Over 10% Efficient Cu₂CdSnS₄ Solar Cells Fabricated from Optimized Sulfurization

Abstract

At present, Kesterite-based thin-film solar cells, such as Cu 2 ZnSnS 4 solar cells, involve serious band-tailed states, which leads to low open-circuit voltage, thereby hindering the further improvement of device performance. In stannite-based materials, such as Cu 2 CdSnS 4 , the substitution of Zn with Cd can effectively suppress Cu Cd -related point defects and defect clusters; thus, the band-tailing state is few, which has attracted considerable research attention. In this work, on the basis of using optimized sulfurization and optimizing ratios (Cu/Cd+Sn) and temperatures, Cu 2 CdSnS 4 thin films can be obtained with good quality and single-phase composition, in which the device prepared at a ratio of 0.83 and 590 °C has the highest efficiency. Defect analysis shows that the substitution of Zn with Cd can effectively reduce Cu Cdrelated defects and defect clusters (such as 2Cu Cd +Sn Cd ) and also decrease Urbach energy, fluctuations of bandgap, and electrostatic potential compared with kesterite-based devices. In particular, Cu 2 CdSnS 4 thin-film solar cell prepared under optimized conditions (the ratio of 0.83 and 590 °C) has the minimum reverse saturation current, red shift, and the maximum minority carrier diffusion length. Therefore, an efficiency over 10% Cu 2 CdSnS 4 thin-film solar cell is reported, which shows the highest efficiency among stannitebased solar cells to date.

Grain Growth Mechanism of CZTSSe Films Controlled by the Evaporation Area of Se

“…[10] Despite this, the efficiency of solutionprocessed Cu 2 ZnSn(S, Se) 4 solar cells still remains much lower than the detailed balance limiting efficiency of 32%, which is hindered by the severe nonradiative recombination and large Voc def resulting from the imperfect crystal quality. [11][12][13][14][15] As the most important process affecting the crystallinity of thin CZTSSe films, selenization needs to be further studied. In general, solid Se particles are widely used as Se source for the postselenization of CZTSSe because of the low toxicity and relatively higher safety.…”

Double‐Absorber CZTS/Sb2Se3 Architecture for High‐Efficiency Solar‐Cell Devices

“…[3] Additionally, thin-film sulfide/selenide materials, such as Cu 2 ZnSnS 4 (CZTS) and Sb 2 S 3, are potentially cost-effective owing to the earth-abundant constituent elements. [4][5][6][7][8][9] Realizing high efficiency in low-cost systems is critical to substantiate PV as a future energy source. PV must simultaneously outperform on both the technological and economic fronts.…”

Energy Band Alignment by Solution-Processed Aluminum Doping Strategy toward Record Efficiency in Pulsed Laser-Deposited Kesterite Thin-Film Solar Cell

“…The E g (PL) after Al doping as compared with that of pristine could be due to the increased Al content in kesterite given that the direct correlation of cation to E g has already been identified . In addition, the reduced Δ E g = E g (EQE) – E g (PL) from ≈110 meV (pristine) to ≈50 meV (Al-doped) indicates a suppressed band tailing behavior, which may be due to the reduced Cu–Zn antisite defects in the CZTS absorption layer. ,, …”

“…31 In addition, the reduced ΔE g = E g (EQE) − E g (PL) from ≈110 meV (pristine) to ≈50 meV (Al-doped) indicates a suppressed band tailing behavior, which may be due to the reduced Cu−Zn antisite defects in the CZTS absorption layer. 13,32,33 Further tests have been conducted to illustrate the physical mechanism of the Al-doped device. Another key factor affecting device performance is the band alignment at CZTS/CdS, particularly the conduction band offset (CBO) of the heterojunction.…”