Comparison of Sb, As, and P doping in Cd-rich CdTe single crystals: Doping properties, persistent photoconductivity, and long-term stability

Abstract

Acceptor doping CdTe with group-V elements is promising for increasing the power conversion efficiency of CdTe photovoltaic devices via an increased hole concentration and open circuit voltage (VOC). In past work, we have investigated doping with As in Cd-rich CdTe single crystals grown using the Cd-solvent traveling heater method we have developed. In this study, we compare the doping parameters and stability of hole concentration in the light and dark for P, As, and Sb dopants in crystals cooled very slowly from the growth temperature to approximate thermal equilibrium. In contrast to older reports of a high acceptor ionization energy for Sb, our temperature dependent Hall effect experiments reveal an acceptor ionization energy slightly above 90 meV for Sb doping in the mid 1016 cm−3 range. Room temperature hole concentrations above 1016 cm−3 are observed for P, As, and Sb with each dopant type exhibiting only small changes in hole concentrations over 2 years' time at room temperature. Crystals doped with P, As, or Sb exhibit increased conductivity after above-gap illumination, which decays over periods of minutes to hours depending on temperature. Analysis of the photoconductivity decay reveals a barrier attributed to hole capture of 190–280 meV for the series P, As, and Sb.

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

“…Doping with Cu is limited by compensation 3 , and Cu-doped absorbers can be metastable 4 . Recent progress with Sb, P, and As dopants suggests that ≥ 10 16 cm −3 doping could be achieved 5 – 8 . Because As doping can be used in large-scale photovoltaics manufacturing, it has been the most actively studied 9 , 10 .…”

Sodium Fluoride Doping Approach to CdTe Solar Cells

“…To further improve efficiencies, there has been a shift of research focus away from using copper doping due to strong self-compensation effects which limit hole densities to around 10 15 cm –3 and fast diffusivity which causes long-term stability concerns. , Much of this research has focused on Cd rich growth and doping on the Te site using Group V elements. Phosphorus and arsenic have been effective in achieving high doping densities (>10 16 cm –3 ) with long carrier lifetimes in single crystal CdTe due to high activation ratios despite self-compensation by AX centers, , and more recent efforts have achieved similar doping densities in polycrystalline devices. , …”

“…3,4 Much of this research has focused on Cd rich growth and doping on the Te site using Group V elements. Phosphorus and arsenic have been effective in achieving high doping densities (>10 16 cm −3 ) with long carrier lifetimes in single crystal CdTe due to high activation ratios despite selfcompensation by AX centers, 5,6 and more recent efforts have achieved similar doping densities in polycrystalline devices. 7,8 While Group V doping has shown promise, there has been comparatively few reports of the effects of Group 1A alkali metals on CdTe device performance.…”

Detection of Hg2+ by a Dual-Fluorescence Ratio Probe Constructed with Rare-Earth-Element-Doped Cadmium Telluride Quantum Dots and Fluorescent Carbon Dots

“…Excessive exposure to this ion can cause adverse physiological reactions (such as vomiting, diarrhea, headache, and nausea). Prolonged exposure can lead to kidney failure, liver poisoning, and damage to the human central nervous system. − With the advancement of industrial technology, increasing amounts of Hg 2+ are being used, which inevitably pollute water sources and soil. − Therefore, it is important to detect Hg 2+ present in the environment. − At present, atomic absorption spectroscopy, atomic fluorescence spectrometry, and inductively coupled plasma mass spectrometry (ICP-MS) techniques are used to detect Hg 2+ . − Although these instruments are very accurate and sensitive, they are expensive and complex . These factors limit their widespread use.…”