Air photoelectron spectroscopy of 2D perovskites for rational design of stable solar cells with greater than 15% efficiency
Abstract
Their remarkable photo-physical properties of hybrid organic-inorganic metal halide perovskites place them among the most attractive thin-film photovoltaic (PV) technologies that could ultimately approach the theoretical limit for solar cells (~33.5%). A key facto"r for technological exploitation is the longevity and stability of the devices, which is currently limited for the threedimensional""(3D) perovskites. A new approach focuses on two-dimensional (2D) perovskites,which have shown to be able to withstand degradation b""y high temperature, light and moisture. However, in order to utilize 2D perovskites as real solar cells their PCE still needs to be"" improved. The goal of our ONR-funded research is to develop lightweight, high efficiency, highly stable solar cells with high envir"onmental and photo- stability using a new family of materials known as Ruddlesden-Popper (RP) perovskites. We are developing technologicallyviable 2D perovskite materials as solar cell absorbers by applying two concomitant approaches of tailored synthesis and device interface engineering to achieve a power conversion efficiency >15% with stability and ruggedness required for on-field applicat"ions. For both objectives, a detailed understanding of the materials and devices properties is needed. This study is done bycombini""ng various experimental and theoretical tools, available in our lab and in shared facilities. Despite the vast research efforts ther""e is one major electronic property, which is still not directly accessible for us ~ the workfunction of each material. Knowing the w"orkfunction is a crucial step for rational design of materials and devices as it determines how the electronic energy levels in diff"erent materials will align, and hence how much current and voltage could beextracted from a device. Thus, the accurate determinatio"n of the workfunction of the newly discovered 2D perovskite materials is an integral part of this research project. The goal of thi"s proposal is to enable us to equip with a new experimental system based on photoelectron spectroscopy in air (PESA), and scanning k"elvin probe spectroscopy/surface photovoltage spectroscopy (S-KPS/SPVS). PESA is an emerging experimental technique allows to directly measuring the workfunction of various materials at standard conditions. This willallow us to rapidly screen the workfunction of a large number of new materials and rationally match them with the correct electrodes to achieve an optimal energy-level alignment." In addition, the unique capability to determine the energy levels under real operating conditions is very relevant for the device o"ptimization. An important aspect from the blending of these techniques is the ability to understand how the bulk material- characterized individually- interacts with thesubstrate and the various contact layers of the complete device. Combining PESA with SKPS/ SPVS will uniquely enable a complete construction of the electronic band diagram between all the components of the solar cell devices. The new capability will allow deeper understanding a step-by-step deconvolution of the pair interactions among the various layers of the complex multijunction architecture of the devices. It will thus accelerate the path to successfully transition from the fundamental knowledge of electronic properties of the materials to the implementation of this knowledge to the actual solar cells.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 23, 2018
- Source ID
- N000141812102
Entities
People
- Mercouri Kanatzidis
Organizations
- Northwestern University
- Office of Naval Research
- United States Navy