Upconversion of 1.54μm radiation in Er³⁺doped fluoride-based materials for c-Si solar cell with improved efficiency

Abstract

Upconverted emission from erbium ions in fluoride materials (glass and disordered crystal of the system CaF2-YF3) are observed in a wide spectral range (from the visible to the near infrared) under infrared excitation at 1.54 μm. In both cases, the upconverted emission in the near infrared (∼1 μm) dominates the spectrum. Absolute UC efficiency defined as the ratio between the UC luminescence power and the absorbed pump power has been experimentally measured. The NIR (∼1 μm) luminescence energy yield for the glass and the disordered crystal varies from 2.4 to 11.5% for the glass and from 7.7 to 16% for the crystal for an infrared excitation power density ranging from 2 W/cm 2 to 100 W/cm 2 . This is of a particular interest for their use as upconverter to improve the c-Si cells quantum efficiency since the energy of the excitation lies below the c-Si absorption edge (1.12 eV at 300 K) and is well located compared to the AM1.5G solar spectrum, outside of the absorption lines due to different atmospheric gases. Furthermore, the most efficient upconverted emission recorded in the investigated materials occurs at an energy just above the gap. A current generated in a bifacial c-Si solar cell is observed when the Er 3+ doped material (1.55 mA and 2.15 mA for the glass and the crystal respectively), placed at the rear face of the cell, is excited at 1.54 μm. The current dependence as a function of the sub-bandgap excitation power has been measured and modelled. Finally the EQE of the complete device is deduced from the measured shortcircuit current and the incident photon flux on the cell. An increase of the cell quantum efficiency of 2.4% and 1.7% is obtained at 1.54 μm with adding the glass and the crystal respectively at the rear face of the c-Si cell. The results are compared to those already obtained with Er: NaYF4 known as the most efficient upconverter. IntrodutionResearches on sustainable energy sources underwent a strong impulse these last years. Among different opportunities, solar energy offers the most abundant sustainable source but, up to now, its use still remains low compared to other sustainable energy sources such as hydraulic, biomass, wind. The main hindrance to a wide development of solar energy has several causes such as the cost of the kWh produced (20−40 cts/kWh), that is in part limited by the efficiency of commercially available solar cells (5−20%) [1]. Important technological breakthroughs only will allow overcoming these difficulties and investigations in this field are directed toward researches on third generation solar cells. Hot carriers, solar concentrators, nanostructured silicon, tandem cells represent the most popular orientations to achieve third generation solar cells. a e-mail: fabienne-pelle@chimie-paristech.frIn these cases, predicted efficiency is drastically improved and may lead to devices with a much higher cost. In this frame, a possibility based on down-(photon cutting) and up-conversion (photon addition) has been proposed. The efficiency increase is provided by a...

Upconversion for Photovoltaics – a Review of Materials, Devices and Concepts for Performance Enhancement

“…In a configuration with the upconverter material attached to the rear of a bifacial silicon solar cell, under 1540 nm excitation with 141 W cm −2 irradiance, an EQE UC of 1.4% was reported for a ZBLAN:4.7% Er 3+ fluoride glass. This performance was quite similar to that of a disordered CaF 2 ‐YF 3 crystal, which achieved 2.4% EQE UC under the same experimental conditions . Due to the high irradiance used, the resulting normalized EQE UC values are rather low, with 1.21 × 10 −4 cm 2 W −1 and 1.7 × 10 −4 cm 2 W −1 , respectively.…”

Up-conversion mechanisms in Er3+-doped fluoroindate glasses under 1550 nm excitation for enhancing photocurrent of crystalline silicon solar cell

“…Although the Er 3+ /Yb 3+ pair is vastly used for enhancing silicon SC efficiency, this work aims to study the strictly management of Er 3+ concentration in a low phonon energy glass to provide an efficient enhancement of SC current through UC emissions under near infrared excitation. The advantages of single Er 3+ doped materials concerning SC applications have already been demonstrated [27][28][29]. In this context, we present the synthesis and evaluation of the UC mechanisms in Er 3+ -doped fluoroindate glasses.…”

Ап-конверсия инфракрасного излучения в щелочно-земельных фторидах, активированных Er-=SUP=-3+-=/SUP=-

“…Поиск эффективных люминофоров, преобразующих ближнее инфракрасное излучение с длиной волны 1−2 µm в свет с длиной волны менее 1 µm, остается актуальной задачей. Ион Er 3+ в кристаллах характеризуется сильным поглощением в области 1.4−1.6 µm, что открывает возможности повышения эффективности кремниевых солнечных батарей за счет регистрации излучения с энергией фотонов меньше ширины запрещенной зоны кремния [1].…”

“…Помимо видимых полос свечения, возбуждение лазерным излучением 1.5 µm приводит к появлению свечения в области 990 nm (CdF 2 −Er [6], CaF 2 −Er [8]), интенсивность которого превышает интенсивности видимых полос. По этой причине некоторые фторидные материалы предлагались для повышения выхода кремниевых фотопреобразователей [1,8,9].…”