) of kesterite solar cells is only 12.6%, [ 6,7 ] far lower than that of CIGS, which has reached 23.35%.…”

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].…”