Current Enhancement of CdTe-Based Solar Cells

Abstract

We report on the realization of CdTe solar cell photocurrent enhancement using an n-type CdSe heterojunction partner sputtered on commercial SnO 2 /SnO 2 :F coated soda-lime glass substrates. With high-temperature close-space sublimation CdTe deposition followed by CdCl 2 activation, this thin-film stack allows for substantial interdiffusion at the CdSe/CdTe interface facilitating a CdSe x Te 1 −x alloy formation. The bowing effect causes a reduced optical bandgap of the alloyed absorber layer and, therefore, leads to current enhancement in the long-wavelength region and a decrease in open-circuit voltage (V O C ). To overcome the V O C loss and maintain a high short-circuit current (J S C ), the CdTe cell configuration has been modified using combined CdS:O/CdSe window layers. The new device structure has demonstrated enhanced collection from both short-and long-wavelength regions as well as a V O C improvement. With an optimized synthesis process, a small-area cell using CdS:O/CdSe window layer showed an efficiency of 15.2% with a V O C of 831 mV, a J S C of 26.3 mA/cm 2 , and a fill factor of 69.5%, measured under an AM1.5 illumination without antireflection coating. The results provide new directions for further improvement of CdTe-based solar cells.

The study of CdSe thin film prepared by pulsed laser deposition for CdSe/CdTe solar cell

“…It seems that this weakness may produce a detrimental effect on the CdSe/CdTe PVs, however, the study of Paudel [1] has demonstrated that employing CdSe as a window layer in the CdSe/CdTe solar cells can enhance the response in the region of long wavelength occurred socalled red shift, and also achieve better efficiency. In spite of & Bing Li libing70@126.com the narrow band gap of CdSe thin films, the element Se in the interface of CdSe/CdTe owns a distinct advantage over element S in the interface of CdS/CdTe, because element Se has a better solubility than S in the CdTe layer [4]. Under the high temperature, ternary compound of CdTe x Se 1-x in the interface of CdSe/CdTe can be formed, when Se diffuses into the absorbed CdTe layer.…”

“…Under the high temperature, ternary compound of CdTe x Se 1-x in the interface of CdSe/CdTe can be formed, when Se diffuses into the absorbed CdTe layer. Owing to bowing effects [1,4], the newly formed CdTe x Se 1-x presents a lower band gap E g than that of the only CdTe thin film, which may give rise to an excellent response in the realm of long wavelength up to 910 nm. Like others, the same manners are able to be done to increase the photons of short wavelength by reducing the thickness of CdSe thin films, where the absorption of CdSe thin films for photons can be decreased.…”

“…As reported, there are a variety of manufacture techniques for CdSe thin films, such as magnetron sputtering method [1,4], chemical bath deposition (CBD) [5,6], molecular beam epitaxy (MBE) [7], thermal evaporation [8], pulsed laser deposition (PLD), etc.…”

Interface Engineering for Both Cathode and Anode Enables Low‐Cost Highly Efficient Solution‐Processed CdTe Nanocrystal Solar Cells

“…When the CdSe NC layer is fixed at ≈80 nm (2 layers), the device performance increases first and then decreases linearly with the increase CdS NC layer thickness, indicating the thickness of CdS NC film has a big effect on J sc . It can be concluded that a very thin CdS layer from 0 to 25 nm is attributed to reduce carriers recombination at the interface of ZnO/CdSe, leading to improvement in device performance. However, as the parasitic absorption of CdS layer increases with increasing its thickness, the thick CdS layer from 25 to 100 nm can greatly reduce the spectrum response in short wavelengths, leading to a low J sc .…”

“…It is reported that the energy bandgap as low as 1.32 eV is obtained with x ≈ 0.38 for CdSe x Te 1− x , which is much smaller than 1.5 eV for CdTe . However, devices with a single CdSe ETL may suffer from low V oc and fill factor (FF) due to the large electron injection barrier and interface defects in ZnO/CdSe x Te 1− x , which has been confirmed in the CSS‐processed CdTe solar cells with the SnO 2 /CdSe structure . Thus, new cathode interface strategy should be developed for solution‐processed CdTe NC solar cells.…”