Abstract
The Cu2ZnGe X Sn1‐X S4 (CZGTS) thin‐film solar cells have a limited open‐circuit voltage (V OC) due to bulk and interface recombination. Since the standard CdS buffer layer gives a significant cliff‐like conduction band offset to CZGTS, alternative buffer layers are needed to reduce the interface recombination. This work compares the performance of wide bandgap Cu2ZnGeS4 (CZGS) solar cells fabricated with nontoxic Zn x Sn1–x O y (ZTO) buffer layers grown by atomic layer deposition under different conditions. The V OC of the CZGS solar cell improved significantly to over 1 V by substituting CdS with ZTO. However, V OC is relatively insensitive to ZTO bandgap variations. The short‐circuit current is generally low but is improved with KCN etching of the CZGS absorber before deposition of the ZTO buffer layer. A possible explanation for the device behavior is the presence of an oxide interlayer for nonetched devices.
Highlights
Cu(In,Ga)Se2 solar cells often feature a close to flat conduction band alignment.[14,15] A cliff-like band alignment (CBO < 0) may causeThe Cu2ZnSnS4 (CZTS) has received considerable interest as a promising solar cell material owing to its earth abundance and non-toxicity
A VOC greater than 900 mV was measured on best devices after substituting CdS with ZTO deposited on KCN etched CZGS, compared with below 600 mV for CdS
A record VOC of 1.1 V of non-etched CZGS absorbers was obtained for devices with an atomic layer deposition (ALD) temperature of 100 C, but the VOC was relatively constant for all ZTO deposition temperatures, contrary to expectations
Summary
Cu(In,Ga)Se2 solar cells often feature a close to flat conduction band alignment.[14,15] A cliff-like band alignment (CBO < 0) may cause. The cliff-like band alignment is expected to increase with Ge incorporation due to upward shift in the conduction band minima (CBM) of CZGTS.[18,19,20] This results in an increase in the CBO to %À0.7 eV[19] for the CZGS/CdS interface, which emphasizes the importance of replacing the CdS buffer layer. The ZnxSn1–xOy (ZTO) can be used as an alternative non-toxic substitute for the commonly used CdS buffer layer due to the. The wide bandgap ZTO[22] can reduce the parasitic short wavelength absorption loss compared with the CdS[24] buffer layer. The CZGS can be a potential alternative to expensive wide bandgap GaP(2.3 eV)[25,26] single junction solar cell. Alternative buffer layers have not been investigated for CZGS solar cell application to the best of our knowledge. The effect on PV performance with varying ZTO bandgap energy
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
