Ultra-thin LiF Layer As The Electron Collector For a-Si:H Based Photovoltaic Cell

Abstract

An ultra-thin LiF layer in conjunction with an Al layer is employed as the electron collector for the a-Si:H based single-junction thin film photovoltaic cell. The cell has the structure of boron doped μ-SiOx (hole collector) - intrinsic a-Si:H (photoactive layer) - LiF / Al (electron collector and back electrode). The substrate used is U type Asahi glass, which is also acting as the transparent front electrode. For the cell with the 1.5 nm thick LiF layer, annealed at 120°C, the open current voltage (VOC) of 0.936 V, the short current density (JSC) of 13.598 mA/cm2, and the fill factor (FF) of 0.690 are achieved. The JSC and VOC values are comparable to the values measured for the a-Si:H based p-i-n reference cell, but the FF value is found to be lower, which is attributed to the losses due to recombination at the intrinsic a-Si:H / LiF / Al junction. The current versus voltage measurements are carried out under the standard test conditions. The JSC values are corrected according to the external quantum efficiency measurements of the cells in the AM1.5 spectrum region between 270 nm and 800 nm.

Flexible, Dopant Free a-Si:H Solar Cell

“…After completing the last deposition step, the flexible solar cells are annealed in a conventional oven in ambient air atmosphere for one hour at 120 ] , since the post-deposition annealing treatment at this temperature is found to improve of the -: WAB solar cell with the J WCL [9] and of the -: WAB solar cell with the BCL [10].…”

“…WAB solar cell design with the superstrate structure, a layer of non-stoichiometric molybdenum oxide ( J ) [7]- [9] and a layer of lithium fluoride ( ) [7][8] [10] are used as WCL and BCL respectively. Instead of the rigid and heavy quartz-based substrates used for the rigid, dopant free -: WAB solar cells investigated in our previous works [7][8], a flexible and lightweight transparent substrate is employed for the flexible cell investigated in this work.…”

High Efficiency Dopant Free a-Si:H Solar Cell

“…𝑀𝑜𝑂 , , 𝐿𝑖𝐹, and 𝐴𝑙 can be deposited by PVD. The suitability of 𝐿𝑖𝐹 | 𝐴𝑙 for collecting photogenerated electrons [8], and the suitability of 𝑀𝑜𝑂 , for collecting photogenerated holes [9] were demonstrated. In addition, the proof-of-concept 𝑀𝑖𝐿 cells were processed on planar [10], flexible [11], and cylindrical [12] transparent substrates.…”

“…The solar cell precursors get exposed to air for at least 30 minutes, when they are transported between the PVD and PECVD systems. After completing the final deposition step, 𝑀𝑖𝐿 is annealed at 120 E 𝐶 for one hour in a conventional oven in the air atmosphere, in accordance with the annealing processes developed for achieving high efficiencies for the thin film silicon solar cells with the electron selecting 𝐿𝑖𝐹 CL [8] and / or with the hole selecting 𝑀𝑜𝑂 , CL [9].…”