Martin Green

• Doctor of Engineering
• Professor at UNSW Sydney

Wide-bandgap kesterite Cu2ZnSnS4 offers an economically viable, sustainably sourced and environmentally friendly material for both single-junction and tandem photovoltaic applications. Nevertheless, since 2018 the record efficiency of such solar cells has stagnated at 11%, largely due to carriers recombining before they are collected. Here we demon...

Silicon solar cell costs are reducing dramatically with these cells now providing the majority of new electricity generation capacity worldwide. Cost reduction has been via economies of scale and steadily increasing sunlight energy conversion efficiency. The best experimental cells at 27.4% efficiency approach the 29.4% figure almost universally re...

The design of high-performance perovskite solar cells (PSCs) for indoor applications requires precise interface engineering to optimize charge extraction, particularly under low-light intensity conditions, where excess carrier density is limited....

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2024 are reviewed.

Cd‐free high‐bandgap Cu2ZnSnS4 (CZTS) solar cells are expected to offer green and low‐cost solutions to single‐junction and tandem photovoltaic markets. Despite attracting considerable attention in past years, reported certified efficiency has yet to exceed the 10% threshold. Sn‐related defects, especially those originating from Sn²⁺ oxidation stat...

Reducing non‐radiative recombination and addressing band alignment mismatches at interfaces remain major challenges in achieving high‐performance wide‐bandgap perovskite solar cells. This study proposes the self‐organization of a thin two‐dimensional (2D) perovskite BA2PbBr4 layer beneath a wide‐bandgap three‐dimensional (3D) perovskite Cs0.17FA0.8...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2024 are reviewed.

Formamidinium lead triiodide (FAPbI3) perovskite without methylammonium and/or Cs cations is considered the most promising candidate for perovskite photovoltaics. However, the crystallization of photoactive α‐FAPbI3 requires high‐temperature annealing (≥150 °C) and a controlled humidity environment when methylammonium‐containing additives are absen...

Currently, single‐layer antireflection coated (SLARC) solar glass has a dominant market share of 95% compared to glass with other coatings or no coating, for Si PV modules. This antireflection coating (ARC) results in an efficiency gain of 2–3%. However, there are issues with these SLARCs: (1) solar cell warming due to increased sub‐bandgap light a...

Kesterite is an earth‐abundant energy material with high predicted power conversion efficiency, making it a sustainable and promising option for photovoltaics. However, a large open circuit voltage Voc deficit due to non‐radiative recombination at intrinsic defects remains a major hurdle, limiting device performance. Incorporating Ge into the keste...

The International Technology Roadmap for Photovoltaics (ITRPV) is a globally recognized annual report discussing and projecting photovoltaic (PV) industry trends. Over the past decade, the silicon PV manufacturing landscape has undergone several rapid changes. By analyzing ITRPV reports from 2012 to 2023, we highlight some key discrepancies between...

The Cd‐free Cu 2 ZnSnS 4 (CZTS) solar cell is an ideal candidate for producing low‐cost clean energy through green materials owing to its inherent environmental friendliness and earth abundance. Nevertheless, sulfide CZTS has long suffered from severe open‐circuit voltage (V OC ) deficits, limiting the full exploitation of performance potential and...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since July 2023 are reviewed.

Decreasing the operating temperature of a photovoltaic (PV) module can increase its electrical output and longevity. This can be achieved by increasing the radiative and convective heat losses on the front or the rear module surface. In this article, we have proposed and investigated, experimentally and numerically, a passive cooling method for the...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2023 are reviewed.

Flexible photovoltaics have been and will be increasingly in demand in modern and future society in various applications. Searching for ideal flexible photovoltaic technologies that can perfectly meet these expanding demands has long been an active branch of photovoltaic research. Flexible kesterite Cu2ZnSn(S,Se)4 (CZTSSe) has emerged in recent yea...

Our study highlights importance elements of the nanoscale intragrain feature that may pave the way to high-efficiency perovskite solar cells.

Semiconductors with multiple anions currently provide a new materials platform from which improved functionality emerges, posing new challenges and opportunities in material science. This review has endeavored to emphasize the versatility of the emerging family of semiconductors consisting of mixed chalcogen and halogen anions, known as "chalcohali...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2022 are reviewed. Graphs showing progress with each cell technology over the 30‐year history of the tables are...

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) with earth‐abundant and environmental‐benign constituents has been regarded as a promising solar energy harvesting material for green and cost‐effective photovoltaic applications. The record efficiency of CZTSSe solar cells has recently been refreshed twice after years‐long stagnation, keeping it in the spotlight....

Understanding carrier loss mechanisms at microscopic regions is imperative for the development of high-performance polycrystalline inorganic thin-film solar cells. Despite the progress achieved for kesterite, a promising environmentally benign and earth-abundant thin-film photovoltaic material, the microscopic carrier loss mechanisms and their impa...

Effectively incorporating alkali metals or alternative isovalent cations into Cu2ZnSnS4 (CZTS) is considered one of the most promising strategies for realizing a step‐change improvement in the photovoltaic device performance. Herein, we successfully manipulate the local distribution of Na and Cd by a moisture‐assisted post‐deposition annealing (MAP...

Sulfide kesterite Cu2ZnSnS4 (CZTS) solar cells, containing earth‐abundant and environmentally benign constituents, are regarded as promising candidates for thin‐film photovoltaic technologies. CZTS device performance, however, is currently limited by severe nonradiative recombination caused by abundant deep‐level defects. Herein, an effective defec...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2022 are reviewed. An appendix describing temporary electrical contacting of large‐area solar cells approach...

Copper (Cu) is present not only in the electrode for inverted-structure halide perovskite solar cells (PSCs) but also in transport layers such as copper iodide (CuI), copper thiocyanate (CuSCN), and copper phthalocyanine (CuPc) alternatives to spiro-OMeTAD due to their improved thermal stability. While Cu or Cu-incorporated materials have been effe...

High operating temperatures have a negative impact on photovoltaic (PV) modules. Hence, lowering the temperature of commercial crystalline silicon modules during their operation becomes increasingly interesting, as it increases the system's energy yield and prolongs the module's lifespan. In this work, we experimentally and numerically investigated...

The persistent double layer structure whereby two layers with different properties form at the front and rear of absorbers is a critical challenge in the field of kesterite thin‐film solar cells, which imposes additional nonradiative recombination in the quasi‐neutral region and potential limitation to the transport of hole carriers. Herein, an eff...

Organic–inorganic metal halide perovskite solar cells represent the fastest advancing solar cell technology in terms of energy conversion efficiency improvement, as seen in the last decade. This has become a promising technology for next-generation, low-cost, high-efficiency photovoltaics including multi-junction tandem cell concepts. Double-juncti...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since June 2021 are reviewed. Consolidated tables showing an extensive listing of the highest independently confirmed effi...

The performance of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) solar cell is known to be severely limited by the nonradiative recombination near the heterojunction interface and within the bulk of the CZTSSe absorber resulting from abundant recombination centers and limited carrier collection efficiency. Herein, nonradiative recombination is simultaneously r...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2021 are reviewed. Consolidated tables showing an extensive listing of the highest independently confirmed e...

The economic value of a photovoltaic installation depends upon both its lifespan and power conversion efficiency. Progress toward the latter includes mechanisms to circumvent the Shockley‐Queisser limit, such as tandem designs and multiple exciton generation (MEG). Here we explain how both silicon tandem and MEG‐enhanced silicon cell architectures...

Earth‐abundant and environmentally benign kesterite Cu2ZnSn(S,Se)4 (CZTSSe) is a promising alternative to its cousin chalcopyrite Cu(In,Ga)(S,Se)2 (CIGS) for photovoltaic applications. However, the power conversion efficiency of CZTSSe solar cells has been stagnant at 12.6% for years, still far lower than that of CIGS (23.35%). In this report, insi...

Lithium incorporation in kesterite Cu2ZnSn(S,Se)4 (CZTSSe) materials has been experimentally proven effective in improving electronic quality for application in photovoltaic devices. Herein, a feasible and effective solution‐based lithium post‐deposition treatment (PDT), enabling further efficiency improvement on the high‐performance baseline is re...

Initial improvement in power conversion efficiency (PCE) during ambient storage is often seen in perovskite solar cells (PSCs). In this work, we studied the origin of PCE enhancement by ambient storage on typical n-i-p PSCs. We found improvements in both fill factor and open-circuit voltage during the first 2 days of storage. By analyzing temperatu...

Dynamics of mobile ions are intimately correlated with the observed slow response in halide perovskites. In article number 2000731 (https://doi.org/10.1002/smtd.202000731), Baohua Jia, Xiaoming Wen and co‐workers review the progress of using photoluminescence micro‐spectroscopy imaging as a unique tool to probe the dynamic processes of mobile ions...

Perovskite solar cells (PSCs) have now achieved power conversion efficiencies (PCEs) over 25%, but their long-term stability under illumination and thermal stress is still a major barrier to commercialisation. Herein, we demonstrate the evaluation of light-induced degradation activation energy (Ea) of encapsulated semi-transparent PSCs by using the...

Majority carrier mobility is one of the most fundamental and yet important carrier transport parameters determining the optimal device architecture and performance of the emerging antimony chalcogenide solar cells. However, carrier mobility measurements based on the Hall effect have limitations for these highly anisotropy materials due to the discr...

Pure sulfide chalcopyrite Cu(In,Ga)S2 (CIGS) is a promising large-band-gap, light-absorbing material for a single-junction cell or the upper cell of tandem solar cells. Current processes for producing such large-band-gap CIGS cells of over 10% efficiency involve use of either toxic cyanide solutions for Cu-rich processes or hazardous H2S gas during...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since June 2020 are reviewed. In this issue, charts showing efficiency improvements since 1993 are included as well as cel...

Supplementary information for the paper "Defect Control for 12.5% Efficiency Cu2ZnSnSe4 Kesterite Thin‐Film Solar Cells by Engineering of Local Chemical Environment"

Kesterite-based Cu2ZnSn(S,Se)4 semiconductors are emerging as promising materials for low-cost, environment-benign, and high-efficiency thin-film photovoltaics. However, the current state-of-the-art Cu2ZnSn(S,Se)4 devices suffer from cation-disordering defects and defect clusters, which generally result in severe potential fluctuation, low minority...

Textured glass is a possible means for reflection reduction of a photovoltaic module. Texturing not only increases the energy yield of the system through reduced reflection losses, but also can play a role in dissipating waste heat through enhancing convective and radiative heat loss. In this work, we describe three textured glass surfaces analytic...

The efficient conversion of solar energy to electricity for human utilization heavily relies on the development of solar cells. Nowadays, a variety of high-performance solar cells are constantly emerging. Thin-film solar cells made from inorganic materials have constituted one of the major categories of solar cells showing potential in the fast gro...

Antimony selenosulfide, Sb2(S,Se)3, has attracted attention over the last few years as a light-harvesting material for photovoltaic technology owing to its phase stability, earth abundancy and low toxicity. However, the lack of a suitable material processing approach to obtain Sb2(S,Se)3 films with optimal optoelectronic properties and morphology s...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2020 are reviewed. Consolidated tables showing an extensive listing of the highest independently confirmed e...

Perovskite decomposition in detail Solar cells are subject to heating when operating in sunlight, and the organic components of hybrid perovskite solar cells, especially the commonly used methylammonium cation, can undergo thermal decomposition. Encapsulation can limit decomposition by bringing such reactions to equilibrium and can prevent exposure...

In article number 2000074, Jangwon Seo and co‐workers address a transparent electrode approach involving surface treatment of the buffer layer, which protects the underlying organic hole transport layer from damage due to sputtering of the transparent conducting oxide. Application of this approach to a four‐terminal tandem configuration with a sili...

The one-dimensional photovoltaic absorber material Sb2S3 requires crystal orientation engineering to enable efficient carrier transport. In this work, we adopted a vapor transport deposition (VTD) method to fabricate vertically aligned Sb2S3 on a CdS buffer layer. Our work shows that such a preferential vertical orientation arises from the sulfur d...

For semitransparent devices with n‐i‐p structures, a metal oxide buffer material is commonly used to protect the organic hole transporting layer from damage due to sputtering of the transparent conducting oxide. Here, a surface treatment approach is addressed for tungsten oxide‐based transparent electrodes through slight modification of the tungste...

Precursor Preparation In article number 1900463, Anita W. Y. Ho‐Baillie and co‐workers report the use of two precursor preparation methods for the deposition of phenethylammonium‐containing organic‐inorganic hybrid perovskite fi lms for photovoltaic a pplications. The fi lm properties, photovoltaic device performance, and stability differ depending...

Environmentally friendly and earth abundant Cu2ZnSnS4 (CZTS) based thin films are potential absorbers for next generation photovoltaics. Their optical properties provide the option to be used as upper cells for Si based tandem solar cells, together with a similar structure to Si, triggering interest in investigation of CZTS/Si tandem cells. However...

For the fabrication of perovskite solar cells (PSCs) using a solution process, it is essential to understand the characteristics of the perovskite precursor solution to achieve high performance and reproducibility. The colloids (iodoplumbates) in the perov-skite precursors under various conditions were investigated by UV-visible absorption, dynamic...

Solar energy is one of the most abundant renewable energy sources. For efficient utilization of solar energy, photovoltaic technology is regarded as the most important source. However, due to the intermittent and unstable characteristics of solar radiation, photoelectric conversion (PC) devices fail to meet the requirements of continuous power outp...

The primary stage of joint formation of silver nanowires (AgNWs) at 60 °C is investigated using rotary scanning transmission electron microscopy (STEM with tomographic reconstruction images), and super large-scale molecular dynamic (MD) simulation (2×106 atoms). This study proves to establish that silver nanowires do not require the conventional hi...

For the fabrication of low‐dimensional perovskite solar cells using hydrophobic bulky organic cation, understanding the effect of precursor preparation on film formation is critical to achieve high quality perovskite film and therefore high energy conversion efficiency in the associated solar device. Herein, we report the use of two methods to prep...

Improving the quality of perovskite poly‐crystalline film is essential for the performance of associated solar cells approaching their theoretical limit efficiency. Pinholes, unwanted defects, and nonperovskite phase can be easily generated during film formation, hampering device performance and stability. Here, a simple method is introduced to pre...

Anti‐Solvent Treatments In article number 1900397, Anita W. Y. Ho‐Baillie and co‐workers report a mixed anti‐solvent treatment by spraying acetonitrile‐added chlorobenzene for the fabrication of high‐quality perovskite films. Although the lower boiling point of acetonitrile preserves the morphology of the perovskite film, it has a significant impac...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since July 2019 are reviewed. Consolidated tables showing an extensive listing of the highest independently confirmed effi...

Theoretical calculation suggests Cu-rich chalcopyrite absorbers contain less defects and have potential to achieve better performance than Cu-poor absorbers. However, this has not been demonstrated due to the detrimental Cu2-xSe impurity remaining in the absorber. Here, we report highly efficient Cu-rich chalcopyrite solar cells by selenizing dimet...

With the rapid development of organic‐inorganic lead halide perovskite photovoltaics, there has been an increasing attention paid to the understanding of growth mechanism for controlling the quality of perovskite films. In this study, we propose a mixed anti‐solvent treatment by spraying acetonitrile (ACN) added chlorobenzene (CBZ) for the fabricat...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined, and new entries since January 2019 are reviewed.

Gas-quenching has been demonstrated to be a robust and reliable method for fabricating perovskite solar cell (PSCs) and is a technique for large area and large-scale production. Although additive engineering has been used to improve various perovskite fabrication methods, it is yet to be utilised by gas-quenching. Herein, we introduce potassium tri...

We investigate the use of distributed Bragg reflectors (DBRs) within triple-junction solar cells (TJSC) for spectrum splitting photovoltaics. An optical model of a lattice-matched (LM) GaInP/GaInAs/Ge TJSC with intermediate DBR is developed, in good agreement with measured reflectance. By modifying the DBR layer number, composition and thickness to...

Single crystalline Ge-rich Si x Ge 1-x epitaxially grown on a Si substrate is attracting great attention for its potential in optical and electronic device applications. One method of achieving Si x Ge 1-x epitaxy is by aluminium-assisted crystallization although the challenge of controlling the Si content in the Si x Ge 1-x is limited by the furna...

This paper provides deep understanding of the formation mechanism of perovskite film fabricated by sequential solution‐based methods. It compares two sequential spin‐coating methods for Cs0.15(MA0.7FA0.3)0.85PbI3 perovskite. First is the “static process,” with a stoppage between the two spin‐coating steps (1st PbI2‐CsI‐dimethyl sulfoxide (DMSO)‐dim...

While interfacial and grain‐boundary passivation presently attract enormous research interest for perovskite solar cells (PSCs), the improvement of Cs‐(FAPbI3)X(MAPbBr3)Y bulk quality still lacks systematical study, especially for constructing polycrystalline layers in planar configurations. Here, a DMSO‐molecule‐process for improving the quality o...

Organic–inorganic metal halide perovskites have gained considerable attention for next-generation photovoltaic cells due to rapid improvement in power conversion efficiencies. However, fundamental understanding of underlying mechanisms related to light- and bias-induced effects at the nanoscale is still required. Here, structural variations of the...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since July 2018 are reviewed.

Increasing the sunlight to electricity conversion efficiency is a key driver for on‐going photovoltaic cost reduction. One of the most successful approaches for improving the efficiency is to split sunlight into suitable spectral bands for a set of solar cells with appropriate energy band gaps. Using this concept, in 2014, our group demonstrated th...

Sulfide kesterite Cu2ZnSnS4 provides an attractive low-cost, environmentally benign and stable photovoltaic material, yet the record power conversion efficiency for such solar cells has been stagnant at around 9% for years. Severe non-radiative recombination within the heterojunction region is a major cause limiting voltage output and overall perfo...

Fluorine-doped tin oxide glass substrate is typically used for state-of-the-art perovskite solar cells (PSCs). However, indium-doped tin oxide (ITO) is better due to higher transparency for a given conductivity, although it has lower tolerance to high-temperature processes required for the compact and mesoporous TiO 2 layers. Here we overcome this...

A UNSW team led by Martin Green achieved a landmark result in photovoltaics in 2014 when it demonstrated the first conversion of sunlight to electricity with efficiency above 40%. Besides this being one of the highest efficiencies ever reported, the work used a method readily accessible to the industry in that an external filter directed a portion...

The earth‐abundant and environmentally‐friendly CuSbS2 solar cells have been struggling with low device performance, especially poor open circuit voltage (Voc). In this work, post‐annealing treatment of the CuSbS2/CdS heterojunction performed on CuSbS2‐based solar cells was firstly reported. With this treatment, we demonstrated CuSbS2 solar cells w...

Consolidated tables showing an extensive listing of the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and new entries since January 2018 are reviewed.