Research Update: Doping ZnO and TiO2 for solar cells

Abstract

ZnO and TiO2 are two of the most commonly used n-type metal oxide semiconductors in new generation solar cells due to their abundance, low-cost, and stability. ZnO and TiO2 can be used as active layers, photoanodes, buffer layers, transparent conducting oxides, hole-blocking layers, and intermediate layers. Doping is essential to tailor the materials properties for each application. The dopants used and their impact in solar cells are reviewed. In addition, the advantages, disadvantages, and commercial potential of the various fabrication methods of these oxides are presented.

Research Update: Atmospheric pressure spatial atomic layer deposition of ZnO thin films: Reactors, doping, and devices

“…Doping is essential for tailoring and optimizing the electronic and optical properties of ZnO. 19 Here, we consider the important properties of ZnO that have been tuned for a variety of device applications.…”

“…11,18,19,25,28,39,50 A particularly effective way of tuning the ZnO conduction band position is through Mg incorporation. 51 This has been achieved by AP-SALD using bis(ethylcyclopentadienyl)magnesium (Mg(CpEt) 2 ) as the magnesium precursor.…”

“…[22][23][24] Furthermore, the use of AP-SALD to control and tune the electronic properties of ZnO through doping is now recognized as a low-cost and scalable way to increase the performance of these devices. 19,20,25 The controlled introduction of dopants by AP-SALD is an important challenge, and the recent progress made for a narrow group of dopants could pave the way for future developments, as the interest in AP-SALD and range of dopants used becomes broader to the level achieved with doped ZnO deposited by conventional ALD. 13 This research update focuses on the deposition of functional ZnO films using AP-SALD.…”

“…13,[19][20][21] ZnO is also an earth-abundant material, has a wide bandgap, and can be processed over large areas, making it suitable for next generation electronics, such as smart window layers, nanorod arrays, and transparent conductors in thin-film solar cells and as switching channels in thin-film transistor (TFT) circuits. 13,19,20,22 Producing ZnO by AP-SALD is very appealing because the high throughput of this technique makes it suitable for devices requiring high production rates, such as in excitonic solar cells. [22][23][24] Furthermore, the use of AP-SALD to control and tune the electronic properties of ZnO through doping is now recognized as a low-cost and scalable way to increase the performance of these devices.…”

Improved Heterojunction Quality in Cu₂O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited <br />Zn_1-xMg_xO

“…11,12 This approach allows the deposition to occur one to two orders of magnitude faster than conventional ALD and outside vacuum, which is compatible with roll-to-roll processing. High quality conformal oxide films produced by AP-SALD can be deposited at low temperatures (<150 °C) on a variety of substrates including plastics, which enables AP-SALD films to be applied to low-cost functional devices such as solar cells 13 , light emitting diodes 14 and thin-film transistors 15 .…”