Despite favorable optical properties and band-gap tunability, Cu(In,Ga)S 2 solar cell performance is often limited due to bulk and interface recombination losses. We show that Cu-deficient absorbers have lower bulk recombination, owing to the suppression of the detrimental antisite defects. Zn(O,S) buffer layer further lowers the interface recombination due to appropriate band alignment and suppression of defects at the interface. This leads to a high-quality absorber with lower interface losses, resulting in a high power conversion efficiency of over 15%.
Sb2Se3 has emerged as an important photoelectrochemical (PEC) and photovoltaic (PV) material due to its rapid rise in photoconversion efficiencies. However, Sb2Se3 has a complex defect chemistry, which reduces the maximum photovoltage. Thus, it is important to understand these defects and develop defect passivation strategies in Sb2Se3. A comprehensive investigation of the charge carrier dynamics of Sb2Se3 and the influence of sulfur treatment on its optoelectronic properties is performed using time‐resolved microwave conductivity (TRMC), photoluminescence (PL) spectroscopy, and low‐frequency Raman spectroscopy (LFR). The key finding in this work is that upon sulfur treatment of Sb2Se3, the carrier lifetime is increased by the passivation of deep defects in Sb2Se3 in both the surface region and the bulk, which is evidenced by increased charge carrier lifetime of TRMC decay dynamics, increased radiative recombination efficiency, decreased deep defect level emission (PL), and the emergence of new vibration modes by LFR.
Traditional cadmium sulfide (CdS) buffer layer in selenium-free Cu(In,Ga)S2 solar cells leads to reduced open-circuit voltage because of a negative conduction band offset at the Cu(In,Ga)S2/CdS interface. Reducing this loss necessitates the substitution of CdS by an alternative buffer layer. However, the substitute buffer layer may introduce electrical barriers in the device due to unfavorable band alignment at the other interfaces, such as between buffer/ZnO i-layer. This study aims to reduce interface recombinations and eliminate electrical barriers in Cu(In,Ga)S2 solar cells using a combination of Zn1−x
Mg
x
O and Al-doped Zn1−x
Mg
x
O buffer and i-layer combination deposited using atomic layer deposition and magnetron sputtering, respectively. The devices prepared with these layers are characterized by current–voltage and photoluminescence measurements. Numerical simulations are performed to comprehend the influence of electrical barriers on the device characteristics. An optimal composition of Zn1−x
Mg
x
O (x = 0.27) is identified for a suitable conduction band alignment with Cu(In,Ga)S2 with a bandgap of ∼1.6 eV, suppressing interface recombination and avoiding barriers. Optimized buffer composition together with a suitable i-layer led to a device with 14% efficiency and an open-circuit voltage of 943 mV. A comparison of optoelectronic measurements for devices prepared with zinc oxide (ZnO) and Al:(Zn,Mg)O shows the necessity to replace the ZnO i-layer with Al:(Zn,Mg)O i-layer for a high-efficiency device.
Cu(In,Ga)S2 holds the potential to become a prime candidate for use as the top cell in tandem solar cells owing to its tunable bandgap from 1.55 eV (CuInS2) to 2.50...
Thin film semiconductors
grown using chemical bath methods produce
large amounts of waste solvent and chemicals that then require costly
waste processing. We replace the toxic chemical bath deposited CdS
buffer layer from our Cu(In,Ga)(S,Se)2 (CIGS)-based solar
cells with a benign inkjet-printed and annealed Zn(O,S) layer using
230 000 times less solvent and 64 000 times less chemicals.
The wetting and final thickness of the Zn(O,S) layer on the CIGS is
controlled by a UV ozone treatment and the drop spacing, whereas the
annealing temperature and atmosphere determine the final chemical
composition and band gap. The best solar cell using a Zn(O,S) air-annealed
layer had an efficiency of 11%, which is similar to the best conventional
CdS buffer layer device fabricated in the same batch. Improving the
Zn(O,S) wetting and annealing conditions resulted in the best device
efficiency of 13.5%, showing the potential of this method.
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