Joel Jean

Massachusetts Institute of Technology (MIT), Research Laboratory of Electronics, Post-Doc

Stanford University, Electrical Engineering, Alumnus

Massachusetts Institute of Technology (MIT), Electrical Engineering and Computer Science, Alumnus

Followers

162

Following

Public Views

Research focus on quantum dot optoelectronics, solar energy harvesting, and semiconductor device physics.
Supervisors: Vladimir Bulović
Phone: 617-452-5403
Address: 77 Massachusetts Ave., Room 13-3074
Cambridge, MA 02139

less

PROF. OM PRAKASH SINHA

Amity University

Joshua Pearce

Western University Canada

Asha Vijayan

Amrita Vishwa Vidyapeetham

Suseendran Jayachandran

IMEC

Joel Q. Grim

Istituto Italiano di Tecnologia / Italian Institute of Technology

Petra Reinke

University of Virginia

Dusan Danilovic

Ames Laboratory

Irina Kolesnik

Moscow State University

Prof.Dr. İbrahim USLU

Gazi University

Kenneth Vecchio

University of California, San Diego

InterestsView All (19)

Uploads

Papers by Joel Jean

In situ vapor-deposited parylene substrates for ultra-thin, lightweight organic solar cells

Organic Electronics, 2016

Solid-state infrared-to-visible upconversion sensitized by colloidal nanocrystals

Nature Photonics, 2015

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Nano Letters, 2015

Quantum dot photovoltaics (QDPV) offer the potential for low-cost solar cells. To develop strateg... more Quantum dot photovoltaics (QDPV) offer the potential for low-cost solar cells. To develop strategies for continued improvement in QDPVs, a better understanding of the factors that limit their performance is essential. Here, we study carrier recombination processes that limit the power conversion efficiency of PbS QDPVs. We demonstrate the presence of radiative sub-bandgap states and sub-bandgap state filling in operating devices by using photoluminescence (PL) and electroluminescence (EL) spectroscopy. These sub-bandgap states are most likely the origin of the high open-circuit-voltage (VOC) deficit and relatively limited carrier collection that have thus far been observed in QDPVs. Combining these results with our perspectives on recent progress in QDPV, we conclude that eliminating sub-bandgap states in PbS QD films has the potential to show a greater gain than may be attainable by optimization of interfaces between QDs and other materials. We suggest possible future directions that could guide the design of high-performance QDPVs.

Nanostructured architectures for colloidal quantum dot solar cells

Printed Mems Membrane Electrostatic Microspeakers

Pathways for solar photovoltaics

Energy & Environmental Science, Feb 17, 2015

Solar energy is one of the few renewable, low-carbon resources with both the scalability and the ... more Solar energy is one of the few renewable, low-carbon resources with both the scalability and the technological maturity to meet ever-growing global demand for electricity. Among solar power technologies, solar photovoltaics (PV) are the most widely deployed, providing 0.87% of the world's electricity in 2013 and sustaining a compound annual growth rate in cumulative installed capacity of 43% since 2000. Given the massive scale of deployment needed, this article examines potential limits to PV deployment at the terawatt scale, emphasizing constraints on the use of commodity and PV-critical materials. We propose material complexity as a guiding framework for classifying PV technologies, and we analyze three core themes that focus future research and development: efficiency, materials use, and manufacturing complexity and cost.

Download

ZnO Nanowire Arrays for Enhanced Photocurrent in PbS Quantum Dot Solar Cells

Advanced Materials (Deerfield Beach, Fla.), Feb 26, 2013

Vertical arrays of ZnO nanowires can decouple light absorption from carrier collection in PbS qua... more Vertical arrays of ZnO nanowires can decouple light absorption from carrier collection in PbS quantum dot solar cells and increase power conversion efficiencies by 35%. The resulting ordered bulk heterojunction devices achieve short-circuit current densities in excess of 20 mA cm−2 and efficiencies of up to 4.9%.

Download

Graphene Cathode-based ZnO Nanowire Hybrid Solar Cells

Nano Letters, Dec 3, 2012

Growth of semiconducting nanostructures on graphene would open up opportunities for the developme... more Growth of semiconducting nanostructures on graphene would open up opportunities for the development of flexible optoelectronic devices, but challenges remain in preserving the structural and electrical properties of graphene during this process. We demonstrate growth of highly uniform and well-aligned ZnO nanowire arrays on graphene by modifying the graphene surface with conductive polymer interlayers. On the basis of this structure, we then demonstrate graphene cathode-based hybrid solar cells using two different photoactive materials, PbS quantum dots and the conjugated polymer P3HT, with AM 1.5G power conversion efficiencies of 4.2% and 0.5%, respectively, approaching the performance of ITO-based devices with similar architectures. Our method preserves beneficial properties of graphene and demonstrates that it can serve as a viable replacement for ITO in various photovoltaic device configurations.

Download

A model for emission yield from planar photocathodes based on photon-enhanced thermionic emission or negative-electron-affinity photoemission

Journal of Applied Physics, Nov 6, 2012

A general model is presented for electron emission yield from planar photocathodes that accounts ... more A general model is presented for electron emission yield from planar photocathodes that accounts for arbitrary cathode thickness and finite recombination velocities at both front and back surfaces. This treatment is applicable to negative electron affinity emitters as well as positive electron affinity cathodes, which have been predicted to be useful for energy conversion. The emission model is based on a simple one-dimensional steady-state diffusion treatment. The resulting relation for electron yield is used to model emission from thin-film cathodes with material parameters similar to GaAs. Cathode thickness and recombination at the emissive surface are found to strongly affect emission yield from cathodes, yet the magnitude of the effect greatly depends upon the emission mechanism. A predictable optimal film thickness is found from a balance between optical absorption, surface recombination, and emission rate.

Download

Optimization and Characterization of Nanostructured Surfaces for Photon-Enhanced Thermionic Emission and Photoemission cathodes

Bulletin of the American Physical Society, Mar 21, 2011

In the cathode of an energy converter based on photon-enhanced thermionic emission (PETE) photoex... more In the cathode of an energy converter based on photon-enhanced thermionic emission (PETE) photoexcited carriers may need to encounter the emissive surface numerous times before having sufficient thermal energy to escape into vacuum and therefore should be confined close to the surface. However, in a traditional planar geometry, a thin cathode results in incomplete light absorption. Nanostructuring has the potential to increase light capture and boost emission by decoupling the lengths associated with photon absorption and electron emission. Nanostructures may complicate the properties of the emissive surface; therefore, the effect of nanostructuring on emission efficiency needs to be studied.

We have recently reported preliminary theoretical results from a suite of simulation tools to capture the full photoemission process: photon absorption, carrier transport within the active material, and electron ballistics following emission. In this work we use the simulation suite to optimize nanostructures for applications including PETE-based solar energy converters, photodetectors and electron sources. The samples are then characterized, and the emission efficiency measured in an ultra-high vacuum test chamber under application-centric conditions.

In situ vapor-deposited parylene substrates for ultra-thin, lightweight organic solar cells

Organic Electronics, 2016

Solid-state infrared-to-visible upconversion sensitized by colloidal nanocrystals

Nature Photonics, 2015

Open-Circuit Voltage Deficit, Radiative Sub-Bandgap States, and Prospects in Quantum Dot Solar Cells

Nano Letters, 2015