Analysis of the Voltage Losses in CZTSSe Solar Cells of Varying Sn Content

Abstract

The performance of kesterite (Cu2ZnSn(S,Se)4, CZTSSe) solar cells is hindered by low open circuit voltage (Voc). The commonly used metric for Voc-deficit, namely, the difference between the absorber band gap and qVoc, is not well-defined for compositionally complex absorbers like kesterite where the bandgap is hard to determine. Here, nonradiative voltage losses are analyzed by measuring the radiative limit of Voc, using external quantum efficiency (EQE) and electroluminescence (EL) spectra, without relying on precise knowledge of the bandgap. The method is applied to a series of Cu2ZnSn(S,Se)4 devices with Sn content variation from 27.6 to 32.9 at. % and a corresponding Voc range from 423 to 465 mV. Surprisingly, the lowest nonradiative loss, and hence the highest external luminescence efficiency (QELED), were obtained for the device with the lowest Voc. The trend is assigned to better interface quality between absorber and CdS buffer layer at lower Sn content.

Efficiency Limits of Underwater Solar Cells

“…Non-radiative recombination, which is usually observed in many organic and inorganic solar cells, is, therefore, not considered directly. [24][25][26] When evaluated at the surface, the detailed balance model yields the classical Shockley-Queisser limit with optimum band-gap values between $ 1:1 and $ 1:4 eV and a maximum efficiency of $ 33% (Figure S1A). 14 As surface waves affect the incoming spectrum just below sea level depending on the weather, 3 the generated power density and efficiency of the underwater solar cells were All calculations were performed at 300 K to allow for a direct comparison with the Shockley-Queisser limit.…”

Defect Control for High‐Efficiency Cu2ZnSn(S,Se)4 Solar Cells by Atomic Layer Deposition of Al2O3 on Precursor Film

“…( V OC,def can be calculated from the bandgap E g and the charge of an electron as , where V OC is obtained from the current density−voltage [ J − V ] analysis under AM 1.5G conditions.) [ 18,19 ] At least in part, large V OC,def is attributed to carrier recombination, [ 20,21 ] which is caused by uncharged or charged defects, [ 22 ] and (or) the coexisting secondary phases in the bulk or interfaces of the absorber layer. [ 23–25 ]…”

Boosting the Efficiency of CZTS/Si Tandem Solar Cells Using In2O3 Layer in CZTS Top Cell

“…[6] Some of the issues for this challenge are currently under investigation such as front buffer optimization, [7] back contact modification [8] and CZTS interface and bulk defects reduction. [9,10] Moreover, Yan et al [11] has reported a V OC of over 710 mV and an increasing of the efficiency (from 5.5% to 6.6%) for CZTS devices using In 2 S 3 /CdS hybrid buffer. These results show that In 2 S 3 /CdS buffers provide a promising way to boost V OC and efficiency of pure sulfide CZTS solar cells.…”