Field modulation in Na-incorporated Cu(In,Ga)Se2 (CIGS) polycrystalline films influenced by alloy-hardening and pair-annihilation probabilities

Abstract

The influence of Na on Cu(In,Ga)Se2 (CIGS) solar cells was investigated. A gradient profile of the Na in the CIGS absorber layer can induce an electric field modulation and significantly strengthen the back surface field effect. This field modulation originates from a grain growth model introduced by a combination of alloy-hardening and pair-annihilation probabilities, wherein the Cu supply and Na diffusion together screen the driving force of the grain boundary motion (GBM) by alloy hardening, which indicates a specific GBM pinning by Cu and Na. The pair annihilation between the ubiquitously evolving GBMs has a coincident probability with the alloy-hardening event.PACS: 88. 40. H-, 81. 10. Aj, 81. 40. Cd,

Crystallization behaviour of co-sputtered Cu2ZnSnS4 precursor prepared by sequential sulfurization processes

“…The graded bandgap-induced back-surface field effect, which arises because of the composition dependence of the Ga/(Ga + In) ratio, leads to an increase in the open-circuit voltage (V OC ), fill factor, and short-circuit current density (J SC ) [25,26]. Na incorporation in CIGS films affects their grain growth and preferred orientation, resulting in small grain size and an increase in V OC [27]. Thus, the current level of understanding of CIGS films is fairly high.…”

Structural and Luminescence Properties of Lu2O3:Eu3+ F127 Tri-Block Copolymer Modified Thin Films Prepared by Sol-Gel Method

“…On the other hand, the films present a preferred <111> orientation. The preferential orientation parameter α hkl , is defined as α hkl = I hkl / ΣI hkl , where I hkl is the relative intensity of the corresponding diffraction peak [22,32]. As can be seen in Table 1, the calculated preferential orientation of the Lu 2 O 3 :Eu 3+ F127 modified films increases with the annealing temperature and reaches 97.4% and 84.1% at 1373 K. This behavior is due to the fact that the <111> direction is the lowest surface energy orientation [33,34].…”

Effect of Sodium Treatment on the Performance of Electrostatic Spray Assisted Vapour Deposited Copper-poor Cu(In,Ga)(S,Se) 2 Solar Cells

“…The main improvement after Na incorporation includes the enhancement of crystal structure, electronic characteristics and photovoltaic properties: (i) an increase in grain size and a strong (112) orientation of the CIGS film 25 ; (ii) an increase in the hole concentration and p -type conductivity due to defect passivation 26 ; and (iii) increased open circuit-voltage ( V oc ) due to the enhanced p-type semiconducting characteristics 27 . In addition, there are also reports on the increase in short circuit current ( j sc ) and fill factor (FF) of devices after Na doping 28 . It is noteworthy to mention that if the CIGS absorber becomes more Cu-poor, more dramatic improvement of the Na incorporation on CIGS solar cells can be achieved 29 .…”