Adam Phillips

• Doctor of Philosophy
• Professor (Associate) at University of Toledo

Indium gallium oxide [(InxGa1−x)2O3] alloys are of interest for a variety opto-electronic applications including photovoltaic devices owing to the ability to control properties through alloy composition. A thorough evaluation of the opto-electronic properties of (InxGa1−x)2O3 (x = 0.71, 0.55, 0.45, 0.36, and 0.28) thin films is obtained by using te...

Tin-lead perovskite solar cells are promising for single-junction and tandem photovoltaics due to their high efficiency and lower environmental impact. However, optimization efforts are hindered by significant discrepancies in reported carrier lifetimes, ranging from nanoseconds to hundreds of microseconds. Here, we address these inconsistencies us...

Perovskite-CdTeSe tandem SCAPS definition file

SCAPS script for tandem simulation

Thin‐film tandem photovoltaic (PV) technology has emerged as a promising avenue to enhance power conversion efficiency beyond the radiative efficiency limit of single‐junction devices. Combining a tunable wide‐bandgap perovskite cell with a commercially established narrow‐bandgap cadmium selenium telluride (CdSeTe) cell in a comparatively easy‐to‐f...

Cadmium telluride (CdTe) solar cells represent a commercially successful photovoltaic technology, with an annual production capacity approaching 20 GW. However, improving the open‐circuit voltage ( V OC ) remains challenging. This study aims to deepen the understanding of charge carrier recombination in CdTe solar cells and to explore alternative d...

High-efficiency, lightweight, and flexible solar cells are sought for a variety of applications particularly when high power density and flexible form factors are desired. Development of solar cells on flexible substrates may also offer production advantages in roll-to-roll or sheet-to-sheet processes. Here, we report device efficiencies of 17.2% a...

Thin film CdTe-based photovoltaic devices have achieved high efficiency above 22 %. The recent improvement in efficiency is due to Se alloying in the CdTe absorbers to form a CdSeTe/CdTe structure. The subsequent band gap grading increases the short circuit current density. The Se can be introduced by depositing a precursor thin film of either CdSe...

There is a great deal of interest in increasing the energy yield from thin film solar cells by implementing bifacial operation. However, deleterious band bending and high interface recombination at the back transparent electrode can cause problems. Here, we investigate how bifacial thin film devices perform when illuminated through the front, back,...

An optical function parameterization of polycrystalline MgxZn1-xO (MZO) thin films as a function of bandgap Eg has been utilized in applications for the metrology of CdTe-based solar cell structures that incorporate MZO thin films as high resistivity transparent (HRT) layers. Parametric expressions are applied to facilitate mapping spectroscopic el...

Our previous work has demonstrated that the formation of a penternary cadmium chalcogenide Cd(O,S,Se,Te) region can significantly reduce the front interface recombination in Cd(Se,Te)-based thin-film solar cells. In this work, we have shown that oxygen management during the device fabrication is crucial to form this region. While both the CdS and C...

In recent years, various lift-off methods have been developed to fabricate lightweight and flexible cadmium telluride (CdTe)-based solar cells. In this work, we report flexible cadmium sulfide (CdS)/CdTe solar cells using a water-assisted lift-off approach. We demonstrate that an additional cadmium chloride treatment for the CdS film is critical to...

Bandgap gradient is a proven approach for improving the open-circuit voltages (VOCs) in Cu(In,Ga)Se2 and Cu(Zn,Sn)Se2 thin-film solar cells, but has not been realized in Cd(Se,Te) thin-film solar cells, a leading thin-film solar cell technology in the photovoltaic market. Here, we demonstrate the realization of a bandgap gradient in Cd(Se,Te) thin-...

In this work, we fabricate antimony sulfoselenide (Sb2(S, Se)3) thin‐film solar cells by a hydrothermal method followed by a post‐deposition annealing process at different temperatures and investigate the impact of the annealing temperature on the morphological, structural, optoelectronic, and defect properties of the hydrothermally grown Sb2(S, Se...

Cadmium telluride (CdTe) is one of the leading technologies in thin-film solar cells; however, its open-circuit voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> ) is limited by defects associated with polycrystalline nature, carrier concentration, and interfaces. To overcome the deep...

Electron selective contacts (emitters) play an important role in minimizing carrier recombination at the front surface of CdTe solar cells through proper band alignments. Magnesium Zinc Oxide (Mg0.2Zn0.8O, (MZO)) is one of the suitable candidates as a front emitter with a bandgap of ~ 3.7 eV, but its stability and device reproducibility are subject...

Bifacial solar cells have the potential to maintain energy output higher than monofacial devices under unfavorable weather conditions. A transparent back‐buffer layer which can passivate the interface and improve the minority carrier lifetime is critical in CdTe based bifacial devices. Here, we demonstrate solution processed CuxCryOz as a promising...

Understanding and controlling the optical and electrical properties of the solar cells, from the absorber layer to the complete devices, is one of the key elements for engineering high-efficiency devices. Such an understanding, especially the correlation between device performance and optical-structural-morphological properties of film stack, is st...

CuInSe2 (CIS) thin-film solar cells in the substrate configuration were fabricated and studied using spectroscopic ellipsometry (SE). Starting with the parameterized complex dielectric functions of the individual component layers, SE analysis was performed using a step-wise procedure that ranks the fitting parameters according to their ability to r...

There are limited choices for front-surface, electron-selective contacts (emitters) for CdTe solar cells, thus hindering scientific and technical development. Here we investigate the photovoltaic performance of devices fabricated with (InxGa1–x)2O3 (IGO) emitters with varying In-to-Ga ratios prepared by cosputtering. In agreement with predictions,...

Employing single-walled carbon nanotubes (SWNTs) as an additive in the active layer of organic photovoltaics (OPV) to improve charge extraction is gaining weight in the research community. While SWNTs can transport charge carriers orders of magnitudes faster than conventional polymers, they also quench excitons and trap free charges, reducing devic...

With high efficiency and fast processing, metal halide perovskite (PK) solar cells promise a new paradigm for low-cost solar power. In addition to single junction device performance that is near...

We report the role of copper iodide (CuI) nanoparticles (NPs) as a hole transport layer (HTL) in cadmium sulfide/ cadmium telluride (CdS/CdTe) photovoltaics. These CuI NPs were prepared using solution processing at room temperature and used to fabricate monofacial and bifacial CdTe solar cells with different back contacts. Using CuI/Au as the back...

Motivated by their utility in CdTe-based thin film photovoltaics (PV) devices, an investigation of thin films of the magnesium-zinc oxide (MgxZn1−xO or MZO) alloy system was undertaken applying spectroscopic ellipsometry (SE). Dominant wurtzite phase MZO thin films with Mg contents in the range 0 ≤ x ≤ 0.42 were deposited on room temperature soda l...

CdSe thickness and Cu doping play significant roles in achieving high efficiency in CdTe solar cells. Using an evaporated CdSe/CdTe device stack to avoid vacuum breaks between deposition of layers, we investigated the role of the CdSe thickness on the device performance. When the CdSe thickness was greater than a critical value the device performan...

Here, we report the application of lead telluride (PbTe) nanowires (NWs) as a passivating layer to cadmium telluride (CdTe) solar cells enhancing the opto-electronic properties and device performance. The PbTe NWs were synthesized using hot injection colloidal method and applied to CdTe films using a spin-coating process. Steady state photoluminesc...

Copper indium diselenide (CuInSe2; CIS) thin film solar cells have been fabricated with absorber layers deposited in a one-stage co-evaporation process at a substrate temperature of T S = 570°C and at different rates, r. The parameters T S and r are the two key variables in a one-stage thermal evaporation process that can be varied for optimization...

Here, we report the solution-based synthesis of CuGaOX thin film, and its optimization for application as a back buffer layer in CdS/CdTe solar cells. The CuGaOX composition was optimized for best results by varying copper source concentration and annealing time post spin-coating. Minority carrier lifetimes and device parameters were recorded. For...

Here, we introduce Aluminum Gallium Oxide (AlGaOx) buffer synthesized through a solution-based approach which passivates the interface recombination in CdTe thin film solar cells. This paper seeks to optimize the performance of the solution based AlGaOx buffer without the use of copper (Cu). The results indicated that diluting AlGaOx solution with...

This report describes the design, construction, and validation of an irradiance and temperature control chamber used to measure temperature-dependent current voltage characteristics of photovoltaic (PV) solar cells under varying conditions in order to reveal fundamental device physics and materials science issues as they relate to terrestrial and s...

We describe a general approach for protecting metal halide perovskite solar cells against degradation in high-humidity environments using a sputtered barrier coating. A SiO2 protective layer, applied to two different types of perovskite solar cells, was deposited without strongly impacting the initial device performance. The degradation of the cell...

Wide bandgap metal halide perovskites materials are of interest for application as top subcells in multijunction devices. In contrast to smaller gap perovskite devices that perform fairly close to their internal Shockley-Queisser limit, wide gap versions show substantial deficits. To understand the origin of the limitations in more detail we simula...

Bifacial solar cells have the potential to increase the energy yield per unit area over traditional monofacial devices without significant added cost, driving $/kWh costs lower and accelerating the adoption of solar photovoltaics. However, the performance of bifacial thin film solar cells significantly lags that achieved by crystalline silicon cell...

The open-circuit voltage (Voc) of CdTe-based photovoltaics may be limited by carrier recombination at interfaces (front or back) or in the absorber layer. Reduction in recombination of a given dominant mechanisms can lead to improved device performance if the remaining mechanisms turn ON in a narrow bias range just below the open circuit voltage. I...

Thin film CdTe superstrate solar cells have been fabricated by sputtering starting from CdS/CdSe front layers deposited on transparent conductor coated glass. The performance of such devices is sensitive to the fabrication details including the temperature-time profile, which leads to CdSe/CdTe interdiffusion and formation of a CdTe 1-x Se x bandga...

Although back-surface passivation plays an important role in high-efficiency photovoltaics, it has not yet been definitively demonstrated for CdTe. Here, we present a solution-based process, which achieves passivation and improved electrical performance when very small amounts of oxidized Al3+ species are deposited at the back surface of CdTe devic...

A promising technology for the future of solar energy is the highly efficient bifacial photovoltaic (PV) cell using perovskite as an absorbing layer. Here we report the environmental impact per energy generated from bifacial perovskite PV cells in single- and multi-junction configurations. To determine the environmental performance of the energy pr...

Optically transparent p-type materials play a critical role in transparent electronics including photovoltaic (PV) devices. P-type sulfide materials offer an alternative to oxides for PV application due to improved hole transport properties. Here, we report the solution-based synthesis of earth-abundant p-type transparent conducting barium copper s...

Evolving materials science and device architectures continue to drive improvements in photovoltaic solar cell performance. Here, we report the synthesis and application of p‐type transparent copper‐zinc‐sulfide (Cu‐Zn‐S) nanocomposite thin films for application as a semi‐transparent back buffer layer for cadmium telluride (CdTe) photovoltaics. Eart...

Here, we report a method using laser beam induced current (LBIC) measurements to ascertain nonresponsive features of photovoltaic devices that are smaller than the measurement beam size. To demonstrate the method, we determine the effective electrical width of laser scribed lines. Laser scribing is a critical process in producing thin-film photovol...

Here, we report an aspect ratio-controlled synthesis of tellurium (Te) nanowires (NWs) utilizing a hot-injection colloidal method. The synthetic method uses low cost materials – specifically, tellurium oxide (TeO2) as the tellurium source, environmentally benign ethylene glycol as a solvent, and ascorbic acid as a reducing agent. Analysis of scanni...

Perovskite solar cells continue to garner significant attention in the field of photovoltaics. As the optoelectronic properties of the absorbers become better understood, attention has turned to more deeply understanding the contribution of charge transport layers for efficient extraction of carriers. Titanium oxide is known to be an effective elec...

We fabricate and characterize methylammonium lead halide perovskite film as a novel back contact to CdTe thin‐film solar cells. We apply ~0.75 μm perovskite film at the interface of CdCl2‐activated and Cu‐doped CdTe surface and complete the device with Au back contact. We use Cu/Au back contact as a reference to compare results with novel back cont...