10.3% Efficient CuIn(S,Se)₂ Solar Cells from DMF Molecular Solution with the Absorber Selenized under High Argon Pressure

Abstract

Fabricating high performing chalcopyrite absorber material from environmental benign solvent is very important for large scale manufacturing production. Here, N, N‐dimethylformamide (DMF) is used as a single solvent to make CuIn(S,Se)2 (CIS) molecular precursor solution and fabricate CIS absorber material. A power conversion efficiency of 10.3% has been achieved from film selenized under 1.6 atmosphere Ar pressure which is 0% for film selenized under 1 atmosphere pressure. Characterizations using XRD, SEM, TEM, EDX reveal a Cu‐rich absorber material consisting of loosely connected grains with vertical holes in film selenized under 1 atmosphere and a Cu‐poor compact large‐grain top layer with large hole bottom layer in film selenized under high Ar pressure. Further optimization of precursor formulation and device fabrication conditions to address the non‐perfect double layer structure is expected to further improve DMF solution processed CIS solar cell efficiency. Our results demonstrate annealing precursor film under increased atmosphere pressure is a new and promising strategy to fabricate high performing thin film solar cells, which can be applied to all solution processed chalcogenide solar cells including CIS, CIGS and CZTS.

Over 10% Efficient CuIn(S,Se)2 Solar Cells Fabricated From Environmentally Benign Solution in Air

“…At the same time, the decomposition of organic residues releases gas from the surface, resulting in a rough surface with voids/holes in film B. The vertical holes may cause the deposition of CdS in film internal which can act as shunt pathway and lower device performance . The cross‐section SEM images also show that film A has much thicker MoSe 2 layer (about 1800 nm) than film B (about 700 nm), in consistence with the XRD data (Figure a).…”

“…The cycle of coating and annealing was repeated for multiple times to obtain the desired thickness. Then the precursor film was selenized in a tube furnace to form CISSe absorber material according to our previous report . The selenized CISSe film was dipped in (NH 4 ) 2 S aqueous solution to eliminate excess copper selenide, then CdS buffer layer was deposited on top of CISSe film by chemical bath deposition (CBD).…”

“…Many safe and stable solvents such as water, anhydrous alcohol, and propylene glycol have been tried to replace hydrazine but the efficiencies of solar cells fabricated from these solutions are far inferior to that of hydrazine‐based devices . Recently, dimethyl sulfoxide (DMSO) and N , N ‐dimethylformamide (DMF) have been used as solvents to prepare precursor solution and copper indium sulfoselenide (CuIn(S,Se) 2 , CISSe) solar cells with efficiencies above 10% have been reported . Although DMSO and DMF are much less toxic than hydrazine, they are still not the ideal solvents for industrial production.…”

Controllable Formation of Ordered Vacancy Compound for High Efficiency Solution Processed Cu(In,Ga)Se2 Solar Cells

“…However, most of the OVC phases are commonly unintentionally formed because of the Cu‐poor composition in the as‐prepared CIGS thin films. [ 5,18,19 ] In general, the solution based CIGS absorbers are prepared by a rapid one step high‐temperature (around 550 °C) post‐selenization (sulfurization) process. In this process, controlling the distribution of elements along the thickness direction is difficult because of the intense atomic inter‐diffusion.…”

CuZnSn(SxSe1-x)4 Solar Cell Prepared by the Sol-Gel Method Following a Modified Three-Step Selenization Process

“…Thus, this process has been investigated extensively [14,15]. For example, Zhao et al have studied the effect of annealing time and heating rate in ambient Se vapour [16]; Yao et al prepared CZTSSe solar cells by selenization at a low pressure with Se and SnSe 2 sources [17]; Xin et al adopted the absorber selenization process under high argon pressure [18]. Moreover, the selenization process usually results in the formation of a bi-layer structure with bi-modal grain size, which consists of a rough-grain upper layer and a fine-grain bottom layer [11,16,19].…”