Synthesis and characterization of sol gel derived nontoxic CZTS thin films without sulfurization

Abstract

Recently, great attention has been paid to the development of earth rich and nonhazardous Copper Zinc Tin Sulfide (CZTS-Cu 2 ZnSnS 4 ) thin films for application in photovoltaic devices owing to its high absorption coefficient over the visible and infrared region. However, sulfurization process is an indispensable step in growing stoichiometric thin film using conventional physical vapor deposition. Hence, it is imperative to devise a liquid based technique without intentional sulfurization for the optimum quality growth of CZTS thin films. In the current work, layer-bylayer sol-gel deposition technique was utilized to grow high quality CZTS thin films without sulfurization and their structural and optical characteristics were investigated using XRD studies and UV-visible spectroscopy respectively. The morphology and chemical composition of the prepared CZTS films are estimated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis respectively.Highly absorbing and crystalline CZTS films have been successfully grown in the present work which could be further utilized as an absorber layer in photovoltaic applications. K E Y W O R D SCZTS, nontoxic, SEM, sol-gel, UV-visible, XRD | 1195 AMRIT eT Al.

Fabrication of CZTS Films through a Combined Electrodeposition and Solution Process: An Experimental and First‐Principles Study

“…Sulfurization is crucial in CZTS preparation since the conventional sulfurization methods involve use of toxic chemicals and could cause formation of S-based impurities that could hinder the photovoltaic performance of CZTS-based solar cells. [4,[6][7][8][9][16][17][18][19]28] In this context, the present work investigates a straightforward sulfurization procedure, in which electrodeposition is combined with a solution process. At first, the CZT layers were prepared by sequential electrodeposition of Cu, Zn, and Sn at a current density of 0.01 A/cm 2 in the S1, S2, and S3 solutions that detailed in the experimental section (Table 7), respectively.…”

“…Sputtering directly from CZTS alloy targets or co-sputtering methods do not provide the necessary stoichiometry as sulfur remains deficient in vacuum atmosphere due to its high saturation vapor pressure. [4][5][6] Besides, the sputtering rates of different elements are naturally not equal, and secondary phases can nucleate to act as recombination centers, degrading the solar cell performance. [5] In fact, sulfurization is highly influential regarding the resultant performance since the main drawback of CZTS is related to the presence of S-based impurities such as Cu 2 S, Cu 2 SnS 3 , ZnS, and SnS.…”

“…However, H 2 S is a toxic gas and contamination of the reaction medium becomes a prominent issue when the annealing is conducted in S 2 environment. [4,6,[16][17][18][19] Alternatively, electrodeposition might also be used for the sulfurization by introducing various additives such as thiosulfate (Na 2 S 2 O 3 ), thiourea (CH 4 N 2 S), and sulfosalicylic acid (C 7 H 6 O 6 S) as a sulfur source to the electroplating bath. [20][21][22][23] By this way, the subsequent annealing could be conducted in the absence of a S source.…”

“…Variety of precursors could be preferred in the solution process, and the deposition could be performed using dip or spin coating techniques. [4,6,18,24] For instance, Park et al used CuCl 2 , Zn-(CH 3 COO) 2 , SnCl 2 , and thiourea as Cu, Zn, Sn and S source, respectively, and dissolved these in anhydrous 2-methoxyethanol to prepare a sol-gel precursor. [18] The authors showed that a CZTS film containing about 50 % S and with a thickness of 563 nm could be obtained without a subsequent sulfurization when the precursor was prepared with excess thiourea.…”

A Comparative Study: Sequential and Single‐Step‐Electrodeposited CZTS Thin Films

“…[ 1 ] In fact, the bandgap of CZTS matches well with the theoretically predicted ideal bandgap of a semiconductor which can absorb a good part of the solar spectrum and produces good solar cell outputs. [ 2 ] On the other hand, CZTS material has an additional advantage because it can be prepared by several methods such as sputtering, [ 3,4 ] thermal evaporation, [ 5,6 ] spray pyrolysis, [ 7,8 ] sol–gel technique, [ 9,10 ] and electrodeposition. [ 11,12 ] In the literature, it has been reported that PV devices fabricated with CZTS films prepared with different techniques demonstrate the efficiency dependence on growth techniques.…”