Earth abundant copper-zinc-tin-chalcogenide (CZTSSe) is an important class of material for the development of low cost and sustainable thin film solar cells. The fabrication of CZTSSe solar cells by ...selenization of CZTS nanocrystals is presented. By tuning the composition of the CZTS nanocrystals and developing a robust film coating method, a total area efficiency as high as 7.2% under AM 1.5 illumination and light soaking has been achieved.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Cu2Zn(Sn1− x Ge x )S4 nanocrystals have been synthesized via batch reaction in oleylamine with no additional surfactants present. The nanocrystals are knife-coated on molybdenum substrates and then ...selenized to form a dense layer of Cu2Zn(Sn1− x Ge x )(S,Se)4, which is then used as the photoabsorbing layer in a thin film solar cell. The band gaps of the nanocrystals and the resulting solar cells are demonstrated to be controlled by adjusting the Ge/(Ge+Sn) ratio of the nanocrystal synthesis precursors. Solar cells fabricated from Cu2ZnGeS4 nanocrystal films yielded a power conversion efficiency of 0.51%. However, Cu2Zn(Snx Ge 1− x )S4 nanocrystals with a Ge/(Ge+Sn) ratio 0.7 yielded devices with an efficiency of 6.8% when synthesized to be Cu-poor and Zn-rich. This result opens the possibility of forming Ge gradients to direct minority carriers away from high recombination interfaces and significantly improve the device efficiency of CZTSSe-based solar cells.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Recent developments in the colloidal synthesis of high quality nanocrystals have opened up new routes for the fabrication of low-cost efficient photovoltaic devices. Previously, we demonstrated the ...utility of CuInSe2 nanocrystals in the fabrication of CuInSe2 thin film solar cells. In those devices, sintering the nanocrystal film yields a relatively dense CuInSe2 film with some void space inclusions. Here, we present a general approach toward eliminating void space in sintered nanocrystal films by utilizing reactions that yield a controlled volume expansion of the film. This is demonstrated by first synthesizing a nanocrystal ink composed of Cu(In1−x Ga x )S2 (CIGS). After nanocrystal film formation, the nanocrystals are exposed to selenium vapor during which most of the sulfur is replaced by selenium. Full replacement produces a ∼14.6% volume expansion and reproducibly leads to good dense device-quality CIGSSe absorber films with reduced inclusion of void space. Solar cells made using the CIGSSe absorber films fabricated by this method showed a power conversion efficiency of 4.76% (5.55% based on the active nonshadowed area) under standard AM1.5 illumination.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
The ability to alloy Cu2ZnSn(S,Se)4 with Ge provides a unique ability to band-gap engineer the absorber film by controlling the relative cation ratios. In here, a preliminary study on adjusting the ...Ge to Sn ratio is shown to significantly improve the device performance of CZTSSe thin film solar cells. CZTGeSSe solar cell with total area power conversion efficiency as high as 8.4% has been realized using a nanocrystal-based thin film deposition process. The selenized CZTGeSSe thin film exhibits a bi-layer structure where the thin sintered large-grain layer could be responsible for the poor red-response in external quantum efficiency of the resulting solar cell.
Display omitted
► Solution synthesis of Ge alloyed CZTS nanocrystals for photovoltaic application. ► Selenization of the nanocrystal film results in CZTGeSSe thin films with a bi-layer microstructure. ► Ge alloyed CZTSSe solar cell shows enhanced open circuit voltage, fill factor, and power conversion efficiency.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
CuIn(S,Se)
2 thin film solar cells are fabricated by selenizing CuInS
2 nanocrystals synthesized using a variety of copper and indium precursors. Specifically, copper and indium acetates, ...acetylacetonates, iodides, chlorides and nitrates are investigated to determine the effect of precursors on electronic properties and device performance. Nanocrystal synthesis with each of these precursors can be optimized to yield similar nanocrystal composition, size and structure. In addition, dense chalcopyrite CuIn(S,Se)
2 thin films with micron sized grains at the surface are formed upon selenization regardless of precursor type. Surprisingly, solar cells fabricated from each nanocrystal ink have roughly the same carrier concentrations of 10
16 to 10
17
cm
−
3
in the absorber layer and achieve active area efficiencies of approximately 5%.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Solar cells are fabricated by selenizing CuInS 2 nanocrystals synthesized from various precursors to determine the effect of precursor on device performance. Copper and indium iodides, chlorides, ...acetates, acetylacetonates and nitrates are used to synthesize sphalerite CuInS 2 nanocrystals, which are drop cast onto Mo coated glass. Selenization results in chalcopyrite CuIn(S,Se) 2 films, which are fabricated into devices exhibiting ~5% efficiency regardless of precursor. Variations in nanocrystals are investigated with TEM, XRD and EDS while film formation is studied with SEM and XRD. Devices fabricated with a SLG/Mo/CISSe/CdS/i-ZnO/ITO/Ag structure are studied with JV under simulated AM1.5G, EQE and CV. It is determined that impurities resulting from the choice of nanocrystal synthesis precursor did not significantly limiting device performance during this study.
A generalized and robust method using multinary sulfide nanocrystals for the fabrication Cu(In, Ga)(S, Se) 2 CIGSSe and Cu 2 Zn, Sn(S, Se) 4 CZTSSe thin films and photovoltaic (PV) devices has been ...developed. By direct synthesis of the multinary sulfide nanocrystals with controlled stoichiometry, superior composition uniformity can be achieved inherently. Using standard device structure, PV devices yield total area power conversion efficiencies (PCE) as high as 12.5% and 7.2% for CIGSSe and CZTSSe respectively, under AM1.5 illumination without anti-reflective coating. By incorporating Ge into the CZTS nanocrystal and adjusting the Sn/Ge ratio, band gap optimization of the CZTSSe absorber film can be accomplished. Despite little optimization, CZTGeSSe has yielded promising results by improving the total area PCE to 8.4%.
Recently, numerous non-vacuum methods have been demonstrated for the fabrication of Cu(In x Ga 1-x )Se 2 (CIGSe) thin films and solar cells via selenization of various precursor materials. However, ...composition control and uniformity at all scales remains a challenge. Here we present a promising alternative approach using Cu(In 1-x Ga x )S 2 (CIGS) nanocrystal inks for low cost fabrication of CIGSSe absorber films. By using nanocrystal inks of CIGS as the precursor for selenization, the composition can be controlled at all scales. Nanocrystals with varying Ga concentration can also be used to form graded band gap CIGSSe absorber film. Initial devices fabricated using a graded CIGSSe absorber layer showed a photon to electricity conversion efficiency of 6.23% corresponding to an active area efficiency of 7.10% under AM1.5 illumination.
