Doping-free silicon thin film solar cells using a vanadium pentoxide window layer and a LiF/Al back electrode

Abstract

This work describes the preparation of a doped layer-free hydrogenated amorphous silicon (a-Si:H) thin film solar cell consisting of a vanadium pentoxide (V2O5-x) window layer, an intrinsic a-Si:H absorber layer, and a lithium fluoride (LiF)/aluminum (Al) back electrode. The large difference between the work functions of the V2O5-x layer and the LiF/Al electrode permitted photogenerated carriers in the i-a-Si:H absorber layer to be effectively separated and collected. The effects of the V2O5-x layer thickness and the oxidation states on the photovoltaic performance were investigated in detail. X-ray photoelectron spectroscopy analysis confirmed that the major species of the sputtered V2O5-x thin films were V5+ and V4+. Optimization of the V2O5-x window layer yielded a power conversion efficiency of 7.04%, which was comparable to the power conversion efficiency of a typical a-Si:H solar cell (7.09%).

Replacement of n-type layers with a non-toxic APTES interfacial layer to improve the performance of amorphous Si thin-film solar cells

“…This could be attributed to the low thickness and density of the LiF layer w/o APTES, which might have resulted in a poor thin-lm coverage. 5,9 The addition of APTES with LiF reduced the leakage current and improved the V oc of the devices signicantly, which indicates that the addition of APTES improved the LiF layer density by providing adequate thin-lm coverage and suppressed the charge recombination. Moreover, in terms of device stability enhancement Wang et al 30 presented that the deposition of a thin ($5 nm) APTES SAM could efficiently inhibit the diffusion of metals into adjacent dielectrics and could simultaneously improve the interfacial adhesion.…”

“…7,8 However, the greatest challenge in further development of high performance a-Si:H TFSCs is without (w/o) the involvement of hazardous/toxic doping gases. 5,6,9,10 The fabrication of such devices should be carried out under extremely safe environments. In addition, the use of hazardous/toxic doping gases causes device instabilities because of carrier trapping and the formation of Si dangling bonds.…”

“…5,6 Many alternate processes have been investigated and toxic-free layers have been utilized using various processes in the fabrication of a-Si:H TFSCs. For example, Jung et al 9 demonstrated the deposition of a V 2 O 5Àx window layer using RF magnetron sputtering as an efficient replacement of ptype silicon layer resulting in a power conversion efficiency (PCE) of about 7.04%. Ryu et al 5 presented the scheme for replacement of both p-and n-type layers with MoO 3 and LiF, respectively processed with thermal deposition achieving a PCE of $7.08%.…”

Linking Precursor Alterations to Nanoscale Structure and Optical Transparency in Polymer Assisted Fast-Rate Dip-Coating of Vanadium Oxide Thin Films

“…Metal oxide thin films are an integral part in modern electronic devices and are important in energy storage 1 2 , supercapacitors 3 4 5 , field emission devices 6 7 , photovoltaics 8 , thermochromics 9 10 11 and as components of the working electrodes in sensing devices 12 13 . Improvements in thin film deposition and characterization techniques are of particular interest for high- and low-κ dielectric materials for micro- and nano-electronic devices, where conformal and stoichiometric coatings are required.…”

“…Many phases of VO have applications in areas as intercalation materials 36 , energy storage 37 , electrochromic 38 and thermochromic devices 39 . Solution processed amorphous and crystalline V 2 O 5 thin films have recently been demonstrated as hole transport layers in polymer solar cells where uniform defect free surfaces are required 8 40 41 . By adjusting the crystallisation steps of as-deposited VO from solution processed thin films, it is possible to produce different VO phases in thin film form 9 .…”