Atomic Layer Deposition of ZnO on InP Quantum Dot Films for Charge Separation, Stabilization, and Solar Cell Formation

Abstract

To improve the stability and carrier mobility of quantum dot (QD) optoelectronic devices, encapsulation or pore infilling processes are advantageous. Atomic layer deposition (ALD) is an ideal technique to infill and overcoat QD films, as it provides excellent control over film growth at the sub‐nanometer scale and results in conformal coatings with mild processing conditions. Different thicknesses of crystalline ZnO films deposited on InP QD films are studied with spectrophotometry and time‐resolved microwave conductivity measurements. High carrier mobilities of 4 cm2 (V s)−1 and charge separation between the QDs and ZnO are observed. Furthermore, the results confirm that the stability of QD thin films is strongly improved when the inorganic ALD coating is applied. Finally, proof‐of‐concept photovoltaic devices of InP QD films are demonstrated with an ALD‐grown ZnO electron extraction layer.

Near‐Infrared Photoactive Semiconductor Quantum Dots for Solar Cells

“…In addition to above-mentioned NBG QDs delivering considerable photovoltaic performance, there are some binary QDs that currently offer petty results with modest PCEs but have development potential, such as SnS, [59,[168][169][170][171] FeS 2 , [60,[172][173][174] Bi 2 S 3 , [175] HgTe, [62,176,177] InAs, [63] InP, [178,179] etc. Table 6 summarizes the recent reports of photovoltaic performance for these potential binary QD-based QDSCs.…”

“…[176] The use of III-V InAs and InP QDs as light harvesting materials yields relatively low PCEs either in sensitized nanocrystalline TiO 2 solar cells or heterojunction devices. [63,178,179] Future optimization of the device interfaces, together with improved quality of QDs, should lead to much enhanced photovoltaic performance.…”

Design Strategy of Quantum Dot Thin‐Film Solar Cells

“…Note that InP QD, one of the III‐V with higher bulk bandgap, when used in solar cell, provides only around 1% efficiency due to inadequate bandgap and insufficient surface treatment. [ 110,111 ] Nevertheless, the development of III‐V QDs for PVs faces numerous obstacles. [ 112,113 ] First, there are numerous trap sites from intractable bonds and surfaces.…”

Barrier reduction and current transport mechanism in Pt/n-InP Schottky diodes using atomic layer deposited ZnO interlayer

“…Recently, Algadi et al employed a 10 nm thick ZnO IL in indium tin oxide (ITO)/InP Schottky photodetectors and they attributed the improved efficiency to the hole barrier by the valence band offset at the ZnO/InP interface [25]. About 14 nm thick ZnO encapsulation layer for InP quantum dots was found to improve the solar cell performance [26]. Zhu et al deposited ZnO/AlN (220 nm/1.9-11.4 nm) stacks on Ti substrate and found the improved piezo-electric performance [27].…”